C++: Adds tests for transitive link and fixes bugs

Bugs fixed:
 - Creating static libraries during transitive link
 - Could not return None from linking_outputs' executable or library_to_link
 - Null pointer exception when not passing compilation_outputs to link()

#4570

RELNOTES:none
PiperOrigin-RevId: 245956660

src/main/java/com/google/devtools/build/lib/bazel/rules/cpp/BazelCcModule.java

@@ -110,7 +110,7 @@ public CcLinkingOutputs link(
       SkylarkActionFactory actions,
       FeatureConfigurationForStarlark skylarkFeatureConfiguration,
       CcToolchainProvider skylarkCcToolchainProvider,
-      CcCompilationOutputs compilationOutputs,
+      Object compilationOutputs,
       SkylarkList<String> userLinkFlags,
       SkylarkList<CcLinkingContext> linkingContexts,
       String name,
@@ -126,7 +126,7 @@ public CcLinkingOutputs link(
         actions,
         skylarkFeatureConfiguration,
         skylarkCcToolchainProvider,
-        compilationOutputs,
+        convertFromNoneable(compilationOutputs, /* defaultValue= */ null),
         userLinkFlags,
         linkingContexts,
         name,

src/main/java/com/google/devtools/build/lib/rules/cpp/CcModule.java

@@ -1595,7 +1595,6 @@ protected CcLinkingOutputs link(
       throw new EvalException(
           location, "Language '" + language + "' does not support " + outputType);
     }
-
     CcLinkingHelper helper =
         new CcLinkingHelper(
                 actions.getActionConstructionContext().getRuleErrorConsumer(),
@@ -1617,13 +1616,11 @@ protected CcLinkingOutputs link(
             .addNonCodeLinkerInputs(additionalInputs)
             .setDynamicLinkType(dynamicLinkTargetType)
             .addCcLinkingContexts(linkingContexts)
+            .setShouldCreateStaticLibraries(false)
             .addLinkopts(userLinkFlags);
     try {
-      CcLinkingOutputs ccLinkingOutputs = CcLinkingOutputs.EMPTY;
-      if (!compilationOutputs.isEmpty()) {
-        ccLinkingOutputs = helper.link(compilationOutputs);
-      }
-      return ccLinkingOutputs;
+      return helper.link(
+          compilationOutputs != null ? compilationOutputs : CcCompilationOutputs.EMPTY);
     } catch (RuleErrorException e) {
       throw new EvalException(location, e);
     }

src/main/java/com/google/devtools/build/lib/skylarkbuildapi/cpp/BazelCcModuleApi.java

@@ -240,7 +240,10 @@ Tuple<Object> compile(
             named = true,
             defaultValue = "None",
             noneable = true,
-            type = CcCompilationOutputsApi.class),
+            allowedTypes = {
+              @ParamType(type = CcCompilationOutputsApi.class),
+              @ParamType(type = NoneType.class)
+            }),
         @Param(
             name = "user_link_flags",
             doc = "Additional list of linker options.",
@@ -303,7 +306,7 @@ LinkingOutputsT link(
       SkylarkActionFactoryT skylarkActionFactoryApi,
       FeatureConfigurationT skylarkFeatureConfiguration,
       CcToolchainProviderT skylarkCcToolchainProvider,
-      CompilationOutputsT compilationOutputs,
+      Object compilationOutputs,
       SkylarkList<String> userLinkFlags,
       SkylarkList<LinkingContextT> linkingContexts,
       String name,

src/main/java/com/google/devtools/build/lib/skylarkbuildapi/cpp/CcLinkingOutputsApi.java

@@ -26,9 +26,17 @@
     documented = false,
     doc = "Helper class containing CC compilation outputs.")
 public interface CcLinkingOutputsApi<FileT extends FileApi> {
-  @SkylarkCallable(name = "library_to_link", structField = true, documented = false)
+  @SkylarkCallable(
+      name = "library_to_link",
+      structField = true,
+      allowReturnNones = true,
+      documented = false)
   LibraryToLinkApi<FileT> getLibraryToLink();
 
-  @SkylarkCallable(name = "executable", structField = true, documented = false)
+  @SkylarkCallable(
+      name = "executable",
+      structField = true,
+      allowReturnNones = true,
+      documented = false)
   FileT getExecutable();
 }

src/main/java/com/google/devtools/build/skydoc/fakebuildapi/cpp/FakeCcModule.java

@@ -219,7 +219,7 @@ public CcLinkingOutputsApi<FileApi> link(
       SkylarkActionFactoryApi skylarkActionFactoryApi,
       FeatureConfigurationApi skylarkFeatureConfiguration,
       CcToolchainProviderApi<FeatureConfigurationApi> skylarkCcToolchainProvider,
-      CcCompilationOutputsApi<FileApi> compilationOutputs,
+      Object compilationOutputs,
       SkylarkList<String> userLinkFlags,
       SkylarkList<CcLinkingContextApi<FileApi>> linkingContexts,
       String name,

