Resolve repository-relative labels within the current repository

Using $(location //foo) from an external repository was resolving to @//foo, not
@repo//foo, which generally wouldn't be in the main repository. This may also
fix other cases where getRelative was resolving incorrectly.

Fixes #819.

--
MOS_MIGRATED_REVID=113256854

3 files changed, 15 insertions, 16 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/Label.java b/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
index 7e1046f8a1..b1bcffa482 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/Label.java
@@ -49,6 +49,8 @@ public final class Label implements Comparable<Label>, Serializable, SkylarkPrin
    * things to Bazel.
    */
   private static final ImmutableSet<PathFragment> ABSOLUTE_PACKAGE_NAMES = ImmutableSet.of(
+      // Used for select
+      new PathFragment("conditions"),
       // dependencies that are a function of the configuration
       new PathFragment("tools/defaults"),
       // Visibility is labels aren't actually targets
@@ -370,18 +372,26 @@ public final class Label implements Comparable<Label>, Serializable, SkylarkPrin
    */
   @SkylarkCallable(name = "relative", doc =
         "Resolves a label that is either absolute (starts with <code>//</code>) or relative to the"
-      + " current package.<br>"
+      + " current package. If this label is in a remote repository, the argument will be resolved "
+      + "relative to that repository. If the argument contains a repository, it will be returned "
+      + "as-is. Reserved labels will also be returned as-is.<br>"
       + "For example:<br>"
       + "<pre class=language-python>\n"
       + "Label(\"//foo/bar:baz\").relative(\":quux\") == Label(\"//foo/bar:quux\")\n"
       + "Label(\"//foo/bar:baz\").relative(\"//wiz:quux\") == Label(\"//wiz:quux\")\n"
+      + "Label(\"@repo//foo/bar:baz\").relative(\"//wiz:quux\") == Label(\"@repo//wiz:quux\")\n"
+      + "Label(\"@repo//foo/bar:baz\").relative(\"//visibility:public\") == "
+      + "Label(\"//visibility:public\")\n"
+      + "Label(\"@repo//foo/bar:baz\").relative(\"@other//wiz:quux\") == "
+      + "Label(\"@other//wiz:quux\")\n"
       + "</pre>")
   public Label getRelative(String relName) throws LabelSyntaxException {
     if (relName.length() == 0) {
       throw new LabelSyntaxException("empty package-relative label");
     }
+
     if (LabelValidator.isAbsolute(relName)) {
-      return parseAbsolute(relName);
+      return resolveRepositoryRelative(parseAbsolute(relName));
     } else if (relName.equals(":")) {
       throw new LabelSyntaxException("':' is not a valid package-relative label");
     } else if (relName.charAt(0) == ':') {
@@ -399,18 +409,6 @@ public final class Label implements Comparable<Label>, Serializable, SkylarkPrin
    * repository would point back to the main repository, which is usually not what is intended.
    */
   public Label resolveRepositoryRelative(Label relative) {
-    if (relative.packageIdentifier.getRepository().getName().equals("@")) {
-      try {
-        return new Label(
-            PackageIdentifier.create(
-                PackageIdentifier.DEFAULT_REPOSITORY_NAME,
-                relative.packageIdentifier.getPackageFragment()),
-            relative.getName());
-      } catch (LabelSyntaxException e) {
-        throw new IllegalStateException(e);
-      }
-    }
-
     if (packageIdentifier.getRepository().isDefault()
         || !relative.packageIdentifier.getRepository().isDefault()
         || ABSOLUTE_PACKAGE_NAMES.contains(relative.getPackageIdentifier().getPackageFragment())) {
diff --git a/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java b/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
index 2aa253dcb1..6f5811d58a 100644
--- a/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
+++ b/src/main/java/com/google/devtools/build/lib/cmdline/RepositoryName.java
@@ -189,7 +189,7 @@ public final class RepositoryName implements Serializable {
    * Returns the path at which this repository is mapped within the exec root.
    */
   public PathFragment getPathFragment() {
-    return isDefault()
+    return isDefault() || this.equals(PackageIdentifier.MAIN_REPOSITORY_NAME)
         ? PathFragment.EMPTY_FRAGMENT
         : new PathFragment(Label.EXTERNAL_PATH_PREFIX).getRelative(strippedName());
   }
diff --git a/src/main/java/com/google/devtools/build/lib/packages/Package.java b/src/main/java/com/google/devtools/build/lib/packages/Package.java
index 51a496dc7a..1cfb443936 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/Package.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/Package.java
@@ -267,7 +267,8 @@ public class Package {
 
   private static Path getSourceRoot(Path buildFile, PathFragment packageFragment) {
     Path current = buildFile.getParentDirectory();
-    for (int i = 0, len = packageFragment.segmentCount(); i < len && current != null; i++) {
+    for (int i = 0, len = packageFragment.segmentCount();
+         i < len && !packageFragment.equals(PathFragment.EMPTY_FRAGMENT); i++) {
       current = current.getParentDirectory();
     }
     return current;