From af5fa3068a5439af641c64f05e287757f6cb5c1a Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Mon, 26 Jul 2021 11:53:52 -0700
Subject: [PATCH 01/16] Adds `hex_digest` property to LockFileRequests

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 .../pants/backend/experimental/python/lockfile.py | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index 25191b13824..76d9c149411 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -3,6 +3,7 @@
 
 from __future__ import annotations
 
+import hashlib
 import logging
 from dataclasses import dataclass
 from typing import cast
@@ -93,6 +94,20 @@ def from_tool(
             description=f"Generate lockfile for {subsystem.options_scope}",
         )
 
+    @property
+    def hex_digest(self) -> str:
+        """Produces a hex digest of this lockfile's inputs, which should uniquely specify the
+        resolution of this lockfile request.
+
+        Inputs are definted as requirements and interpreter constraints.
+        """
+        m = hashlib.sha256()
+        for requirement in self.requirements:
+            m.update(requirement.encode("utf-8"))
+        for constraint in self.interpreter_constraints:
+            m.update(str(constraint).encode("utf-8"))
+        return m.hexdigest()
+
 
 @rule(desc="Generate lockfile", level=LogLevel.DEBUG)
 async def generate_lockfile(

From 30c1e5193eac8d8dceae7cb20fcef4b124c06197 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Mon, 26 Jul 2021 11:54:18 -0700
Subject: [PATCH 02/16] Adds `lockfile_metadata` functions

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 .../backend/experimental/python/lockfile.py   | 37 +++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index 76d9c149411..3b5f0706e3e 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -287,5 +287,42 @@ async def generate_all_tool_lockfiles(
     return ToolLockGoal(exit_code=0)
 
 
+# Lockfile metadata for headers
+def lockfile_metadata(invalidation_digest: str) -> bytes:
+    """Produces a metadata bytes object for including at the top of a lockfile.
+
+    Currently, this only consists of an invalidation digest for the file, which is used when Pants
+    consumes the lockfile during builds.
+    """
+    return (
+        b"""
+# --- BEGIN LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---
+# invalidation digest: %(invalidation_digest)s
+# --- END LOCKFILE METADATA ---
+    """
+        % {b"invalidation_digest": invalidation_digest.encode("ascii")}
+    ).strip()
+
+
+def read_lockfile_metadata(contents: bytes) -> dict[str, str]:
+    """Reads through `contents`, and returns the contents of the lockfile metadata block as a
+    dictionary."""
+
+    metadata = {}
+    
+    in_metadata_block = False
+    for line in contents.splitlines():
+        line = line.strip()
+        if line == b"# --- BEGIN LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---":
+            in_metadata_block = True
+        elif line == b"# --- END LOCKFILE METADATA ---":
+            break
+        elif in_metadata_block:
+            key, value = (i.strip().decode("ascii") for i in line[1:].split(b":"))
+            metadata[key] = value
+    
+    return metadata
+
+
 def rules():
     return collect_rules()

From b1b656813b182c018030c7aeff12b42886db406e Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Mon, 26 Jul 2021 13:53:04 -0700
Subject: [PATCH 03/16] Adds the invalidation digest header to lockfiles

[ci skip-rust]

[ci skip-build-wheels]
---
 .../backend/experimental/python/lockfile.py   | 32 +++++++++++++++----
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index 3b5f0706e3e..6d771070cc1 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -16,7 +16,14 @@
 from pants.backend.python.util_rules.interpreter_constraints import InterpreterConstraints
 from pants.backend.python.util_rules.pex import PexRequest, PexRequirements, VenvPex, VenvPexProcess
 from pants.engine.addresses import Addresses
-from pants.engine.fs import CreateDigest, Digest, FileContent, MergeDigests, Workspace
+from pants.engine.fs import (
+    CreateDigest,
+    Digest,
+    DigestContents,
+    FileContent,
+    MergeDigests,
+    Workspace,
+)
 from pants.engine.goal import Goal, GoalSubsystem
 from pants.engine.process import ProcessResult
 from pants.engine.rules import Get, MultiGet, collect_rules, goal_rule, rule
@@ -132,7 +139,9 @@ async def generate_lockfile(
         ),
     )
 
-    result = await Get(
+    tmp_lockfile = f"{req.dest}.tmp"
+
+    generated_lockfile = await Get(
         ProcessResult,
         # TODO(#12314): Figure out named_caches for pip-tools. The best would be to share
         #  the cache between Pex and Pip. Next best is a dedicated named_cache.
@@ -143,16 +152,25 @@ async def generate_lockfile(
             argv=[
                 "reqs.txt",
                 "--generate-hashes",
-                f"--output-file={req.dest}",
+                f"--output-file={tmp_lockfile}",
                 # NB: This allows pinning setuptools et al, which we must do. This will become
                 # the default in a future version of pip-tools.
                 "--allow-unsafe",
             ],
             input_digest=input_requirements,
-            output_files=(req.dest,),
+            output_files=(tmp_lockfile,),
         ),
     )
-    return PythonLockfile(result.output_digest, req.dest)
+
+    lockfile_contents = next(
+        iter(await Get(DigestContents, Digest, generated_lockfile.output_digest))
+    )
+    content_with_header = b"%b\n%b" % (lockfile_metadata(req.hex_digest), lockfile_contents.content)
+    complete_lockfile = await Get(
+        Digest, CreateDigest([FileContent(req.dest, content_with_header)])
+    )
+
+    return PythonLockfile(complete_lockfile, req.dest)
 
 
 # --------------------------------------------------------------------------------------
@@ -309,7 +327,7 @@ def read_lockfile_metadata(contents: bytes) -> dict[str, str]:
     dictionary."""
 
     metadata = {}
-    
+
     in_metadata_block = False
     for line in contents.splitlines():
         line = line.strip()
@@ -320,7 +338,7 @@ def read_lockfile_metadata(contents: bytes) -> dict[str, str]:
         elif in_metadata_block:
             key, value = (i.strip().decode("ascii") for i in line[1:].split(b":"))
             metadata[key] = value
-    
+
     return metadata
 
 

From 10632a1474baeda7291cb37e47720a15fe84a064 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Mon, 26 Jul 2021 14:18:41 -0700
Subject: [PATCH 04/16] Change the intermediate filename for nicer-looking
 lockfiles

[ci skip-rust]

[ci skip-build-wheels]
---
 .../pants/backend/experimental/python/lockfile.py     | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index 6d771070cc1..de8b3be5ae3 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -120,8 +120,9 @@ def hex_digest(self) -> str:
 async def generate_lockfile(
     req: PythonLockfileRequest, pip_tools_subsystem: PipToolsSubsystem
 ) -> PythonLockfile:
+    reqs_filename = "reqs.txt"
     input_requirements = await Get(
-        Digest, CreateDigest([FileContent("reqs.txt", "\n".join(req.requirements).encode())])
+        Digest, CreateDigest([FileContent(reqs_filename, "\n".join(req.requirements).encode())])
     )
 
     pip_compile_pex = await Get(
@@ -139,8 +140,6 @@ async def generate_lockfile(
         ),
     )
 
