[Clang] Allow explicitly building an inferred module.

Building the actual module still fails, but make sure it fails for the
right reason.

Author: Bigcheese

clang/lib/Frontend/FrontendAction.cpp

@@ -461,7 +461,7 @@ static Module *prepareToBuildModule(CompilerInstance &CI,
   // Dig out the module definition.
   HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();
   Module *M = HS.lookupModule(CI.getLangOpts().CurrentModule,
-                              /*AllowSearch=*/false);
+                              /*AllowSearch=*/true);
   if (!M) {
     CI.getDiagnostics().Report(diag::err_missing_module)
       << CI.getLangOpts().CurrentModule << ModuleMapFilename;

clang/test/ClangScanDeps/module-deps-to-rsp.py

@@ -0,0 +1,76 @@
+#!/usr/bin/env python
+
+import argparse
+import json
+import sys
+
+class ModuleNotFoundError(Exception):
+  def __init__(self, module_name):
+    self.module_name = module_name
+
+class FullDeps:
+  def __init__(self):
+    self.modules = dict()
+    self.translation_units = str()
+    
+def getModulePathArgs(modules, full_deps):
+  cmd = []
+  for md in modules:
+    m = full_deps.modules[md['module-name'] + '-' + md['context-hash']]
+    cmd += [u'-fmodule-map-file=' + m['clang-modulemap-file']]
+    cmd += [u'-fmodule-file=' + md['module-name'] + '-' + md['context-hash'] + '.pcm']
+  return cmd
+
+def getCommandLineForModule(module_name, full_deps):
+  for m in full_deps.modules.values():
+    if m['name'] == module_name:
+      module = m
+      break
+  else:
+    raise ModuleNotFoundError(module_name)
+
+  cmd = m['command-line']
+  cmd += getModulePathArgs(m['clang-module-deps'], full_deps)
+  cmd += [u'-o', m['name'] + '-' + m['context-hash'] + '.pcm']
+  cmd += [m['clang-modulemap-file']]
+  
+  return cmd
+  
+def getCommandLineForTU(tu, full_deps):
+  cmd = tu['command-line']
+  cmd = [a for a in cmd if not (a.startswith('-fmodule-map-file=') or a.startswith('-fmodule-file='))]
+  cmd += getModulePathArgs(tu['clang-module-deps'], full_deps)
+  return cmd
+
+def parseFullDeps(json):
+  ret = FullDeps()
+  for m in json['modules']:
+    ret.modules[m['name'] + '-' + m['context-hash']] = m
+  ret.translation_units = json['translation-units']
+  return ret
+
+def main():
+  parser = argparse.ArgumentParser()
+  parser.add_argument("full_deps_file", help="Path to the full dependencies json file",
+                      type=str)
+  action = parser.add_mutually_exclusive_group(required=True)
+  action.add_argument("--module-name", help="The name of the module to get arguments for",
+                      type=str)
+  action.add_argument("--tu-index", help="The index of the translation unit to get arguments for",
+                      type=int)
+  args = parser.parse_args()
+  
+  full_deps = parseFullDeps(json.load(open(args.full_deps_file, 'r')))
+  
+  try:
+    if args.module_name:
+      print(" ".join(getCommandLineForModule(args.module_name, full_deps)))
+    
+    elif args.tu_index != None:
+      print(" ".join(getCommandLineForTU(full_deps.translation_units[args.tu_index], full_deps)))
+  except:
+    print("Unexpected error:", sys.exc_info()[0])
+    raise
+
+if __name__ == '__main__':
+  main()

clang/test/ClangScanDeps/modules-inferred-explicit-build.m

@@ -0,0 +1,17 @@
+// RUN: rm -rf %t.dir
+// RUN: rm -rf %t.cdb
+// RUN: mkdir -p %t.dir
+// RUN: cp %s %t.dir/modules_cdb_input.cpp
+// RUN: sed -e "s|DIR|%/t.dir|g" -e "s|FRAMEWORKS|%/S/Inputs/frameworks|g" \
+// RUN:   %S/Inputs/modules_inferred_cdb.json > %t.cdb
+//
+// RUN: clang-scan-deps -compilation-database %t.cdb -j 1 -full-command-line \
+// RUN:   -mode preprocess-minimized-sources -format experimental-full > %t.db
+// RUN: %S/module-deps-to-rsp.py %t.db --module-name=Inferred > %t.inferred.rsp
+// RUN: %S/module-deps-to-rsp.py %t.db --tu-index=0 > %t.tu.rsp
+// RUN: not %clang_cc1 -E %t.dir/modules_cdb_input.cpp -F%S/Inputs/frameworks -fmodules -fimplicit-module-maps @%t.inferred.rsp 2>&1 | grep "'Inferred.h' file not found"
+// RUN: not %clang_cc1 -E %t.dir/modules_cdb_input.cpp -F%S/Inputs/frameworks -fmodules -fimplicit-module-maps @%t.tu.rsp
+
+#include <Inferred/Inferred.h>
+
+inferred a = 0;