Add emit_extension_block_symbols for symbol graph extraction

The `emit_extension_block_symbols` attr can be used in the `swift_extract_symbol_graph` rule to pass the `-emit-extension-block-symbols` flag when creating the symbol graphs. This enables generating symbol graph information for extensions of custom types.

doc/api.md

@@ -538,9 +538,9 @@ The module name derived from the label.
 ## swift_common.extract_symbol_graph
 
 <pre>
-swift_common.extract_symbol_graph(<a href="#swift_common.extract_symbol_graph-actions">actions</a>, <a href="#swift_common.extract_symbol_graph-compilation_contexts">compilation_contexts</a>, <a href="#swift_common.extract_symbol_graph-feature_configuration">feature_configuration</a>,
-                                  <a href="#swift_common.extract_symbol_graph-include_dev_srch_paths">include_dev_srch_paths</a>, <a href="#swift_common.extract_symbol_graph-minimum_access_level">minimum_access_level</a>, <a href="#swift_common.extract_symbol_graph-module_name">module_name</a>,
-                                  <a href="#swift_common.extract_symbol_graph-output_dir">output_dir</a>, <a href="#swift_common.extract_symbol_graph-swift_infos">swift_infos</a>, <a href="#swift_common.extract_symbol_graph-swift_toolchain">swift_toolchain</a>)
+swift_common.extract_symbol_graph(<a href="#swift_common.extract_symbol_graph-actions">actions</a>, <a href="#swift_common.extract_symbol_graph-compilation_contexts">compilation_contexts</a>, <a href="#swift_common.extract_symbol_graph-emit_extension_block_symbols">emit_extension_block_symbols</a>,
+                                  <a href="#swift_common.extract_symbol_graph-feature_configuration">feature_configuration</a>, <a href="#swift_common.extract_symbol_graph-include_dev_srch_paths">include_dev_srch_paths</a>, <a href="#swift_common.extract_symbol_graph-minimum_access_level">minimum_access_level</a>,
+                                  <a href="#swift_common.extract_symbol_graph-module_name">module_name</a>, <a href="#swift_common.extract_symbol_graph-output_dir">output_dir</a>, <a href="#swift_common.extract_symbol_graph-swift_infos">swift_infos</a>, <a href="#swift_common.extract_symbol_graph-swift_toolchain">swift_toolchain</a>)
 </pre>
 
 Extracts the symbol graph from a Swift module.
@@ -552,6 +552,7 @@ Extracts the symbol graph from a Swift module.
 | :------------- | :------------- | :------------- |
 | <a id="swift_common.extract_symbol_graph-actions"></a>actions |  The object used to register actions.   |  none |
 | <a id="swift_common.extract_symbol_graph-compilation_contexts"></a>compilation_contexts |  A list of `CcCompilationContext`s that represent C/Objective-C requirements of the target being compiled, such as Swift-compatible preprocessor defines, header search paths, and so forth. These are typically retrieved from the `CcInfo` providers of a target's dependencies.   |  none |
+| <a id="swift_common.extract_symbol_graph-emit_extension_block_symbols"></a>emit_extension_block_symbols |  A `bool` that indicates whether `extension` block information should be included in the symbol graph.   |  `None` |
 | <a id="swift_common.extract_symbol_graph-feature_configuration"></a>feature_configuration |  The Swift feature configuration.   |  none |
 | <a id="swift_common.extract_symbol_graph-include_dev_srch_paths"></a>include_dev_srch_paths |  A `bool` that indicates whether the developer framework search paths will be added to the compilation command.   |  none |
 | <a id="swift_common.extract_symbol_graph-minimum_access_level"></a>minimum_access_level |  The minimum access level of the declarations that should be extracted into the symbol graphs. The default value is `None`, which means the Swift compiler's default behavior should be used (at the time of this writing, the default behavior is "public").   |  `None` |

swift/internal/swift_symbol_graph_aspect.bzl

@@ -49,6 +49,7 @@ def _swift_symbol_graph_aspect_impl(target, aspect_ctx):
         else:
             compilation_context = cc_common.create_compilation_context()
 
+        emit_extension_block_symbols = aspect_ctx.attr.emit_extension_block_symbols
         minimum_access_level = aspect_ctx.attr.minimum_access_level
 
         for module in swift_info.direct_modules:
@@ -59,6 +60,7 @@ def _swift_symbol_graph_aspect_impl(target, aspect_ctx):
             extract_symbol_graph(
                 actions = aspect_ctx.actions,
                 compilation_contexts = [compilation_context],
+                emit_extension_block_symbols = emit_extension_block_symbols,
                 feature_configuration = feature_configuration,
                 include_dev_srch_paths = include_developer_search_paths(
                     aspect_ctx.rule.attr,
@@ -113,12 +115,16 @@ def _testonly_symbol_graph_aspect_impl(target, aspect_ctx):
 
 def make_swift_symbol_graph_aspect(
         *,
+        default_emit_extension_block_symbols,
         default_minimum_access_level,
         doc = "",
         testonly_targets):
     """Creates an aspect that extracts Swift symbol graphs from dependencies.
 
