Shorten object file path

Closes #4781.
Fix https://github.com/bazelbuild/bazel/issues/4149

RELNOTES:
Users can now pass --experimental_shortened_obj_file_path=true to have a shorter object file path, the object file paths (and all other related paths) will be constructed as following:
If there's no two or more source files with the same base name:
  <bazel-bin>/<target_package_path>/_objs/<target_name>/<source_base_name>.<extension>
otherwise:
  <bazel-bin>/<target_package_path>/_objs/<target_name>/N/<source_base_name>.<extension>
  N = the file?s order among the source files with the same basename, starts from 0.

Examples:
1. Output names for ["lib1/foo.cc", "lib2/bar.cc"] are ["foo", "bar"]
2. Output names for ["foo.cc", "bar.cc", "foo.cpp", "lib/foo.cc"] are
   ["0/foo", "bar", "1/foo", "2/foo"]

The default value of --experimental_shortened_obj_file_path option is false, but we plan to flip it to true and eventually remove this option.
You shouldn't depend on the format of generated object file path, but if you do and this change breaks you, please use --experimental_shortened_obj_file_path=false to work around it.

PiperOrigin-RevId: 190214375

1 files changed, 52 insertions, 0 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcLibraryTest.java b/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcLibraryTest.java
index 8bb93d66f8..8226bc1bc8 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcLibraryTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/objc/ObjcLibraryTest.java
@@ -123,6 +123,58 @@ public class ObjcLibraryTest extends ObjcRuleTestCase {
   }
 
   @Test
+  public void testCompilesSourcesWithSameBaseNameWithNewObjPath() throws Exception {
+    useConfiguration("--experimental_shortened_obj_file_path=true");
+    createLibraryTargetWriter("//foo:lib")
+        .setAndCreateFiles("srcs", "a.m", "pkg1/a.m", "b.m")
+        .setAndCreateFiles("non_arc_srcs", "pkg2/a.m")
+        .write();
+
+    getConfiguredTarget("//foo:lib");
+
+    Artifact a0 = getBinArtifact("_objs/lib/arc/0/a.o", "//foo:lib");
+    Artifact a1 = getBinArtifact("_objs/lib/arc/1/a.o", "//foo:lib");
+    Artifact a2 = getBinArtifact("_objs/lib/non_arc/a.o", "//foo:lib");
+    Artifact b = getBinArtifact("_objs/lib/arc/b.o", "//foo:lib");
+
+    assertThat(getGeneratingAction(a0)).isNotNull();
+    assertThat(getGeneratingAction(a1)).isNotNull();
+    assertThat(getGeneratingAction(a2)).isNotNull();
+    assertThat(getGeneratingAction(b)).isNotNull();
+
+    assertThat(getGeneratingAction(a0).getInputs()).contains(getSourceArtifact("foo/a.m"));
+    assertThat(getGeneratingAction(a1).getInputs()).contains(getSourceArtifact("foo/pkg1/a.m"));
+    assertThat(getGeneratingAction(a2).getInputs()).contains(getSourceArtifact("foo/pkg2/a.m"));
+    assertThat(getGeneratingAction(b).getInputs()).contains(getSourceArtifact("foo/b.m"));
+  }
+
+  @Test
+  public void testCompilesSourcesWithSameBaseNameWithLegacyObjPath() throws Exception {
+    useConfiguration("--experimental_shortened_obj_file_path=false");
+    createLibraryTargetWriter("//foo:lib")
+        .setAndCreateFiles("srcs", "a.m", "pkg1/a.m", "b.m")
+        .setAndCreateFiles("non_arc_srcs", "pkg2/a.m")
+        .write();
+
+    getConfiguredTarget("//foo:lib");
+
+    Artifact a0 = getBinArtifact("_objs/lib/foo/a.o", "//foo:lib");
+    Artifact a1 = getBinArtifact("_objs/lib/foo/pkg1/a.o", "//foo:lib");
+    Artifact a2 = getBinArtifact("_objs/lib/foo/pkg2/a.o", "//foo:lib");
+    Artifact b = getBinArtifact("_objs/lib/foo/b.o", "//foo:lib");
+
+    assertThat(getGeneratingAction(a0)).isNotNull();
+    assertThat(getGeneratingAction(a1)).isNotNull();
+    assertThat(getGeneratingAction(a2)).isNotNull();
+    assertThat(getGeneratingAction(b)).isNotNull();
+
+    assertThat(getGeneratingAction(a0).getInputs()).contains(getSourceArtifact("foo/a.m"));
+    assertThat(getGeneratingAction(a1).getInputs()).contains(getSourceArtifact("foo/pkg1/a.m"));
+    assertThat(getGeneratingAction(a2).getInputs()).contains(getSourceArtifact("foo/pkg2/a.m"));
+    assertThat(getGeneratingAction(b).getInputs()).contains(getSourceArtifact("foo/b.m"));
+  }
+
+  @Test
   public void testObjcPlusPlusCompile() throws Exception {
     useConfiguration(
         "--cpu=ios_i386",