-    tmp_lockfile = f"{req.dest}.tmp"
-
     generated_lockfile = await Get(
         ProcessResult,
         # TODO(#12314): Figure out named_caches for pip-tools. The best would be to share
@@ -150,15 +149,15 @@ async def generate_lockfile(
             description=req.description,
             # TODO(#12314): Wire up all the pip options like indexes.
             argv=[
-                "reqs.txt",
+                reqs_filename,
                 "--generate-hashes",
-                f"--output-file={tmp_lockfile}",
+                f"--output-file={req.dest}",
                 # NB: This allows pinning setuptools et al, which we must do. This will become
                 # the default in a future version of pip-tools.
                 "--allow-unsafe",
             ],
             input_digest=input_requirements,
-            output_files=(tmp_lockfile,),
+            output_files=(req.dest,),
         ),
     )
 

From 71f776f1ab6af219fee00a3aeade102987774910 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Mon, 26 Jul 2021 14:36:44 -0700
Subject: [PATCH 05/16] Factors out "begin lockfile metadata" into constants

[ci skip-rust]

[ci skip-build-wheels]
---
 .../backend/experimental/python/lockfile.py    | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index de8b3be5ae3..29544a1b9ff 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -304,6 +304,10 @@ async def generate_all_tool_lockfiles(
     return ToolLockGoal(exit_code=0)
 
 
+BEGIN_LOCKFILE_HEADER = b"# --- BEGIN LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---"
+END_LOCKFILE_HEADER = b"# --- END LOCKFILE METADATA ---"
+
+
 # Lockfile metadata for headers
 def lockfile_metadata(invalidation_digest: str) -> bytes:
     """Produces a metadata bytes object for including at the top of a lockfile.
@@ -313,11 +317,15 @@ def lockfile_metadata(invalidation_digest: str) -> bytes:
     """
     return (
         b"""
-# --- BEGIN LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---
+%(BEGIN_LOCKFILE_HEADER)b
 # invalidation digest: %(invalidation_digest)s
-# --- END LOCKFILE METADATA ---
+%(END_LOCKFILE_HEADER)b
     """
-        % {b"invalidation_digest": invalidation_digest.encode("ascii")}
+        % {
+            b"BEGIN_LOCKFILE_HEADER": BEGIN_LOCKFILE_HEADER,
+            b"invalidation_digest": invalidation_digest.encode("ascii"),
+            b"END_LOCKFILE_HEADER": END_LOCKFILE_HEADER,
+        }
     ).strip()
 
 
@@ -330,9 +338,9 @@ def read_lockfile_metadata(contents: bytes) -> dict[str, str]:
     in_metadata_block = False
     for line in contents.splitlines():
         line = line.strip()
-        if line == b"# --- BEGIN LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---":
+        if line == BEGIN_LOCKFILE_HEADER:
             in_metadata_block = True
-        elif line == b"# --- END LOCKFILE METADATA ---":
+        elif line == END_LOCKFILE_HEADER:
             break
         elif in_metadata_block:
             key, value = (i.strip().decode("ascii") for i in line[1:].split(b":"))

From 47af3f170385ea8422b3396708785abecda68336 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Tue, 27 Jul 2021 10:05:53 -0700
Subject: [PATCH 06/16] Adds unit tests for lockfile invalidation helpers

[ci skip-rust]

[ci skip-build-wheels]
---
 .../pants/backend/experimental/python/BUILD   |   5 +
 .../backend/experimental/python/lockfile.py   |  12 +-
 .../experimental/python/lockfile_test.py      | 103 ++++++++++++++++++
 3 files changed, 116 insertions(+), 4 deletions(-)
 create mode 100644 src/python/pants/backend/experimental/python/lockfile_test.py

diff --git a/src/python/pants/backend/experimental/python/BUILD b/src/python/pants/backend/experimental/python/BUILD
index 76e8c47837f..765402c9b99 100644
--- a/src/python/pants/backend/experimental/python/BUILD
+++ b/src/python/pants/backend/experimental/python/BUILD
@@ -2,3 +2,8 @@
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 python_library()
+
+python_tests(
+  name = "tests",
+  timeout = 180,
+)
diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index 29544a1b9ff..810c0ffeafd 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -161,10 +161,10 @@ async def generate_lockfile(
         ),
     )
 
-    lockfile_contents = next(
-        iter(await Get(DigestContents, Digest, generated_lockfile.output_digest))
-    )
-    content_with_header = b"%b\n%b" % (lockfile_metadata(req.hex_digest), lockfile_contents.content)
+    _lockfile_contents_iter = await Get(DigestContents, Digest, generated_lockfile.output_digest)
+    lockfile_contents = _lockfile_contents_iter[0]
+
+    content_with_header = validated_lockfile_content(req, lockfile_contents.content)
     complete_lockfile = await Get(
         Digest, CreateDigest([FileContent(req.dest, content_with_header)])
     )
@@ -309,6 +309,10 @@ async def generate_all_tool_lockfiles(
 
 
 # Lockfile metadata for headers
+def validated_lockfile_content(req: PythonLockfileRequest, content: bytes) -> bytes:
+    return b"%b\n%b" % (lockfile_metadata(req.hex_digest), content)
+
+
 def lockfile_metadata(invalidation_digest: str) -> bytes:
     """Produces a metadata bytes object for including at the top of a lockfile.
 
