doc-serialization: diagnose missing group-info file or corrupted one.

include/swift/AST/DiagnosticsCommon.def

@@ -50,6 +50,12 @@ ERROR(not_implemented,none,
 ERROR(error_opening_output,none,
       "error opening '%0' for output: %1", (StringRef, StringRef))
 
+ERROR(cannot_find_group_info_file,none,
+      "cannot find group info file at path: '%0'", (StringRef))
+
+ERROR(cannot_parse_group_info_file,none,
+      "cannot parse group info file at path: '%0'", (StringRef))
+
 ERROR(error_no_group_info,none,
       "no group info found for file: '%0'", (StringRef))
 

lib/Serialization/SerializeDoc.cpp

@@ -38,6 +38,7 @@ using pFileNameToGroupNameMap = std::unique_ptr<FileNameToGroupNameMap>;
 
 namespace {
 class YamlGroupInputParser {
+  ASTContext &Ctx;
   StringRef RecordPath;
   static constexpr const char * const Separator = "/";
 
@@ -86,12 +87,20 @@ class YamlGroupInputParser {
   }
 
 public:
-  YamlGroupInputParser(StringRef RecordPath): RecordPath(RecordPath) {}
+  YamlGroupInputParser(ASTContext &Ctx, StringRef RecordPath):
+    Ctx(Ctx), RecordPath(RecordPath) {}
 
   FileNameToGroupNameMap* getParsedMap() {
     return AllMaps[RecordPath].get();
   }
 
+  bool diagnoseGroupInfoFile(bool FileMissing = false) {
+    Ctx.Diags.diagnose(SourceLoc(),
+      FileMissing ? diag::cannot_find_group_info_file:
+      diag::cannot_parse_group_info_file, RecordPath);
+    return true;
+  }
+
   // Parse the Yaml file that contains the group information.
   // True on failure; false on success.
   bool parse() {
@@ -102,32 +111,31 @@ class YamlGroupInputParser {
 
     auto Buffer = llvm::MemoryBuffer::getFile(RecordPath);
     if (!Buffer) {
-      // The group info file does not exist.
-      return true;
+      return diagnoseGroupInfoFile(/*Missing File*/true);
     }
     llvm::SourceMgr SM;
     llvm::yaml::Stream YAMLStream(Buffer.get()->getMemBufferRef(), SM);
     llvm::yaml::document_iterator I = YAMLStream.begin();
     if (I == YAMLStream.end()) {
       // Cannot parse correctly.
-      return true;
+      return diagnoseGroupInfoFile();
     }
     llvm::yaml::Node *Root = I->getRoot();
     if (!Root) {
       // Cannot parse correctly.
-      return true;
+      return diagnoseGroupInfoFile();
     }
 
     // The format is a map of ("group0" : ["file1", "file2"]), meaning all
     // symbols from file1 and file2 belong to "group0".
     auto *Map = dyn_cast<llvm::yaml::MappingNode>(Root);
     if (!Map) {
-      return true;
+      return diagnoseGroupInfoFile();
     }
     pFileNameToGroupNameMap pMap(new FileNameToGroupNameMap());
     std::string Empty;
     if (parseRoot(*pMap, Root, Empty))
-      return true;
+      return diagnoseGroupInfoFile();
 
     // Save the parsed map to the owner.
     AllMaps[RecordPath] = std::move(pMap);
@@ -168,7 +176,7 @@ class DeclGroupNameContext {
       StringRef FullPath =
           Ctx.SourceMgr.getIdentifierForBuffer(PathOp.getValue());
       if (!pMap) {
-        YamlGroupInputParser Parser(RecordPath);
+        YamlGroupInputParser Parser(Ctx, RecordPath);
         if (!Parser.parse()) {
 
           // Get the file-name to group map if parsing correctly.

test/Serialization/Inputs/corrupted_group_info.json

@@ -0,0 +1,3 @@
+{
+	corrupteddata
+}

test/Serialization/group_info_diags.swift

@@ -0,0 +1,10 @@
+// RUN: %empty-directory(%t)
+// RUN: not %target-swift-frontend -emit-module %s -module-name HasArray -o %t -module-cache-path %t/mcp -group-info-path %t/nonexist.json -emit-module-doc &> %t/result.txt
+// RUN: %FileCheck %s -check-prefix=MISSING < %t/result.txt
+// RUN: not %target-swift-frontend -emit-module %s -module-name HasArray -o %t -module-cache-path %t/mcp -group-info-path %S/Inputs/corrupted_group_info.json -emit-module-doc &> %t/result.txt
+// RUN: %FileCheck %s -check-prefix=CORRUPTED < %t/result.txt
+
+public protocol P {}
+
+// MISSING: error: cannot find group info file at path
+// CORRUPTED: error: cannot parse group info file at path