src/test/java/com/google/devtools/build/lib/rules/cpp/SkylarkCcCommonTest.java

@@ -50,6 +50,7 @@
 import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.WithFeatureSet;
 import com.google.devtools.build.lib.rules.cpp.CcToolchainVariables.StringValueParser;
 import com.google.devtools.build.lib.syntax.EvalException;
+import com.google.devtools.build.lib.syntax.EvalUtils;
 import com.google.devtools.build.lib.syntax.SkylarkDict;
 import com.google.devtools.build.lib.syntax.SkylarkList;
 import com.google.devtools.build.lib.syntax.SkylarkNestedSet;
@@ -5211,4 +5212,113 @@ private void setupCcOutputsTest() throws Exception {
         "    },",
         ")");
   }
+
+  @Test
+  public void testTransitiveLinkWithDeps() throws Exception {
+    setupTestTransitiveLink(scratch, "        linking_contexts = dep_linking_contexts");
+    ConfiguredTarget target = getConfiguredTarget("//foo:bin");
+    assertThat(target).isNotNull();
+    Artifact executable = (Artifact) getMyInfoFromTarget(target).getValue("executable");
+    assertThat(artifactsToStrings(getGeneratingAction(executable).getInputs()))
+        .containsAllOf("bin foo/libdep1.a", "bin foo/libdep2.a");
+  }
+
+  @Test
+  public void testTransitiveLinkForDynamicLibrary() throws Exception {
+    setupTestTransitiveLink(scratch, "output_type = 'dynamic_library'");
+    ConfiguredTarget target = getConfiguredTarget("//foo:bin");
+    assertThat(target).isNotNull();
+    LibraryToLink library = (LibraryToLink) getMyInfoFromTarget(target).getValue("library");
+    assertThat(library).isNotNull();
+    Object executable = getMyInfoFromTarget(target).getValue("executable");
+    assertThat(EvalUtils.isNullOrNone(executable)).isTrue();
+  }
+
+  @Test
+  public void testTransitiveLinkForExecutable() throws Exception {
+    setupTestTransitiveLink(scratch, "output_type = 'executable'");
+    ConfiguredTarget target = getConfiguredTarget("//foo:bin");
+    assertThat(target).isNotNull();
+    Artifact executable = (Artifact) getMyInfoFromTarget(target).getValue("executable");
+    assertThat(executable).isNotNull();
+    Object library = getMyInfoFromTarget(target).getValue("library");
+    assertThat(EvalUtils.isNullOrNone(library)).isTrue();
+  }
+
+  @Test
+  public void testTransitiveLinkWithCompilationOutputs() throws Exception {
+    setupTestTransitiveLink(scratch, "compilation_outputs=objects");
+    ConfiguredTarget target = getConfiguredTarget("//foo:bin");
+    assertThat(target).isNotNull();
+    Artifact executable = (Artifact) getMyInfoFromTarget(target).getValue("executable");
+    assertThat(artifactsToStrings(getGeneratingAction(executable).getInputs()))
+        .contains("src foo/file.o");
+  }
+
+  private static void setupTestTransitiveLink(Scratch scratch, String... additionalLines)
+      throws Exception {
+    String fragments = "    fragments = ['google_cpp', 'cpp'],";
+    if (AnalysisMock.get().isThisBazel()) {
+      fragments = "    fragments = ['cpp'],";
+    }
+    scratch.overwriteFile("tools/build_defs/BUILD");
+    scratch.file(
+        "tools/build_defs/extension.bzl",
+        "load('//myinfo:myinfo.bzl', 'MyInfo')",
+        "def _cc_bin_impl(ctx):",
+        "    toolchain = ctx.attr._cc_toolchain[cc_common.CcToolchainInfo]",
+        "    feature_configuration = cc_common.configure_features(cc_toolchain = toolchain)",
+        "    dep_linking_contexts = []",
+        "    for dep in ctx.attr.deps:",
+        "        dep_linking_contexts.append(dep[CcInfo].linking_context)",
+        "    objects = cc_common.create_compilation_outputs(objects=depset(ctx.files.objects),",
+        "        pic_objects=depset(ctx.files.pic_objects))",
+        "    linking_outputs = cc_common.link(",
+        "        actions=ctx.actions,",
+        "        feature_configuration=feature_configuration,",
+        "        name = ctx.label.name,",
+        "        cc_toolchain=toolchain,",
+        "        " + Joiner.on("").join(additionalLines),
+        "    )",
+        "    return [",
+        "      MyInfo(",
+        "        library=linking_outputs.library_to_link,",
+        "        executable=linking_outputs.executable",
+        "      )",
+        "    ]",
+        "cc_bin = rule(",
+        "    implementation = _cc_bin_impl,",
+        "    attrs = {",
+        "      'objects': attr.label_list(allow_files=True),",
+        "      'pic_objects': attr.label_list(allow_files=True),",
+        "      'deps': attr.label_list(),",
+        "      '_cc_toolchain': attr.label(default =",
+        "          configuration_field(fragment = 'cpp', name = 'cc_toolchain'))",
+        "    },",
+        fragments,
+        ")");
+    scratch.file(
+        "foo/BUILD",
+        "load('//tools/build_defs:extension.bzl', 'cc_bin')",
+        "cc_library(",
+        "    name = 'dep1',",
+        "    srcs = ['dep1.cc'],",
+        "    hdrs = ['dep1.h'],",
+        "    includes = ['dep1/baz'],",
+        "    defines = ['DEP1'],",
+        ")",
+        "cc_library(",
+        "    name = 'dep2',",
+        "    srcs = ['dep2.cc'],",
+        "    hdrs = ['dep2.h'],",
+        "    includes = ['dep2/qux'],",
+        "    defines = ['DEP2'],",
+        ")",
+        "cc_bin(",
+        "    name = 'bin',",
+        "    objects = ['file.o'],",
+        "    pic_objects = ['file.pic.o'],",
+        "    deps = [':dep1', ':dep2'],",
+        ")");
+  }
 }