Add stronger language about pch files and that they shouldn't be used.

--
MOS_MIGRATED_REVID=116017697

1 files changed, 5 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcRuleClasses.java b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcRuleClasses.java
index 1389c5fd78..aa280a2c3d 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcRuleClasses.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcRuleClasses.java
@@ -639,8 +639,11 @@ public class ObjcRuleClasses {
           /* <!-- #BLAZE_RULE($objc_compiling_rule).ATTRIBUTE(pch) -->
            Header file to prepend to every source file being compiled (both arc
            and non-arc).
-           Note that the file will not be precompiled - this is simply a
-           convenience, not a build-speed enhancement.
+           Use of pch files is actively discouraged in BUILD files, and this should be
+           considered deprecated. Since pch files are not actually precompiled this is not
+           a build-speed enhancement, and instead is just a global dependency. From a build
+           efficiency point of view you are actually better including what you need directly
+           in your sources where you need it.
            <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
           .add(attr("pch", LABEL).direct_compile_time_input().allowedFileTypes(FileType.of(".pch")))
           /* <!-- #BLAZE_RULE($objc_compiling_rule).ATTRIBUTE(deps) -->