From a413c8236f6c7add235e9555966c537a72a79f2d Mon Sep 17 00:00:00 2001
From: Googler <gregce@google.com>
Date: Thu, 6 Jul 2023 10:20:32 -0700
Subject: [PATCH] Adjust --top_level_targets_for_symlinks.

Old semantics:

New semantics:

Fixes https://github.com/bazelbuild/bazel/issues/17081.

PiperOrigin-RevId: 546025529
Change-Id: I095564bb9233eba4b008df7f9e6aedae3e973b23
---
 .../build/lib/buildtool/ExecutionTool.java    | 41 ++++++++++++++-----
 .../buildtool/OutputDirectoryLinksUtils.java  |  4 +-
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java b/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java
index 3a871c2901af85..1e565e44633a53 100644
--- a/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java
+++ b/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java
@@ -766,16 +766,35 @@ private ImmutableList<ConvenienceSymlink> createConvenienceSymlinks(
     Reporter reporter = env.getReporter();
 
     // Gather configurations to consider.
-    Set<BuildConfigurationValue> targetConfigurations =
-        buildRequestOptions.useTopLevelTargetsForSymlinks() && !targetsToBuild.isEmpty()
-            ? targetsToBuild.stream()
-                .map(ConfiguredTarget::getActual)
-                .map(ConfiguredTarget::getConfigurationKey)
-                .filter(Objects::nonNull)
-                .distinct()
-                .map((key) -> executor.getConfiguration(reporter, key))
-                .collect(toImmutableSet())
-            : ImmutableSet.of(configuration);
+    ImmutableSet<BuildConfigurationValue> targetConfigs;
+    if (buildRequestOptions.useTopLevelTargetsForSymlinks() && !targetsToBuild.isEmpty()) {
+      // Collect the configuration of each top-level requested target. These may be different than
+      // the build's top-level configuration because of self-transitions.
+      ImmutableSet<BuildConfigurationValue> requestedTargetConfigs =
+          targetsToBuild.stream()
+              .map(ConfiguredTarget::getActual)
+              .map(ConfiguredTarget::getConfigurationKey)
+              .filter(Objects::nonNull)
+              .distinct()
+              .map((key) -> executor.getConfiguration(reporter, key))
+              .collect(toImmutableSet());
+      if (requestedTargetConfigs.size() == 1) {
+        // All top-level targets have the same configuration, so use that one.
+        targetConfigs = requestedTargetConfigs;
+      } else if (requestedTargetConfigs.contains(configuration)) {
+        // Mixed configs but at least one of them includes the top-level config. Set symlinks to the
+        // top-level config so at least non-transitioned targets resolve. See
+        // https://github.com/bazelbuild/bazel/issues/17081.
+        targetConfigs = ImmutableSet.of(configuration);
+      } else {
+        // Mixed configs, none of which include the top-level config. Delete the symlinks because
+        // they won't contain any relevant data. This is handled in the
+        // createOutputDirectorySymlinks call below.
+        targetConfigs = requestedTargetConfigs;
+      }
+    } else {
+      targetConfigs = ImmutableSet.of(configuration);
+    }
 
     String productName = runtime.getProductName();
     try (SilentCloseable c =
@@ -787,7 +806,7 @@ private ImmutableList<ConvenienceSymlink> createConvenienceSymlinks(
           env.getWorkspace(),
           env.getDirectories(),
           getReporter(),
-          targetConfigurations,
+          targetConfigs,
           options -> getConfiguration(executor, reporter, options),
           productName);
     }
diff --git a/src/main/java/com/google/devtools/build/lib/buildtool/OutputDirectoryLinksUtils.java b/src/main/java/com/google/devtools/build/lib/buildtool/OutputDirectoryLinksUtils.java
index 47ba5a408ff0f3..23cf130bd66a75 100644
--- a/src/main/java/com/google/devtools/build/lib/buildtool/OutputDirectoryLinksUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/buildtool/OutputDirectoryLinksUtils.java
@@ -169,7 +169,9 @@ static ImmutableList<ConvenienceSymlink> createOutputDirectoryLinks(
       eventHandler.handle(
           Event.warn(
               String.format(
-                  "cleared convenience symlink(s) %s because their destinations would be ambiguous",
+                  "cleared convenience symlink(s) %s because they wouldn't contain 0 "
+                      + "requested targets' outputs. Those targets self-transition to multiple "
+                      + "distinct configurations",
                   Joiner.on(", ").join(ambiguousLinks))));
     }
     return convenienceSymlinksBuilder.build();