Makes the error message for invalid or duplicate crosstool toolchains more legible by putting each flag combination on its own line.

E.g. from this:

ERROR: No toolchain found for --cpu='foo' --compiler='bar' --glibc='baz'. Valid toolchains are: [ --cpu='armeabi-v7a' --compiler='compiler' --glibc='armeabi-v7a', --cpu='armeabi-v7a' --compiler='compiler' --glibc='armeabi-v7a', --cpu='local' --compiler='compiler' --glibc='local', --cpu='darwin' --compiler='compiler' --glibc='macosx', --cpu='freebsd' --compiler='compiler' --glibc='local', --cpu='k8' --compiler='windows_mingw' --glibc='local', --cpu='k8' --compiler='windows_msys64_mingw64' --glibc='local', --cpu='k8' --compiler='windows_clang' --glibc='local',].

to this:

ERROR: No toolchain found for --cpu='foo' --compiler='bar' --glibc='baz'. Valid toolchains are: [
  --cpu='armeabi-v7a' --compiler='compiler' --glibc='armeabi-v7a',
  --cpu='armeabi-v7a' --compiler='compiler' --glibc='armeabi-v7a',
  --cpu='local' --compiler='compiler' --glibc='local',
  --cpu='darwin' --compiler='compiler' --glibc='macosx',
  --cpu='freebsd' --compiler='compiler' --glibc='local',
  --cpu='k8' --compiler='windows_mingw' --glibc='local',
  --cpu='k8' --compiler='windows_msys64_mingw64' --glibc='local',
  --cpu='k8' --compiler='windows_clang' --glibc='local',
].

(notice there is a duplicate toolchain)

--
MOS_MIGRATED_REVID=105313547

1 files changed, 5 insertions, 7 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CrosstoolConfigurationLoader.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CrosstoolConfigurationLoader.java
index febbdacc77..6a42fce772 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CrosstoolConfigurationLoader.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CrosstoolConfigurationLoader.java
@@ -347,20 +347,18 @@ public class CrosstoolConfigurationLoader {
         + "corresponding to '" + selectedIdentifier + "' found for cpu '" + config.getCpu() + "'");
   }
 
-  private static String describeToolchainFlags(CrosstoolConfig.CToolchain toolchain) {
-    return CrosstoolConfigurationIdentifier.fromToolchain(toolchain).describeFlags();
-  }
-
   /**
    * Appends a series of toolchain descriptions (as the blaze command line flags
    * that would specify that toolchain) to 'message'.
    */
   private static void describeToolchainList(StringBuilder message,
       Collection<CrosstoolConfig.CToolchain> toolchains) {
-    message.append("[");
+    message.append("[\n");
     for (CrosstoolConfig.CToolchain toolchain : toolchains) {
-      message.append(describeToolchainFlags(toolchain));
-      message.append(",");
+      message.append("  ");
+      message.append(
+          CrosstoolConfigurationIdentifier.fromToolchain(toolchain).describeFlags().trim());
+      message.append(",\n");
     }
     message.append("]");
   }