[Serialization] Ignore filesystem errors when loading modules. (#4547)

Instead, just go on to the next search path. This prevents a
present-but-unreadable directory from leading to a module load
failure, which happens when one user builds a module and another user
loads it (even if those search paths aren't even being used).

There might still be some other errors that would be useful to treat
as "module found but invalid" rather than "module not found", but
experience has shown that it's the wrong default.

There is a Radar for this but I can't find it.

Author: jrose-apple

lib/Serialization/SerializedModuleLoader.cpp

@@ -67,7 +67,7 @@ openModuleFiles(StringRef DirName, StringRef ModuleFilename,
   return std::error_code();
 }
 
-static std::error_code
+static bool
 findModule(ASTContext &ctx, AccessPathElem moduleID,
            std::unique_ptr<llvm::MemoryBuffer> &moduleBuffer,
            std::unique_ptr<llvm::MemoryBuffer> &moduleDocBuffer,
@@ -110,8 +110,8 @@ findModule(ASTContext &ctx, AccessPathElem moduleID,
                             moduleBuffer, moduleDocBuffer,
                             scratch);
     }
-    if (!err || err != std::errc::no_such_file_or_directory)
-      return err;
+    if (!err)
+      return true;
   }
 
   {
@@ -127,20 +127,20 @@ findModule(ASTContext &ctx, AccessPathElem moduleID,
                                  archFile.str(), archDocFile.str(),
                                  moduleBuffer, moduleDocBuffer,
                                  scratch);
-      if (!err || err != std::errc::no_such_file_or_directory)
-        return err;
+      if (!err)
+        return true;
     }
   }
 
   // If we're not allowed to look in the runtime library import path, stop.
   if (ctx.SearchPathOpts.SkipRuntimeLibraryImportPath)
-    return std::make_error_code(std::errc::no_such_file_or_directory);
+    return false;
 
   // Search the runtime import path.
   isFramework = false;
-  return openModuleFiles(ctx.SearchPathOpts.RuntimeLibraryImportPath,
-                         moduleFilename.str(), moduleDocFilename.str(),
-                         moduleBuffer, moduleDocBuffer, scratch);
+  return !openModuleFiles(ctx.SearchPathOpts.RuntimeLibraryImportPath,
+                          moduleFilename.str(), moduleDocFilename.str(),
+                          moduleBuffer, moduleDocBuffer, scratch);
 }
 
 FileUnit *SerializedModuleLoader::loadAST(
@@ -378,14 +378,8 @@ Module *SerializedModuleLoader::loadModule(SourceLoc importLoc,
 
   // Otherwise look on disk.
   if (!moduleInputBuffer) {
-    if (std::error_code err = findModule(Ctx, moduleID, moduleInputBuffer,
-                                         moduleDocInputBuffer,
-                                         isFramework)) {
-      if (err != std::errc::no_such_file_or_directory) {
-        Ctx.Diags.diagnose(moduleID.second, diag::sema_opening_import,
-                           moduleID.first, err.message());
-      }
-
+    if (!findModule(Ctx, moduleID, moduleInputBuffer, moduleDocInputBuffer,
+                    isFramework)) {
       return nullptr;
     }
 

test/Serialization/load-file-permissions.swift

@@ -0,0 +1,10 @@
+// RUN: if [[ -d %t ]]; then chmod -R u+rwx %t && rm -rf %t; fi
+// RUN: mkdir -p %t/good
+// RUN: mkdir %t/bad
+// RUN: chmod a-rx %t/bad
+// RUN: %target-swift-frontend -emit-module -o %t/good %S/../Inputs/empty.swift
+// RUN: not %target-swift-frontend %s -parse -I %t/bad -I %t/good -show-diagnostics-after-fatal 2>&1 | %FileCheck %s
+// RUN: not %target-swift-frontend %s -parse -I %t/good -I %t/bad -show-diagnostics-after-fatal 2>&1 | %FileCheck %s
+
+import empty // CHECK-NOT: empty
+import ThisOneReallyDoesNotExist // CHECK: [[@LINE]]:{{[0-9]+}}: error: no such module 'ThisOneReallyDoesNotExist'