Properly account for symlinks and root symlinks in repo mapping manifest
A runfiles symlink entry `path/to/pkg/file -> path/to/artifact` is implicitly prefixed with the workspace name and should thus result in repo mappings to the main repository being added to the repo mapping manifest, not mappings for the owner of the artifact.
A runfiles root symlink entry `first_segment/path/to/pkg/file -> path/to/artifact` should result result in repo mappings to the repository with canonical name equal to the first segment being added to the repo mapping manifest, if such a repository exists.
Along the way clarifies in the documentation of `ctx.runfiles(symlinks = ...)` that the workspace name will be prefixed implicitly.
Closes #18381.
PiperOrigin-RevId: 541934743
Change-Id: I2931772c3b337d76e65fd81e4a6b783ed80ac05b
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/SymlinkEntry.java b/src/main/java/com/google/devtools/build/lib/analysis/SymlinkEntry.java
new file mode 100644
index 0000000..619309f
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/analysis/SymlinkEntry.java
@@ -0,0 +1,88 @@
+// Copyright 2014 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.devtools.build.lib.analysis;
+
+import com.google.common.base.Preconditions;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.starlarkbuildapi.SymlinkEntryApi;
+import com.google.devtools.build.lib.vfs.PathFragment;
+import net.starlark.java.eval.Printer;
+
+/**
+ * An entry in the runfiles map.
+ *
+ * <p>build-runfiles.cc enforces the following constraints: The PathFragment must not be an absolute
+ * path, nor contain "..". Overlapping runfiles links are also refused. This is the case where you
+ * ask to create a link to "foo" and also "foo/bar.txt". I.e. you're asking it to make "foo" both a
+ * file (symlink) and a directory.
+ *
+ * <p>Links to directories are heavily discouraged.
+ */
+//
+// O intrepid fixer or bugs and implementor of features, dare not to add a .equals() method
+// to this class, lest you condemn yourself, or a fellow other developer to spending two
+// delightful hours in a fancy hotel on a Chromebook that is utterly unsuitable for Java
+// development to figure out what went wrong, just like I just did.
+//
+// The semantics of the symlinks nested set dictates that later entries overwrite earlier
+// ones. However, the semantics of nested sets dictate that if there are duplicate entries, they
+// are only returned once in the iterator.
+//
+// These two things, innocent when taken alone, result in the effect that when there are three
+// entries for the same path, the first one and the last one the same, and the middle one
+// different, the *middle* one will take effect: the middle one overrides the first one, and the
+// first one prevents the last one from appearing on the iterator.
+//
+// The lack of a .equals() method prevents this by making the first entry in the above case not
+// equal to the third one if they are not the same instance (which they almost never are).
+//
+// Goodnight, prince(ss)?, and sweet dreams.
+public final class SymlinkEntry implements SymlinkEntryApi {
+ private final PathFragment path;
+ private final Artifact artifact;
+
+ SymlinkEntry(PathFragment path, Artifact artifact) {
+ this.path = Preconditions.checkNotNull(path);
+ this.artifact = Preconditions.checkNotNull(artifact);
+ }
+
+ @Override
+ public String getPathString() {
+ return path.getPathString();
+ }
+
+ public PathFragment getPath() {
+ return path;
+ }
+
+ @Override
+ public Artifact getArtifact() {
+ return artifact;
+ }
+
+ @Override
+ public boolean isImmutable() {
+ return true;
+ }
+
+ @Override
+ public void repr(Printer printer) {
+ printer.append("SymlinkEntry(path = ");
+ printer.repr(getPathString());
+ printer.append(", target_file = ");
+ artifact.repr(printer);
+ printer.append(")");
+ }
+}
