C++ libraries in remote repos don't need to set include paths

Fixes #445, based on https://github.com/bazelbuild/bazel/compare/master...ulfjack:cpp-include-path.

RELNOTES: C++ libraries no longer need includes = ["."] (or similar copts) to include paths relative to a remote repository's root.

--
MOS_MIGRATED_REVID=107593486

3 files changed, 55 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java
index 0b5fb442cd..cce02514eb 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java
@@ -743,8 +743,11 @@ public final class CcLibraryHelper {
     // generated files. It is important that the execRoot (EMPTY_FRAGMENT) comes
     // before the genfilesFragment to preferably pick up source files. Otherwise
     // we might pick up stale generated files.
-    contextBuilder.addQuoteIncludeDir(PathFragment.EMPTY_FRAGMENT);
-    contextBuilder.addQuoteIncludeDir(ruleContext.getConfiguration().getGenfilesFragment());
+    PathFragment repositoryPath =
+        ruleContext.getLabel().getPackageIdentifier().getRepository().getPathFragment();
+    contextBuilder.addQuoteIncludeDir(repositoryPath);
+    contextBuilder.addQuoteIncludeDir(
+        ruleContext.getConfiguration().getGenfilesFragment().getRelative(repositoryPath));
 
     for (PathFragment systemIncludeDir : systemIncludeDirs) {
       contextBuilder.addSystemIncludeDir(systemIncludeDir);
diff --git a/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java b/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java
index 434cdcfc2c..97221abf6f 100644
--- a/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java
+++ b/src/main/java/com/google/devtools/build/lib/vfs/PathFragment.java
@@ -379,6 +379,9 @@ public final class PathFragment implements Comparable<PathFragment>, Serializabl
    * with no path normalization or I/O performed.
    */
   public PathFragment getRelative(PathFragment otherFragment) {
+    if (otherFragment == EMPTY_FRAGMENT) {
+      return this;
+    }
     return otherFragment.isAbsolute()
         ? otherFragment
         : new PathFragment(this, otherFragment);
diff --git a/src/test/shell/bazel/local_repository_test.sh b/src/test/shell/bazel/local_repository_test.sh
index c0c8cb5de0..8506569d34 100755
--- a/src/test/shell/bazel/local_repository_test.sh
+++ b/src/test/shell/bazel/local_repository_test.sh
@@ -924,4 +924,51 @@ EOF
   expect_log "workspace names may contain only A-Z, a-z, 0-9, '-', '_' and '.'"
 }
 
+function test_remote_includes() {
+  local remote=$TEST_TMPDIR/r
+  rm -fr $remote
+  mkdir -p $remote/inc
+
+  touch $remote/WORKSPACE
+  cat > $remote/BUILD <<EOF
+cc_library(
+    name = "bar",
+    srcs = ["bar.cc"],
+    hdrs = ["inc/bar.h"],
+    visibility = ["//visibility:public"],
+)
+EOF
+  cat > $remote/bar.cc <<EOF
+#include "inc/bar.h"
+int getNum() {
+  return 42;
+}
+EOF
+  cat > $remote/inc/bar.h <<EOF
+int getNum();
+EOF
+
+  cat > WORKSPACE <<EOF
+local_repository(
+    name = "r",
+    path = "$remote",
+)
+EOF
+cat > BUILD <<EOF
+cc_binary(
+    name = "foo",
+    srcs = ["foo.cc"],
+    deps = ["@r//:bar"],
+)
+EOF
+  cat > foo.cc <<EOF
+#include <stdio.h>
+#include "inc/bar.h"
+int main() { printf("%d\n", getNum()); return 0; };
+EOF
+
+  bazel run :foo &> $TEST_log || fail "build failed"
+  expect_log "42"
+}
+
 run_suite "local repository tests"