diff --git a/src/python/pants/backend/experimental/python/lockfile_test.py b/src/python/pants/backend/experimental/python/lockfile_test.py
new file mode 100644
index 00000000000..5ff1b149ac7
--- /dev/null
+++ b/src/python/pants/backend/experimental/python/lockfile_test.py
@@ -0,0 +1,103 @@
+# Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from unittest.mock import MagicMock
+
+from pants.backend.experimental.python.lockfile import (
+    PythonLockfileRequest,
+    lockfile_metadata,
+    read_lockfile_metadata,
+    validated_lockfile_content,
+)
+from pants.backend.python.util_rules.interpreter_constraints import InterpreterConstraints
+from pants.util.ordered_set import FrozenOrderedSet
+
+
+def test_metadata_round_trip():
+
+    val = "help_im_trapped_inside_a_unit_test_string"
+    output = read_lockfile_metadata(lockfile_metadata(val))
+    assert val == output["invalidation digest"]
+
+
+def test_validated_lockfile_content():
+
+    req = MagicMock(hex_digest="000faaafcacacaca")
+    content = b"""dave==3.1.4 \\
+    --hash=sha256:cab0c0c0c0c0dadacafec0c0c0c0cafedadabeefc0c0c0c0feedbeeffeedbeef \\
+    """
+
+    line_by_line = lambda b: [ii for i in b.splitlines() if (ii := i.strip())]
+    output = b"""
+# --- BEGIN LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---
+# invalidation digest: 000faaafcacacaca
+# --- END LOCKFILE METADATA ---
+dave==3.1.4 \\
+    --hash=sha256:cab0c0c0c0c0dadacafec0c0c0c0cafedadabeefc0c0c0c0feedbeeffeedbeef \\
+    """
+    assert line_by_line(validated_lockfile_content(req, content)) == line_by_line(output)
+
+
+def test_hex_digest_empty():
+
+    req = PythonLockfileRequest(
+        requirements=FrozenOrderedSet([]),
+        interpreter_constraints=InterpreterConstraints([]),
+        dest="lockfile.py",
+        description="empty",
+    )
+
+    assert req.hex_digest == "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+
+
+def test_hex_digest_empty_interpreter_constraints():
+
+    req = PythonLockfileRequest(
+        requirements=FrozenOrderedSet(
+            [
+                "help",
+                "meim",
+                "trap",
+                "pedi",
+                "naun",
+                "itte",
+            ]
+        ),
+        interpreter_constraints=InterpreterConstraints([]),
+        dest="lockfile.py",
+        description="empty",
+    )
+
+    assert req.hex_digest == "9056af98e88b5f1ce893dcb7d7e189bd813ef4f5009f26594e1499be546fb3e1"
+
+
+def test_hex_digest_empty_requirements():
+
+    req = PythonLockfileRequest(
+        requirements=FrozenOrderedSet([]),
+        interpreter_constraints=InterpreterConstraints(
+            ["stda", "tase", "tand", "itsd", "arka", "ndsc"]
+        ),
+        dest="lockfile.py",
+        description="empty",
+    )
+
+    assert req.hex_digest == "312bd499be026b8ecedb95a3b3e234bdea28e82c2d40ae1b2a435fc20971e2c2"
+
+
+def test_hex_digest_both_specified():
+
+    req = PythonLockfileRequest(
+        requirements=FrozenOrderedSet(["aryi", "nher", "eple", "ases", "avem"]),
+        interpreter_constraints=InterpreterConstraints(
+            [
+                "efro",
+                "mitq",
+                "uick",
+            ]
+        ),
+        dest="lockfile.py",
+        description="empty",
+    )
+
+    assert req.hex_digest == "fc71e036ed72f43b9e0f2dcd37050a9e21773a619f0172ab8b657be9ee502fb6"

From fca64b543ac755feab79f3e8dbdc6b629234f110 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Tue, 27 Jul 2021 10:08:52 -0700
Subject: [PATCH 07/16] Adds comment to explain lambda

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 src/python/pants/backend/experimental/python/lockfile_test.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile_test.py b/src/python/pants/backend/experimental/python/lockfile_test.py
index 5ff1b149ac7..2d5f339a481 100644
--- a/src/python/pants/backend/experimental/python/lockfile_test.py
+++ b/src/python/pants/backend/experimental/python/lockfile_test.py
@@ -27,7 +27,6 @@ def test_validated_lockfile_content():
     --hash=sha256:cab0c0c0c0c0dadacafec0c0c0c0cafedadabeefc0c0c0c0feedbeeffeedbeef \\
     """
 
-    line_by_line = lambda b: [ii for i in b.splitlines() if (ii := i.strip())]
     output = b"""
 # --- BEGIN LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---
 # invalidation digest: 000faaafcacacaca
@@ -35,6 +34,9 @@ def test_validated_lockfile_content():
 dave==3.1.4 \\
     --hash=sha256:cab0c0c0c0c0dadacafec0c0c0c0cafedadabeefc0c0c0c0feedbeeffeedbeef \\
     """
+
+    # Helper function to make the test case more resilient to reformatting
+    line_by_line = lambda b: [ii for i in b.splitlines() if (ii := i.strip())]
     assert line_by_line(validated_lockfile_content(req, content)) == line_by_line(output)
 
 

From 148c29e86e218dfbb4d40649c3c7691a86d152c3 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Tue, 27 Jul 2021 12:09:21 -0700
Subject: [PATCH 08/16] Code review concerns

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 .../backend/experimental/python/lockfile.py   |  4 ++--
 .../experimental/python/lockfile_test.py      | 22 +++++++------------
 2 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index 810c0ffeafd..c911f81945d 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -304,8 +304,8 @@ async def generate_all_tool_lockfiles(
     return ToolLockGoal(exit_code=0)
 
 
-BEGIN_LOCKFILE_HEADER = b"# --- BEGIN LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---"
-END_LOCKFILE_HEADER = b"# --- END LOCKFILE METADATA ---"
+BEGIN_LOCKFILE_HEADER = b"# --- BEGIN PANTS LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---"
+END_LOCKFILE_HEADER = b"# --- END PANTS LOCKFILE METADATA ---"
 
 
 # Lockfile metadata for headers
diff --git a/src/python/pants/backend/experimental/python/lockfile_test.py b/src/python/pants/backend/experimental/python/lockfile_test.py
index 2d5f339a481..cbb7fbaf25e 100644
--- a/src/python/pants/backend/experimental/python/lockfile_test.py
+++ b/src/python/pants/backend/experimental/python/lockfile_test.py
@@ -13,24 +13,22 @@
 from pants.util.ordered_set import FrozenOrderedSet
 
 
-def test_metadata_round_trip():
-
+def test_metadata_round_trip() -> None:
     val = "help_im_trapped_inside_a_unit_test_string"
     output = read_lockfile_metadata(lockfile_metadata(val))
     assert val == output["invalidation digest"]
 
 
-def test_validated_lockfile_content():
-
+def test_validated_lockfile_content() -> None:
     req = MagicMock(hex_digest="000faaafcacacaca")
     content = b"""dave==3.1.4 \\
     --hash=sha256:cab0c0c0c0c0dadacafec0c0c0c0cafedadabeefc0c0c0c0feedbeeffeedbeef \\
     """
 
     output = b"""
-# --- BEGIN LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---
+# --- BEGIN PANTS LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---
 # invalidation digest: 000faaafcacacaca
-# --- END LOCKFILE METADATA ---
+# --- END PANTS LOCKFILE METADATA ---
 dave==3.1.4 \\
     --hash=sha256:cab0c0c0c0c0dadacafec0c0c0c0cafedadabeefc0c0c0c0feedbeeffeedbeef \\
     """
@@ -40,8 +38,7 @@ def test_validated_lockfile_content():
     assert line_by_line(validated_lockfile_content(req, content)) == line_by_line(output)
 