     Args:
+        default_emit_extension_block_symbols: The default value for the `emit_extension_block_symbols`
+            attribute of the aspect. A rule that applies this aspect can let users
+            override this value if it also provides an attribute named `emit_extension_block_symbols`.
         default_minimum_access_level: The default minimum access level of the
             declarations that should be emitted in the symbol graphs. A rule
             that applies this aspect can let users override this value if it
@@ -140,6 +146,24 @@ def make_swift_symbol_graph_aspect(
         attrs = dicts.add(
             swift_toolchain_attrs(),
             {
+                # TODO: use `attr.bool` once https://github.com/bazelbuild/bazel/issues/22809 is resolved.
+                "emit_extension_block_symbols": attr.string(
+                    default = default_emit_extension_block_symbols,
+                    doc = """\
+Defines if the symbol graph information for `extension` blocks should be
+emitted in addition to the default symbol graph information.
+
+This value must be either `"0"` or `"1"`.When the value is `"1"`, the symbol
+graph information for `extension` blocks will be emitted in addition to
+the default symbol graph information. The default value is `"{default_value}"`.
+""".format(
+                        default_value = default_emit_extension_block_symbols,
+                    ),
+                    values = [
+                        "0",
+                        "1",
+                    ],
+                ),
                 "minimum_access_level": attr.string(
                     default = default_minimum_access_level,
                     doc = """\

swift/internal/symbol_graph_extracting.bzl

@@ -30,6 +30,12 @@ def symbol_graph_action_configs():
         The list of action configs needed to extract symbol graphs.
     """
     return [
+        swift_toolchain_config.action_config(
+            actions = [swift_action_names.SYMBOL_GRAPH_EXTRACT],
+            configurators = [
+                _symbol_graph_emit_extension_block_symbols_configurator,
+            ],
+        ),
         swift_toolchain_config.action_config(
             actions = [swift_action_names.SYMBOL_GRAPH_EXTRACT],
             configurators = [
@@ -44,6 +50,13 @@ def symbol_graph_action_configs():
         ),
     ]
 
+def _symbol_graph_emit_extension_block_symbols_configurator(prerequisites, args):
+    """Configures whether `extension` block information should be emitted in the symbol graph."""
+
+    # TODO: update to use `bool` once https://github.com/bazelbuild/bazel/issues/22809 is resolved.
+    if prerequisites.emit_extension_block_symbols == "1":
+        args.add("-emit-extension-block-symbols")
+
 def _symbol_graph_minimum_access_level_configurator(prerequisites, args):
     """Configures the minimum access level of the symbol graph extraction."""
     if prerequisites.minimum_access_level:
@@ -57,6 +70,7 @@ def extract_symbol_graph(
         *,
         actions,
         compilation_contexts,
+        emit_extension_block_symbols = None,
         feature_configuration,
         include_dev_srch_paths,
         minimum_access_level = None,
@@ -73,6 +87,8 @@ def extract_symbol_graph(
             Swift-compatible preprocessor defines, header search paths, and so
             forth. These are typically retrieved from the `CcInfo` providers of
             a target's dependencies.
+        emit_extension_block_symbols: A `bool` that indicates whether `extension` block
+            information should be included in the symbol graph.
         feature_configuration: The Swift feature configuration.
         include_dev_srch_paths: A `bool` that indicates whether the developer
             framework search paths will be added to the compilation command.
@@ -121,6 +137,7 @@ def extract_symbol_graph(
         bin_dir = feature_configuration._bin_dir,
         cc_compilation_context = merged_compilation_context,
         developer_dirs = swift_toolchain.developer_dirs,
+        emit_extension_block_symbols = emit_extension_block_symbols,
         genfiles_dir = feature_configuration._genfiles_dir,
         include_dev_srch_paths = include_dev_srch_paths,
         is_swift = True,

