Make sure a module file with errors produced via '-fallow-pcm-with-compiler-errors' can be loaded when using implicit modules

A module with errors would be marked as out-of-date, then the `compilerModule` action would produce it, but due to the error it would be treated as failure and the resulting PCM would not get used.

rdar://74087062

Differential Revision: https://reviews.llvm.org/D96246

clang/include/clang/Serialization/ASTReader.h

@@ -1543,7 +1543,11 @@ public:
     /// The client can handle an AST file that cannot load because it's
     /// compiled configuration doesn't match that of the context it was
     /// loaded into.
-    ARR_ConfigurationMismatch = 0x8
+    ARR_ConfigurationMismatch = 0x8,
+
+    /// If a module file is marked with errors treat it as out-of-date so the
+    /// caller can rebuild it.
+    ARR_TreatModuleWithErrorsAsOutOfDate = 0x10
   };
 
   /// Load the AST file designated by the given file name.

clang/lib/Frontend/CompilerInstance.cpp

@@ -1144,7 +1144,10 @@ compileModuleImpl(CompilerInstance &ImportingInstance, SourceLocation ImportLoc,
   // module generation thread crashed.
   Instance.clearOutputFiles(/*EraseFiles=*/true);
 
-  return !Instance.getDiagnostics().hasErrorOccurred();
+  // If \p AllowPCMWithCompilerErrors is set return 'success' even if errors
+  // occurred.
+  return !Instance.getDiagnostics().hasErrorOccurred() ||
+         Instance.getFrontendOpts().AllowPCMWithCompilerErrors;
 }
 
 static const FileEntry *getPublicModuleMap(const FileEntry *File,
@@ -1697,7 +1700,8 @@ ModuleLoadResult CompilerInstance::findOrCompileModuleAndReadAST(
   // Try to load the module file. If we are not trying to load from the
   // module cache, we don't know how to rebuild modules.
   unsigned ARRFlags = Source == MS_ModuleCache
-                          ? ASTReader::ARR_OutOfDate | ASTReader::ARR_Missing
+                          ? ASTReader::ARR_OutOfDate | ASTReader::ARR_Missing |
+                                ASTReader::ARR_TreatModuleWithErrorsAsOutOfDate
                           : Source == MS_PrebuiltModulePath
                                 ? 0
                                 : ASTReader::ARR_ConfigurationMismatch;

clang/lib/Serialization/ASTReader.cpp

@@ -2751,8 +2751,9 @@ ASTReader::ReadControlBlock(ModuleFile &F,
 
       bool hasErrors = Record[6];
       if (hasErrors && !DisableValidation) {
-        // Always rebuild modules from the cache on an error
-        if (F.Kind == MK_ImplicitModule)
+        // If requested by the caller, mark modules on error as out-of-date.
+        if (F.Kind == MK_ImplicitModule &&
+            (ClientLoadCapabilities & ARR_TreatModuleWithErrorsAsOutOfDate))
           return OutOfDate;
 
         if (!AllowASTWithCompilerErrors) {

clang/test/Modules/load-module-with-errors.m

@@ -1,3 +1,14 @@
+// Note: the run lines follow their respective tests, since line/column
+// matter in this test.
+
+// pcherror-error@* {{PCH file contains compiler errors}}
+@import error; // notallowerror-error {{could not build module 'error'}}
+// expected-no-diagnostics
+
+void test(Error *x) {
+  [x method];
+}
+
 // RUN: rm -rf %t
 // RUN: mkdir %t
 // RUN: mkdir %t/prebuilt
@@ -48,21 +59,27 @@
 // the verify would fail as it would be the PCH error instead)
 // RUN: %clang_cc1 -fsyntax-only -fmodules \
 // RUN:   -fmodules-cache-path=%t -fimplicit-module-maps -I %S/Inputs/error \
-// RUN:   -x objective-c -verify %s
+// RUN:   -x objective-c -verify=notallowerror %s
 
 // allow-pcm-with-compiler-errors should also allow errors in PCH
 // RUN: %clang_cc1 -fallow-pcm-with-compiler-errors -x objective-c \
 // RUN:   -o %t/check.pch -emit-pch %S/Inputs/error/error.h
 
-// pcherror-error@* {{PCH file contains compiler errors}}
-@import error; // expected-error {{could not build module 'error'}}
-
-void test(Error *x) {
-  [x method];
-}
-
 // CHECK: @interface Error
 // CHECK-NEXT: - (int)method;
 // CHECK-NEXT: - (id)method2;
 // CHECK-NEXT: @end
 // CHECK: void test(Error *x)
+
+// RUN: c-index-test -code-completion-at=%s:9:6 %s -fmodules -fmodules-cache-path=%t \
+// RUN:   -Xclang -fallow-pcm-with-compiler-errors -I %S/Inputs/error | FileCheck -check-prefix=COMPLETE %s
+// COMPLETE: ObjCInstanceMethodDecl:{ResultType int}{TypedText method}
+// COMPLETE: ObjCInstanceMethodDecl:{ResultType id}{TypedText method2}
+
+// RUN: c-index-test -test-load-source local %s -fmodules -fmodules-cache-path=%t \
+// RUN:   -Xclang -fallow-pcm-with-compiler-errors -I %S/Inputs/error | FileCheck -check-prefix=SOURCE %s
+// SOURCE: load-module-with-errors.m:8:6: FunctionDecl=test:8:6 (Definition) Extent=[8:1 - 10:2]
+// SOURCE: load-module-with-errors.m:8:18: ParmDecl=x:8:18 (Definition) Extent=[8:11 - 8:19]
+// SOURCE: load-module-with-errors.m:8:11: ObjCClassRef=Error:3:12 Extent=[8:11 - 8:16]
+// SOURCE: load-module-with-errors.m:8:21: CompoundStmt= Extent=[8:21 - 10:2]
+// SOURCE: load-module-with-errors.m:9:3: ObjCMessageExpr=method:4:8 Extent=[9:3 - 9:13]