 
-def test_hex_digest_empty():
-
+def test_hex_digest_empty() -> None:
     req = PythonLockfileRequest(
         requirements=FrozenOrderedSet([]),
         interpreter_constraints=InterpreterConstraints([]),
@@ -52,8 +49,7 @@ def test_hex_digest_empty():
     assert req.hex_digest == "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
 
 
-def test_hex_digest_empty_interpreter_constraints():
-
+def test_hex_digest_empty_interpreter_constraints() -> None:
     req = PythonLockfileRequest(
         requirements=FrozenOrderedSet(
             [
@@ -73,8 +69,7 @@ def test_hex_digest_empty_interpreter_constraints():
     assert req.hex_digest == "9056af98e88b5f1ce893dcb7d7e189bd813ef4f5009f26594e1499be546fb3e1"
 
 
-def test_hex_digest_empty_requirements():
-
+def test_hex_digest_empty_requirements() -> None:
     req = PythonLockfileRequest(
         requirements=FrozenOrderedSet([]),
         interpreter_constraints=InterpreterConstraints(
@@ -87,8 +82,7 @@ def test_hex_digest_empty_requirements():
     assert req.hex_digest == "312bd499be026b8ecedb95a3b3e234bdea28e82c2d40ae1b2a435fc20971e2c2"
 
 
-def test_hex_digest_both_specified():
-
+def test_hex_digest_both_specified() -> None:
     req = PythonLockfileRequest(
         requirements=FrozenOrderedSet(["aryi", "nher", "eple", "ases", "avem"]),
         interpreter_constraints=InterpreterConstraints(

From 8a599a1d6df369a52f0c496595ad5357374aef4b Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Wed, 28 Jul 2021 12:05:39 -0700
Subject: [PATCH 09/16] Factors out metadata functions into
 `lockfile_metadata.py`. This will be simpler, I promise.

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 .../backend/experimental/python/lockfile.py   | 52 +-------------
 .../experimental/python/lockfile_metadata.py  | 68 +++++++++++++++++++
 .../experimental/python/lockfile_test.py      |  8 +--
 3 files changed, 73 insertions(+), 55 deletions(-)
 create mode 100644 src/python/pants/backend/experimental/python/lockfile_metadata.py

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index c911f81945d..d754bee5e39 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -33,6 +33,7 @@
 from pants.util.logging import LogLevel
 from pants.util.ordered_set import FrozenOrderedSet
 from pants.util.strutil import pluralize
+from pants.backend.experimental.python.lockfile_metadata import lockfile_content_with_header
 
 logger = logging.getLogger(__name__)
 
@@ -164,7 +165,7 @@ async def generate_lockfile(
     _lockfile_contents_iter = await Get(DigestContents, Digest, generated_lockfile.output_digest)
     lockfile_contents = _lockfile_contents_iter[0]
 
-    content_with_header = validated_lockfile_content(req, lockfile_contents.content)
+    content_with_header = lockfile_content_with_header(req, lockfile_contents.content)
     complete_lockfile = await Get(
         Digest, CreateDigest([FileContent(req.dest, content_with_header)])
     )
@@ -304,54 +305,5 @@ async def generate_all_tool_lockfiles(
     return ToolLockGoal(exit_code=0)
 
 
-BEGIN_LOCKFILE_HEADER = b"# --- BEGIN PANTS LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---"
-END_LOCKFILE_HEADER = b"# --- END PANTS LOCKFILE METADATA ---"
-
-
-# Lockfile metadata for headers
-def validated_lockfile_content(req: PythonLockfileRequest, content: bytes) -> bytes:
-    return b"%b\n%b" % (lockfile_metadata(req.hex_digest), content)
-
-
-def lockfile_metadata(invalidation_digest: str) -> bytes:
-    """Produces a metadata bytes object for including at the top of a lockfile.
-
-    Currently, this only consists of an invalidation digest for the file, which is used when Pants
-    consumes the lockfile during builds.
-    """
-    return (
-        b"""
-%(BEGIN_LOCKFILE_HEADER)b
-# invalidation digest: %(invalidation_digest)s
-%(END_LOCKFILE_HEADER)b
-    """
-        % {
-            b"BEGIN_LOCKFILE_HEADER": BEGIN_LOCKFILE_HEADER,
-            b"invalidation_digest": invalidation_digest.encode("ascii"),
-            b"END_LOCKFILE_HEADER": END_LOCKFILE_HEADER,
-        }
-    ).strip()
-
-
-def read_lockfile_metadata(contents: bytes) -> dict[str, str]:
-    """Reads through `contents`, and returns the contents of the lockfile metadata block as a
-    dictionary."""
-
-    metadata = {}
-
-    in_metadata_block = False
-    for line in contents.splitlines():
-        line = line.strip()
-        if line == BEGIN_LOCKFILE_HEADER:
-            in_metadata_block = True
-        elif line == END_LOCKFILE_HEADER:
-            break
-        elif in_metadata_block:
-            key, value = (i.strip().decode("ascii") for i in line[1:].split(b":"))
-            metadata[key] = value
-
-    return metadata
-
-
 def rules():
     return collect_rules()
diff --git a/src/python/pants/backend/experimental/python/lockfile_metadata.py b/src/python/pants/backend/experimental/python/lockfile_metadata.py
new file mode 100644
index 00000000000..86eeec31a43
--- /dev/null
+++ b/src/python/pants/backend/experimental/python/lockfile_metadata.py
@@ -0,0 +1,68 @@
+# Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from __future__ import annotations
+from typing import TYPE_CHECKING
+
+from dataclasses import dataclass
+
+if TYPE_CHECKING:
+    from pants.backend.experimental.python.lockfile import PythonLockfileRequest
+
+
+BEGIN_LOCKFILE_HEADER = b"# --- BEGIN PANTS LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---"
+END_LOCKFILE_HEADER = b"# --- END PANTS LOCKFILE METADATA ---"
+
+
+@dataclass
+class LockfileMetadata:
+    invalidation_digest: str | None
+
+
+# Lockfile metadata for headers
+def lockfile_content_with_header(req: PythonLockfileRequest, content: bytes) -> bytes:
+    """ Returns a version of the lockfile with a pants metadata header prepended. """
+    return b"%b\n%b" % (lockfile_metadata_header(req.hex_digest), content)
+
+
+def lockfile_metadata_header(invalidation_digest: str) -> bytes:
+    """Produces a metadata bytes object for including at the top of a lockfile.
+
+    Currently, this only consists of an invalidation digest for the file, which is used when Pants
+    consumes the lockfile during builds.
+    """
+    return (
+        b"""
+%(BEGIN_LOCKFILE_HEADER)b
+# invalidation digest: %(invalidation_digest)s
+%(END_LOCKFILE_HEADER)b
+    """
+        % {
+            b"BEGIN_LOCKFILE_HEADER": BEGIN_LOCKFILE_HEADER,
+            b"invalidation_digest": invalidation_digest.encode("ascii"),
+            b"END_LOCKFILE_HEADER": END_LOCKFILE_HEADER,
+        }
+    ).strip()
+
+
+def read_lockfile_metadata(contents: bytes) -> LockfileMetadata:
+    """Reads through `contents`, and returns the contents of the lockfile metadata block as a
+    dictionary."""
+
+    metadata = {}
+
+    in_metadata_block = False
+    for line in contents.splitlines():
+        line = line.strip()
+        if line == BEGIN_LOCKFILE_HEADER:
+            in_metadata_block = True
+        elif line == END_LOCKFILE_HEADER:
+            break
+        elif in_metadata_block:
+            key, value = (i.strip().decode("ascii") for i in line[1:].split(b":"))
+            metadata[key] = value
+
+    return LockfileMetadata(
+        invalidation_digest=metadata.get("invalidation digest")
+    )
+
diff --git a/src/python/pants/backend/experimental/python/lockfile_test.py b/src/python/pants/backend/experimental/python/lockfile_test.py
index cbb7fbaf25e..44dbaf8c899 100644
--- a/src/python/pants/backend/experimental/python/lockfile_test.py
+++ b/src/python/pants/backend/experimental/python/lockfile_test.py
@@ -5,18 +5,16 @@
 
