NuGet resolution fixes (#366)

## What?
* Fix resolution in packages that have disjoint lib and ref folders.
* Make `nuget_repo` take in a map of TFM to deps so that the dependency graph for each TFM is more accurate
* Update paket2bazel so that it generates correct deps per TFM

dotnet/private/rules/nuget/nuget_archive.bzl

@@ -360,13 +360,25 @@ def _nuget_archive_impl(ctx):
 
         _process_key_and_file(groups, key, file)
 
-    # in some runtime specific edge cases there exist certain tfm refs but the libs are not shipped
     if groups.get("ref") and groups.get("lib"):
         libs = groups.get("lib")
+        refs = groups.get("ref")
+
+        # in some runtime specific edge cases there exist certain tfm refs but the libs are not shipped
         for (tfm, _) in groups.get("ref").items():
             if tfm not in libs:
                 libs[tfm] = []
 
+        # We add an empty entry for each tfm that does not exist in the refs
+        # because that way the generated select statement will contain all the
+        # supported tfms and thus we can omit an default case in the select which
+        # would make the build graph more fragile and harder to debug since instead
+        # of Bazel complaining that a some tfm is not supported for a package you would
+        # possibly get an error during compilation
+        for (tfm, _) in groups.get("lib").items():
+            if tfm not in refs:
+                refs[tfm] = []
+
     ctx.file("BUILD.bazel", r"""package(default_visibility = ["//visibility:public"])
 exports_files(glob(["**"]))
 load("@rules_dotnet//dotnet/private/rules/nuget:nuget_archive.bzl", "tfm_filegroup", "rid_filegroup")

dotnet/private/rules/nuget/nuget_repo.bzl

@@ -6,8 +6,18 @@ load("@rules_dotnet//dotnet/private/rules/nuget:nuget_archive.bzl", "nuget_archi
 _GLOBAL_NUGET_PREFIX = "nuget"
 
 def _nuget_repo_impl(ctx):
-    for (name_version, deps) in ctx.attr.packages.items():
-        [name, version, sha512] = name_version.split("|")
+    for package in ctx.attr.packages:
+        package = json.decode(package)
+        name = package["id"]
+        version = package["version"]
+        sha512 = package["sha512"]
+        deps = package["dependencies"]
+
+        # deps = []
+        # for (tfm, tfm_deps) in dependencies.items():
+        #     for dep in tfm_deps:
+        #         if dep not in deps:
+        #             deps.append(dep)
 
         targeting_pack_overrides = ctx.attr.targeting_pack_overrides[name.lower()]
         template = Label("@rules_dotnet//dotnet/private/rules/nuget:template.BUILD")
@@ -17,7 +27,7 @@ def _nuget_repo_impl(ctx):
             "{NAME}": name,
             "{NAME_LOWER}": name.lower(),
             "{VERSION}": version,
-            "{DEPS}": ",".join(["\n    \"@{}//{}\"".format(ctx.name.lower(), d.lower()) for d in deps]),
+            "{DEPS}": ",".join(["\n    \"@rules_dotnet//dotnet:tfm_{tfm}\": [{deps_list}]".format(tfm = tfm, deps_list = ",".join(["\"@{nuget_repo_name}//{dep_name}\"".format(dep_name = d.lower(), nuget_repo_name = ctx.name.lower()) for d in tfm_deps])) for (tfm, tfm_deps) in deps.items()]),
             "{TARGETING_PACK_OVERRIDES}": json.encode({override.lower().split("|")[0]: override.lower().split("|")[1] for override in targeting_pack_overrides}),
             "{SHA_512}": sha512,
         })
@@ -31,7 +41,7 @@ alias(name = "content_files", actual = "@{prefix}.{name}.v{version}//:content_fi
 _nuget_repo = repository_rule(
     _nuget_repo_impl,
     attrs = {
-        "packages": attr.string_list_dict(
+        "packages": attr.string_list(
             mandatory = True,
             allow_empty = False,
         ),
@@ -46,24 +56,24 @@ _nuget_repo = repository_rule(
 def nuget_repo(name, packages):
     # TODO: Add docs
     # scaffold individual nuget archives
-    for (package_name, version, sha512, sources, netrc, _deps, _targeting_pack_overrides) in packages:
-        package_name = package_name.lower()
-        version = version.lower()
+    for package in packages:
+        package_name = package["id"].lower()
+        version = package["version"].lower()
 
         # maybe another nuget_repo has the same nuget package dependency
         maybe(
             nuget_archive,
             name = "{}.{}.v{}".format(_GLOBAL_NUGET_PREFIX, package_name, version),
-            sources = sources,
-            netrc = netrc,
+            sources = package["sources"],
+            netrc = package.get("netrc", None),
             id = package_name,
             version = version,
-            sha512 = sha512,
+            sha512 = package["sha512"],
         )
 
     # scaffold transitive @name// dependency tree
     _nuget_repo(
         name = name,
-        packages = {"{}|{}|{}".format(name, version, sha512): deps for (name, version, sha512, _sources, _netrc, deps, _) in packages},
-        targeting_pack_overrides = {"{}".format(name.lower()): targeting_pack_overrides for (name, _, _, _, _, _, targeting_pack_overrides) in packages},
+        packages = [json.encode(package) for package in packages],
+        targeting_pack_overrides = {"{}".format(package["id"].lower()): package["targeting_pack_overrides"] for package in packages},
     )

dotnet/private/rules/nuget/template.BUILD

@@ -13,5 +13,7 @@ import_library(
     sha512 = "{SHA_512}",
     targeting_pack_overrides = {TARGETING_PACK_OVERRIDES},
     version = "{VERSION}",
-    deps = [{DEPS}],
+    deps = select({
+        {DEPS},
+    }),
 )

dotnet/private/tests/nuget_structure/BUILD.bazel

@@ -1,11 +1,14 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
 load(":runtimes.bzl", "runtimes_structure")
 load(":typeproviders.bzl", "typeproviders_structure")
+load(":resolution.bzl", "resolution_structure")
 
 typeproviders_structure()
 
 runtimes_structure()
 
+resolution_structure()
+
 bzl_library(
     name = "common",
     srcs = ["common.bzl"],

dotnet/private/tests/nuget_structure/resolution.bzl

@@ -0,0 +1,20 @@
+"NuGet structure tests"
+
+load("//dotnet/private/tests/nuget_structure:common.bzl", "nuget_structure_test", "nuget_test_wrapper")
+
+# buildifier: disable=unnamed-macro
+def resolution_structure():
+    "Tests for the resolution of files depending on target framework"
+    nuget_test_wrapper(
+        name = "System.Memory.netstandard2.0",
+        target_framework = "netstandard2.0",
+        runtime_identifier = "linux-x64",
+        package = "@rules_dotnet_dev_nuget_packages//system.memory",
+    )
+
+    nuget_structure_test(
+        name = "should_resolve_system.memory_netstandard2.0_linux-x64_correctly",
+        target_under_test = ":System.Memory.netstandard2.0",
+        expected_libs = ["lib/netstandard2.0/System.Memory.dll"],
+        expected_refs = [],
+    )