swift/swift_extract_symbol_graph.bzl

@@ -72,6 +72,22 @@ done
 
 swift_extract_symbol_graph = rule(
     attrs = {
+        # TODO: use `attr.bool` once https://github.com/bazelbuild/bazel/issues/22809 is resolved.
+        "emit_extension_block_symbols": attr.string(
+            default = "0",
+            doc = """\
+Defines if the symbol graph information for `extension` blocks should be
+emitted in addition to the default symbol graph information.
+
+This value must be either `"0"` or `"1"`.When the value is `"1"`, the symbol
+graph information for `extension` blocks will be emitted in addition to
+the default symbol graph information. The default value is `"0"`.
+""",
+            values = [
+                "0",
+                "1",
+            ],
+        ),
         "minimum_access_level": attr.string(
             default = "public",
             doc = """\

swift/swift_symbol_graph_aspect.bzl

@@ -20,6 +20,7 @@ load(
 )
 
 swift_symbol_graph_aspect = make_swift_symbol_graph_aspect(
+    default_emit_extension_block_symbols = "0",
     default_minimum_access_level = "public",
     doc = """\
 Extracts symbol graphs from Swift modules in the build graph.

swift/swift_test.bzl

@@ -51,6 +51,7 @@ load(
 load(":swift_common.bzl", "swift_common")
 
 _test_discovery_symbol_graph_aspect = make_swift_symbol_graph_aspect(
+    default_emit_extension_block_symbols = "0",
     default_minimum_access_level = "internal",
     testonly_targets = True,
 )

test/fixtures/symbol_graphs/BUILD

@@ -22,6 +22,13 @@ swift_library(
     tags = FIXTURE_TAGS,
 )
 
+swift_library(
+    name = "some_module_with_extension",
+    srcs = ["SomeModuleWithExtension.swift"],
+    module_name = "SomeModuleWithExtension",
+    tags = FIXTURE_TAGS,
+)
+
 swift_library(
     name = "importing_module",
     srcs = ["ImportingModule.swift"],
@@ -36,6 +43,13 @@ swift_extract_symbol_graph(
     targets = [":some_module"],
 )
 
+swift_extract_symbol_graph(
+    name = "some_module_symbol_graph_with_extension_block_symbols",
+    emit_extension_block_symbols = "1",
+    tags = FIXTURE_TAGS,
+    targets = [":some_module_with_extension"],
+)
+
 swift_extract_symbol_graph(
     name = "importing_module_symbol_graph",
     tags = FIXTURE_TAGS,

test/fixtures/symbol_graphs/SomeModuleWithExtension.swift

@@ -0,0 +1,19 @@
+/// This class is documented.
+public class SomeClass {
+  /// This method is documented.
+  ///
+  /// - Parameter count: This parameter is documented.
+  /// - Returns: This return value is documented.
+  public func someMethod(someParameter count: Int) -> String {
+    return String(repeating: "someString", count: count)
+  }
+}
+
+extension SomeClass {
+  /// This method is documented, and it's on an extension of a custom type.
+  ///
+  /// - Returns: This return value is documented.
+  public func someExtensionMethod() -> String {
+    return "someString"
+  }
+}

test/symbol_graphs_tests.bzl

@@ -41,6 +41,27 @@ def symbol_graphs_test_suite(name):
         target_under_test = "@build_bazel_rules_swift//test/fixtures/symbol_graphs:some_module_symbol_graph",
     )
 
+    # TODO: ideally this tests the contents of the json file(s) to ensure
+    # the extension block symbols are present, but requires a json content test which
+    # is not yet implemented.
+    #
+    # Verify that the `swift_extract_symbol_graph` rule produces a directory
+    # output containing the correct files when the rule additionally requests
+    # to emit extension block symbols.
+    directory_test(
+        name = "{}_extract_rule_outputs_extension_block_symbols_files".format(name),
+        expected_directories = {
+            "test/fixtures/symbol_graphs/some_module_symbol_graph_with_extension_block_symbols.symbolgraphs": [
+                "SomeModuleWithExtension.symbols.json",
+            ],
+        },
+        tags = [name],
+        target_under_test = "@build_bazel_rules_swift//test/fixtures/symbol_graphs:some_module_symbol_graph_with_extension_block_symbols",
+        # TODO: remove this constraint once Swift version in CI for Linux/Windows is updated to 5.9+
+        # until then `-emit-extension-block-symbols` is not testable as the compiler does not have the flag.
+        target_compatible_with = ["@platforms//os:macos"],
+    )
+
     # Verify that the `swift_extract_symbol_graph` rule produces a directory
     # output containing only the graph for the requested target and not its
     # dependencies.