 from pants.backend.experimental.python.lockfile import (
     PythonLockfileRequest,
-    lockfile_metadata,
-    read_lockfile_metadata,
-    validated_lockfile_content,
 )
 from pants.backend.python.util_rules.interpreter_constraints import InterpreterConstraints
 from pants.util.ordered_set import FrozenOrderedSet
+from pants.backend.experimental.python.lockfile_metadata import lockfile_metadata_header, read_lockfile_metadata, validated_lockfile_content
 
 
 def test_metadata_round_trip() -> None:
     val = "help_im_trapped_inside_a_unit_test_string"
-    output = read_lockfile_metadata(lockfile_metadata(val))
-    assert val == output["invalidation digest"]
+    output = read_lockfile_metadata(lockfile_metadata_header(val))
+    assert val == output.invalidation_digest
 
 
 def test_validated_lockfile_content() -> None:

From 7066ab21680f471359c8f1c2a2d95a7b6f18e278 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Wed, 28 Jul 2021 12:26:45 -0700
Subject: [PATCH 10/16] Improves unit tests per code review comments

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 .../experimental/python/lockfile_test.py      | 73 +++++--------------
 1 file changed, 18 insertions(+), 55 deletions(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile_test.py b/src/python/pants/backend/experimental/python/lockfile_test.py
index 44dbaf8c899..9adbbba3d57 100644
--- a/src/python/pants/backend/experimental/python/lockfile_test.py
+++ b/src/python/pants/backend/experimental/python/lockfile_test.py
@@ -1,6 +1,7 @@
 # Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
+import pytest
 from unittest.mock import MagicMock
 
 from pants.backend.experimental.python.lockfile import (
@@ -8,7 +9,7 @@
 )
 from pants.backend.python.util_rules.interpreter_constraints import InterpreterConstraints
 from pants.util.ordered_set import FrozenOrderedSet
-from pants.backend.experimental.python.lockfile_metadata import lockfile_metadata_header, read_lockfile_metadata, validated_lockfile_content
+from pants.backend.experimental.python.lockfile_metadata import lockfile_metadata_header, read_lockfile_metadata, lockfile_content_with_header
 
 
 def test_metadata_round_trip() -> None:
@@ -33,65 +34,27 @@ def test_validated_lockfile_content() -> None:
 
     # Helper function to make the test case more resilient to reformatting
     line_by_line = lambda b: [ii for i in b.splitlines() if (ii := i.strip())]
-    assert line_by_line(validated_lockfile_content(req, content)) == line_by_line(output)
+    assert line_by_line(lockfile_content_with_header(req, content)) == line_by_line(output)
 
 
-def test_hex_digest_empty() -> None:
-    req = PythonLockfileRequest(
-        requirements=FrozenOrderedSet([]),
-        interpreter_constraints=InterpreterConstraints([]),
-        dest="lockfile.py",
-        description="empty",
-    )
-
-    assert req.hex_digest == "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
-
-
-def test_hex_digest_empty_interpreter_constraints() -> None:
-    req = PythonLockfileRequest(
-        requirements=FrozenOrderedSet(
-            [
-                "help",
-                "meim",
-                "trap",
-                "pedi",
-                "naun",
-                "itte",
-            ]
-        ),
-        interpreter_constraints=InterpreterConstraints([]),
-        dest="lockfile.py",
-        description="empty",
-    )
+_interpreter_constraints = [">=3.7", "<3.10"]
+_requirements = ["flake8-pantsbuild>=2.0,<3", "flake8-2020>=1.6.0,<1.7.0"]
 
-    assert req.hex_digest == "9056af98e88b5f1ce893dcb7d7e189bd813ef4f5009f26594e1499be546fb3e1"
-
-
-def test_hex_digest_empty_requirements() -> None:
-    req = PythonLockfileRequest(
-        requirements=FrozenOrderedSet([]),
-        interpreter_constraints=InterpreterConstraints(
-            ["stda", "tase", "tand", "itsd", "arka", "ndsc"]
-        ),
-        dest="lockfile.py",
-        description="empty",
-    )
-
-    assert req.hex_digest == "312bd499be026b8ecedb95a3b3e234bdea28e82c2d40ae1b2a435fc20971e2c2"
-
-
-def test_hex_digest_both_specified() -> None:
+@pytest.mark.parametrize(
+    "requirements,interpreter_constraints,expected",
+    [
+        ([], [], "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"),
+        (_interpreter_constraints, [], "04a2a2691d10bde0a2320bf32e2d40c60d0db511613fabc71933137c87f61500"),
+        ([], _requirements, "4ffd0a2a29407ce3f6bf7bfca60fdfc6f7d6224adda3c62807eb86666edf93bf"),
+        (_interpreter_constraints, _requirements, "6c63e6595f2f6827b6c1b53b186a2fa2020942bbfe989e25059a493b32a8bf36"),
+    ],
+)
+def test_hex_digest(requirements, interpreter_constraints, expected) -> None:
     req = PythonLockfileRequest(
-        requirements=FrozenOrderedSet(["aryi", "nher", "eple", "ases", "avem"]),
-        interpreter_constraints=InterpreterConstraints(
-            [
-                "efro",
-                "mitq",
-                "uick",
-            ]
-        ),
+        requirements=FrozenOrderedSet(requirements),
+        interpreter_constraints=InterpreterConstraints(interpreter_constraints),
         dest="lockfile.py",
         description="empty",
     )
 
