[driver] Additional ignoring of module-map related flags, if modules are disabled

[MaskRay]

I sometimes need to debug builds by disabling modules. This behavior will make debugging easier.

clang/test/Driver/modules.m

77–78

You may combine -fmodule-map-file=module.modulemap with this RUN line to avoid introducing a new RUN line (every run makes testsuite slightly slower).

[akyrtzi]

Merge the new RUN line together with the prior 2.

[akyrtzi]

clang/test/Driver/modules.m

77–78

Good suggestion, I merged the last existing 2 RUN lines along with the new one.

[rsmith]

This doesn't look right to me -- we still use module maps when modules are disabled to enforce layering checking, and when -fmodules-local-submodule-visibility is enabled but -fmodules is disabled we'll use them to provide modular semantics without pre-building modules. I'm going to revert.

[akyrtzi]

In D132801#3760014, @rsmith wrote:

This doesn't look right to me -- we still use module maps when modules are disabled to enforce layering checking, and when -fmodules-local-submodule-visibility is enabled but -fmodules is disabled we'll use them to provide modular semantics without pre-building modules. I'm going to revert.

Sorry, I wasn't aware of that. Could -fmodule-map-file= be pruned out when -fmodules-local-submodule-visibility or -fmodules-decluse are not enabled?

[akyrtzi]

In D132801#3761253, @akyrtzi wrote:

In D132801#3760014, @rsmith wrote:

This doesn't look right to me -- we still use module maps when modules are disabled to enforce layering checking, and when -fmodules-local-submodule-visibility is enabled but -fmodules is disabled we'll use them to provide modular semantics without pre-building modules. I'm going to revert.

Sorry, I wasn't aware of that. Could -fmodule-map-file= be pruned out when -fmodules-local-submodule-visibility or -fmodules-decluse are not enabled?

I've opened https://reviews.llvm.org/D133229 for your consideration, let me know whether this addresses your concerns 🙏

clang/lib/Driver/ToolChains/Clang.cpp

if (HaveModules) {
     }
     if (Args.hasFlag(options::OPT_fprebuilt_implicit_modules,
                      options::OPT_fno_prebuilt_implicit_modules, false))
       CmdArgs.push_back("-fprebuilt-implicit-modules");
     if (Args.hasFlag(options::OPT_fmodules_validate_input_files_content,
                      options::OPT_fno_modules_validate_input_files_content,
                      false))
       CmdArgs.push_back("-fvalidate-ast-input-files-content");
-  }
 
     // -fmodule-name specifies the module that is currently being built (or
     // used for header checking by -fmodule-maps).
     Args.AddLastArg(CmdArgs, options::OPT_fmodule_name_EQ);
 
     // -fmodule-map-file can be used to specify files containing module
     // definitions.
     Args.AddAllArgs(CmdArgs, options::OPT_fmodule_map_file);
 
     // -fbuiltin-module-map can be used to load the clang
     // builtin headers modulemap file.
     if (Args.hasArg(options::OPT_fbuiltin_module_map)) {
       SmallString<128> BuiltinModuleMap(D.ResourceDir);
       llvm::sys::path::append(BuiltinModuleMap, "include");
       llvm::sys::path::append(BuiltinModuleMap, "module.modulemap");
       if (llvm::sys::fs::exists(BuiltinModuleMap))
         CmdArgs.push_back(
             Args.MakeArgString("-fmodule-map-file=" + BuiltinModuleMap));
     }
+  } else {
+    Args.ClaimAllArgs(options::OPT_fmodule_name_EQ);
+    Args.ClaimAllArgs(options::OPT_fmodule_map_file);
+    Args.ClaimAllArgs(options::OPT_fbuiltin_module_map);
+  }
 
   // The -fmodule-file=<name>=<file> form specifies the mapping of module
   // names to precompiled module files (the module is loaded only if used).
   // The -fmodule-file=<file> form can be used to unconditionally load
   // precompiled module files (whether used or not).
   if (HaveModules)
     Args.AddAllArgs(CmdArgs, options::OPT_fmodule_file);
   else

clang/test/Driver/modules.m

 // RUN: %clang -fno-modules -fmodule-file=foo.pcm -fmodule-file=bar.pcm -### %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MODULE-FILES %s
 // CHECK-NO-MODULE-FILES-NOT: "-fmodules"
 // CHECK-NO-MODULE-FILES-NOT: "-fmodule-file=foo.pcm"
 // CHECK-NO-MODULE-FILES-NOT: "-fmodule-file=bar.pcm"
 
 // RUN: %clang -fno-modules -fbuild-session-file=%t.build-session-file -### %s 2>&1 | FileCheck -check-prefix=SESSION_FLAG %s
 // RUN: %clang -fno-modules -fbuild-session-timestamp=123 -### %s 2>&1 | FileCheck -check-prefix=SESSION_FLAG %s
 // SESSION_FLAG-NOT: -fbuild-session-timestamp
 
-// RUN: %clang -fno-modules -fmodules-validate-once-per-build-session -### %s 2>&1 | FileCheck -check-prefix=VALIDATE_ONCE_FLAG %s
-// VALIDATE_ONCE_FLAG-NOT: -fmodules-validate-once-per-build-session
-
-// RUN: %clang -fno-modules -fmodules-validate-system-headers -### %s 2>&1 | FileCheck -check-prefix=VALIDATE_SYSTEM_FLAG %s
-// VALIDATE_SYSTEM_FLAG-NOT: -fmodules-validate-system-headers
+// RUN: %clang -fno-modules -fmodules-validate-once-per-build-session -fmodules-validate-system-headers -fmodule-map-file=module.modulemap \
+// RUN:   -### %s 2>&1 | FileCheck -check-prefix=IGNORED_FLAGS %s
+// IGNORED_FLAGS-NOT: -fmodules-validate-once-per-build-session
+// IGNORED_FLAGS-NOT: -fmodules-validate-system-headers
+// IGNORED_FLAGS-NOT: -fmodule-map-file