-    assert req.hex_digest == "fc71e036ed72f43b9e0f2dcd37050a9e21773a619f0172ab8b657be9ee502fb6"
+    assert req.hex_digest == expected

From 4a489bb91cffb4919cff31fafa2975810a92a0b6 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Wed, 28 Jul 2021 12:33:50 -0700
Subject: [PATCH 11/16] Fixes formatting issues

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 .../backend/experimental/python/lockfile.py   |  2 +-
 .../experimental/python/lockfile_metadata.py  |  9 +++----
 .../experimental/python/lockfile_test.py      | 26 ++++++++++++++-----
 3 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index d754bee5e39..548b70daa7d 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -8,6 +8,7 @@
 from dataclasses import dataclass
 from typing import cast
 
+from pants.backend.experimental.python.lockfile_metadata import lockfile_content_with_header
 from pants.backend.python.subsystems.python_tool_base import (
     PythonToolBase,
     PythonToolRequirementsBase,
@@ -33,7 +34,6 @@
 from pants.util.logging import LogLevel
 from pants.util.ordered_set import FrozenOrderedSet
 from pants.util.strutil import pluralize
-from pants.backend.experimental.python.lockfile_metadata import lockfile_content_with_header
 
 logger = logging.getLogger(__name__)
 
diff --git a/src/python/pants/backend/experimental/python/lockfile_metadata.py b/src/python/pants/backend/experimental/python/lockfile_metadata.py
index 86eeec31a43..f0b6381ea60 100644
--- a/src/python/pants/backend/experimental/python/lockfile_metadata.py
+++ b/src/python/pants/backend/experimental/python/lockfile_metadata.py
@@ -2,9 +2,9 @@
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
 from __future__ import annotations
-from typing import TYPE_CHECKING
 
 from dataclasses import dataclass
+from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
     from pants.backend.experimental.python.lockfile import PythonLockfileRequest
@@ -21,7 +21,7 @@ class LockfileMetadata:
 
 # Lockfile metadata for headers
 def lockfile_content_with_header(req: PythonLockfileRequest, content: bytes) -> bytes:
-    """ Returns a version of the lockfile with a pants metadata header prepended. """
+    """Returns a version of the lockfile with a pants metadata header prepended."""
     return b"%b\n%b" % (lockfile_metadata_header(req.hex_digest), content)
 
 
@@ -62,7 +62,4 @@ def read_lockfile_metadata(contents: bytes) -> LockfileMetadata:
             key, value = (i.strip().decode("ascii") for i in line[1:].split(b":"))
             metadata[key] = value
 
-    return LockfileMetadata(
-        invalidation_digest=metadata.get("invalidation digest")
-    )
-
+    return LockfileMetadata(invalidation_digest=metadata.get("invalidation digest"))
diff --git a/src/python/pants/backend/experimental/python/lockfile_test.py b/src/python/pants/backend/experimental/python/lockfile_test.py
index 9adbbba3d57..00b188af87c 100644
--- a/src/python/pants/backend/experimental/python/lockfile_test.py
+++ b/src/python/pants/backend/experimental/python/lockfile_test.py
@@ -1,19 +1,22 @@
 # Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-import pytest
 from unittest.mock import MagicMock
 
-from pants.backend.experimental.python.lockfile import (
-    PythonLockfileRequest,
+import pytest
+
+from pants.backend.experimental.python.lockfile import PythonLockfileRequest
+from pants.backend.experimental.python.lockfile_metadata import (
+    lockfile_content_with_header,
+    lockfile_metadata_header,
+    read_lockfile_metadata,
 )
 from pants.backend.python.util_rules.interpreter_constraints import InterpreterConstraints
 from pants.util.ordered_set import FrozenOrderedSet
-from pants.backend.experimental.python.lockfile_metadata import lockfile_metadata_header, read_lockfile_metadata, lockfile_content_with_header
 
 
 def test_metadata_round_trip() -> None:
-    val = "help_im_trapped_inside_a_unit_test_string"
+    val = "help_i_am_trapped_inside_a_unit_test_string"
     output = read_lockfile_metadata(lockfile_metadata_header(val))
     assert val == output.invalidation_digest
 
@@ -40,13 +43,22 @@ def test_validated_lockfile_content() -> None:
 _interpreter_constraints = [">=3.7", "<3.10"]
 _requirements = ["flake8-pantsbuild>=2.0,<3", "flake8-2020>=1.6.0,<1.7.0"]
 
+
 @pytest.mark.parametrize(
     "requirements,interpreter_constraints,expected",
     [
         ([], [], "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"),
-        (_interpreter_constraints, [], "04a2a2691d10bde0a2320bf32e2d40c60d0db511613fabc71933137c87f61500"),
+        (
+            _interpreter_constraints,
+            [],
+            "04a2a2691d10bde0a2320bf32e2d40c60d0db511613fabc71933137c87f61500",
+        ),
         ([], _requirements, "4ffd0a2a29407ce3f6bf7bfca60fdfc6f7d6224adda3c62807eb86666edf93bf"),
-        (_interpreter_constraints, _requirements, "6c63e6595f2f6827b6c1b53b186a2fa2020942bbfe989e25059a493b32a8bf36"),
+        (
+            _interpreter_constraints,
+            _requirements,
+            "6c63e6595f2f6827b6c1b53b186a2fa2020942bbfe989e25059a493b32a8bf36",
+        ),
     ],
 )
 def test_hex_digest(requirements, interpreter_constraints, expected) -> None:

From 08ee67b74293bf175ec1b3920de59af6366213d5 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Wed, 28 Jul 2021 12:48:34 -0700
Subject: [PATCH 12/16] Removes cicrular dependency in `lockfile_metadata`

[ci skip-rust]

[ci skip-build-wheels]
---
 .../pants/backend/experimental/python/lockfile.py     |  2 +-
 .../backend/experimental/python/lockfile_metadata.py  | 11 +++--------
 .../backend/experimental/python/lockfile_test.py      |  7 +++----
 3 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index 548b70daa7d..a3e4c9667d4 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -165,7 +165,7 @@ async def generate_lockfile(
     _lockfile_contents_iter = await Get(DigestContents, Digest, generated_lockfile.output_digest)
     lockfile_contents = _lockfile_contents_iter[0]
 
-    content_with_header = lockfile_content_with_header(req, lockfile_contents.content)
+    content_with_header = lockfile_content_with_header(req.hex_digest, lockfile_contents.content)
     complete_lockfile = await Get(
         Digest, CreateDigest([FileContent(req.dest, content_with_header)])
     )
diff --git a/src/python/pants/backend/experimental/python/lockfile_metadata.py b/src/python/pants/backend/experimental/python/lockfile_metadata.py
index f0b6381ea60..db37d70ff11 100644
--- a/src/python/pants/backend/experimental/python/lockfile_metadata.py
+++ b/src/python/pants/backend/experimental/python/lockfile_metadata.py
@@ -4,11 +4,6 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from pants.backend.experimental.python.lockfile import PythonLockfileRequest
-
 
 BEGIN_LOCKFILE_HEADER = b"# --- BEGIN PANTS LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---"
 END_LOCKFILE_HEADER = b"# --- END PANTS LOCKFILE METADATA ---"
@@ -20,9 +15,9 @@ class LockfileMetadata:
 
 
 # Lockfile metadata for headers
-def lockfile_content_with_header(req: PythonLockfileRequest, content: bytes) -> bytes:
+def lockfile_content_with_header(invalidation_digest: str, content: bytes) -> bytes:
     """Returns a version of the lockfile with a pants metadata header prepended."""
-    return b"%b\n%b" % (lockfile_metadata_header(req.hex_digest), content)
+    return b"%b\n%b" % (lockfile_metadata_header(invalidation_digest), content)
 
 
 def lockfile_metadata_header(invalidation_digest: str) -> bytes:
@@ -47,7 +42,7 @@ def lockfile_metadata_header(invalidation_digest: str) -> bytes:
 
 def read_lockfile_metadata(contents: bytes) -> LockfileMetadata:
     """Reads through `contents`, and returns the contents of the lockfile metadata block as a
-    dictionary."""
+    `LockfileMetadata` object."""
 
     metadata = {}
 
diff --git a/src/python/pants/backend/experimental/python/lockfile_test.py b/src/python/pants/backend/experimental/python/lockfile_test.py
index 00b188af87c..929c67b486b 100644
--- a/src/python/pants/backend/experimental/python/lockfile_test.py
+++ b/src/python/pants/backend/experimental/python/lockfile_test.py
@@ -1,8 +1,6 @@
 # Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-from unittest.mock import MagicMock
-
 import pytest
 
 from pants.backend.experimental.python.lockfile import PythonLockfileRequest
@@ -22,7 +20,6 @@ def test_metadata_round_trip() -> None:
 
 
 def test_validated_lockfile_content() -> None:
-    req = MagicMock(hex_digest="000faaafcacacaca")
     content = b"""dave==3.1.4 \\
     --hash=sha256:cab0c0c0c0c0dadacafec0c0c0c0cafedadabeefc0c0c0c0feedbeeffeedbeef \\
     """
@@ -37,7 +34,9 @@ def test_validated_lockfile_content() -> None:
 
     # Helper function to make the test case more resilient to reformatting
     line_by_line = lambda b: [ii for i in b.splitlines() if (ii := i.strip())]
-    assert line_by_line(lockfile_content_with_header(req, content)) == line_by_line(output)
+    assert line_by_line(lockfile_content_with_header("000faaafcacacaca", content)) == line_by_line(
+        output
+    )
 
 
 _interpreter_constraints = [">=3.7", "<3.10"]

From 324dd0e8725a27432b7345eaa6c6acb773ebca92 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Wed, 28 Jul 2021 12:56:30 -0700
Subject: [PATCH 13/16] Remove walrus

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 src/python/pants/backend/experimental/python/lockfile_test.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile_test.py b/src/python/pants/backend/experimental/python/lockfile_test.py
index 929c67b486b..1b4dd281be4 100644
--- a/src/python/pants/backend/experimental/python/lockfile_test.py
+++ b/src/python/pants/backend/experimental/python/lockfile_test.py
@@ -33,7 +33,7 @@ def test_validated_lockfile_content() -> None:
     """
 
     # Helper function to make the test case more resilient to reformatting
-    line_by_line = lambda b: [ii for i in b.splitlines() if (ii := i.strip())]
+    line_by_line = lambda b: [i for i in (j.strip() for j in b.splitlines()) if i]
     assert line_by_line(lockfile_content_with_header("000faaafcacacaca", content)) == line_by_line(
         output
     )

From ba02a9a70d135a146638f6e046571d5e17d54bca Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Wed, 28 Jul 2021 13:06:28 -0700
Subject: [PATCH 14/16] Renamed `lockfile_test.py`

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 .../python/{lockfile_test.py => lockfile_metadata_test.py}        | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename src/python/pants/backend/experimental/python/{lockfile_test.py => lockfile_metadata_test.py} (100%)

diff --git a/src/python/pants/backend/experimental/python/lockfile_test.py b/src/python/pants/backend/experimental/python/lockfile_metadata_test.py
similarity index 100%
rename from src/python/pants/backend/experimental/python/lockfile_test.py
rename to src/python/pants/backend/experimental/python/lockfile_metadata_test.py

From 1d517fc11890d9e9c43c6885b664fa8b60b58db1 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Thu, 29 Jul 2021 14:34:59 -0700
Subject: [PATCH 15/16] Updates invalidation digest output

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 .../backend/experimental/python/lockfile.py   | 13 +++-----
 .../experimental/python/lockfile_metadata.py  | 19 ++++++++++-
 .../python/lockfile_metadata_test.py          | 32 ++++++++++++-------
 3 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile.py b/src/python/pants/backend/experimental/python/lockfile.py
index a3e4c9667d4..45827104fcf 100644
--- a/src/python/pants/backend/experimental/python/lockfile.py
+++ b/src/python/pants/backend/experimental/python/lockfile.py
@@ -3,12 +3,14 @@
 
 from __future__ import annotations
 
-import hashlib
 import logging
 from dataclasses import dataclass
 from typing import cast
 
-from pants.backend.experimental.python.lockfile_metadata import lockfile_content_with_header
+from pants.backend.experimental.python.lockfile_metadata import (
+    invalidation_digest,
+    lockfile_content_with_header,
+)
 from pants.backend.python.subsystems.python_tool_base import (
     PythonToolBase,
     PythonToolRequirementsBase,
@@ -109,12 +111,7 @@ def hex_digest(self) -> str:
 
         Inputs are definted as requirements and interpreter constraints.
         """
-        m = hashlib.sha256()
-        for requirement in self.requirements:
-            m.update(requirement.encode("utf-8"))
-        for constraint in self.interpreter_constraints:
-            m.update(str(constraint).encode("utf-8"))
-        return m.hexdigest()
+        return invalidation_digest(self.requirements, self.interpreter_constraints)
 
 
 @rule(desc="Generate lockfile", level=LogLevel.DEBUG)
diff --git a/src/python/pants/backend/experimental/python/lockfile_metadata.py b/src/python/pants/backend/experimental/python/lockfile_metadata.py
index db37d70ff11..29924f81d4e 100644
--- a/src/python/pants/backend/experimental/python/lockfile_metadata.py
+++ b/src/python/pants/backend/experimental/python/lockfile_metadata.py
@@ -3,8 +3,13 @@
 
 from __future__ import annotations
 
+import hashlib
+import json
 from dataclasses import dataclass
 
+from pants.backend.python.util_rules.interpreter_constraints import InterpreterConstraints
+from pants.util.ordered_set import FrozenOrderedSet
+
 BEGIN_LOCKFILE_HEADER = b"# --- BEGIN PANTS LOCKFILE METADATA: DO NOT EDIT OR REMOVE ---"
 END_LOCKFILE_HEADER = b"# --- END PANTS LOCKFILE METADATA ---"
 
@@ -14,7 +19,19 @@ class LockfileMetadata:
     invalidation_digest: str | None
 
 
-# Lockfile metadata for headers
+def invalidation_digest(
+    requirements: FrozenOrderedSet[str], interpreter_constraints: InterpreterConstraints
+) -> str:
+    """Returns an invalidation digest for the given requirements and interpreter constraints."""
+    m = hashlib.sha256()
+    pres = {
+        "requirements": [str(i) for i in requirements],
+        "interpreter_constraints": [str(i) for i in interpreter_constraints],
+    }
+    m.update(json.dumps(pres).encode("utf-8"))
+    return m.hexdigest()
+
+
 def lockfile_content_with_header(invalidation_digest: str, content: bytes) -> bytes:
     """Returns a version of the lockfile with a pants metadata header prepended."""
     return b"%b\n%b" % (lockfile_metadata_header(invalidation_digest), content)
diff --git a/src/python/pants/backend/experimental/python/lockfile_metadata_test.py b/src/python/pants/backend/experimental/python/lockfile_metadata_test.py
index 1b4dd281be4..3b324989fc8 100644
--- a/src/python/pants/backend/experimental/python/lockfile_metadata_test.py
+++ b/src/python/pants/backend/experimental/python/lockfile_metadata_test.py
@@ -3,8 +3,8 @@
 
 import pytest
 
-from pants.backend.experimental.python.lockfile import PythonLockfileRequest
 from pants.backend.experimental.python.lockfile_metadata import (
+    invalidation_digest,
     lockfile_content_with_header,
     lockfile_metadata_header,
     read_lockfile_metadata,
@@ -46,26 +46,36 @@ def test_validated_lockfile_content() -> None:
 @pytest.mark.parametrize(
     "requirements,interpreter_constraints,expected",
     [
-        ([], [], "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"),
+        ([], [], "51f5289473089f1de64ab760af3f03ff55cd769f25cce7ea82dd1ac88aac5ff4"),
         (
             _interpreter_constraints,
             [],
-            "04a2a2691d10bde0a2320bf32e2d40c60d0db511613fabc71933137c87f61500",
+            "821e8eef80573c7d2460185da4d436b6a8c59e134f5f0758000be3c85e9819eb",
         ),
-        ([], _requirements, "4ffd0a2a29407ce3f6bf7bfca60fdfc6f7d6224adda3c62807eb86666edf93bf"),
+        ([], _requirements, "604fb99ed6d6d83ba2c4eb1230184dd7f279a446cda042e9e87099448f28dddb"),
         (
             _interpreter_constraints,
             _requirements,
-            "6c63e6595f2f6827b6c1b53b186a2fa2020942bbfe989e25059a493b32a8bf36",
+            "9264a3b59a592d7eeac9cb4bbb4f5b2200907694bfe92b48757c99b1f71485f0",
         ),
     ],
 )
 def test_hex_digest(requirements, interpreter_constraints, expected) -> None:
-    req = PythonLockfileRequest(
-        requirements=FrozenOrderedSet(requirements),
-        interpreter_constraints=InterpreterConstraints(interpreter_constraints),
-        dest="lockfile.py",
-        description="empty",
+    print(
+        invalidation_digest(
+            FrozenOrderedSet(requirements), InterpreterConstraints(interpreter_constraints)
+        )
     )
+    assert (
+        invalidation_digest(
+            FrozenOrderedSet(requirements), InterpreterConstraints(interpreter_constraints)
+        )
+        == expected
+    )
+
 
-    assert req.hex_digest == expected
+def test_hash_depends_on_requirement_source():
+    reqs = ["CPython"]
+    assert invalidation_digest(
+        FrozenOrderedSet(reqs), InterpreterConstraints([])
+    ) != invalidation_digest(FrozenOrderedSet([]), InterpreterConstraints(reqs))

From 3694ae3904c5d502340ba6082513f70e8e5f4e84 Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@toolchain.com>
Date: Fri, 30 Jul 2021 08:24:35 -0700
Subject: [PATCH 16/16] Resolve small nitpicks

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]
---
 .../pants/backend/experimental/python/lockfile_metadata.py | 2 +-
 .../backend/experimental/python/lockfile_metadata_test.py  | 7 +------
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/src/python/pants/backend/experimental/python/lockfile_metadata.py b/src/python/pants/backend/experimental/python/lockfile_metadata.py
index 29924f81d4e..cb9e79fe81f 100644
--- a/src/python/pants/backend/experimental/python/lockfile_metadata.py
+++ b/src/python/pants/backend/experimental/python/lockfile_metadata.py
@@ -25,7 +25,7 @@ def invalidation_digest(
     """Returns an invalidation digest for the given requirements and interpreter constraints."""
     m = hashlib.sha256()
     pres = {
-        "requirements": [str(i) for i in requirements],
+        "requirements": list(requirements),
         "interpreter_constraints": [str(i) for i in interpreter_constraints],
     }
     m.update(json.dumps(pres).encode("utf-8"))
diff --git a/src/python/pants/backend/experimental/python/lockfile_metadata_test.py b/src/python/pants/backend/experimental/python/lockfile_metadata_test.py
index 3b324989fc8..582fe0d4279 100644
--- a/src/python/pants/backend/experimental/python/lockfile_metadata_test.py
+++ b/src/python/pants/backend/experimental/python/lockfile_metadata_test.py
@@ -61,11 +61,6 @@ def test_validated_lockfile_content() -> None:
     ],
 )
 def test_hex_digest(requirements, interpreter_constraints, expected) -> None:
-    print(
-        invalidation_digest(
-            FrozenOrderedSet(requirements), InterpreterConstraints(interpreter_constraints)
-        )
-    )
     assert (
         invalidation_digest(
             FrozenOrderedSet(requirements), InterpreterConstraints(interpreter_constraints)
@@ -74,7 +69,7 @@ def test_hex_digest(requirements, interpreter_constraints, expected) -> None:
     )
 
 
-def test_hash_depends_on_requirement_source():
+def test_hash_depends_on_requirement_source() -> None:
     reqs = ["CPython"]
     assert invalidation_digest(
         FrozenOrderedSet(reqs), InterpreterConstraints([])