[autocompletion] Handle the space before pressing tab

[yamaguchi]

Summary

Distinguish "--autocomplete=-someflag" and "--autocomplete=-someflag,"
because the latter indicates that the user put space before pushing tab
which should end up in a file completion.

[teemperor]

clang/lib/Driver/Driver.cpp

1514

Why not const bool HasSpace = PassedFlags.endswith(",")?

1537

Can you describe in the comment why printing a newline and returning here is the correct behavior? It's not obvious to the reader (including me).

[yamaguchi]

Updated HasSpace, added comments, fixed typo in the commit message

[teemperor]

LGTM!

clang/lib/Driver/Driver.cpp

void Driver::HandleAutocompletions(StringRef PassedFlags) const {
   // Print out all options that start with a given argument. This is used for
   // shell autocompletion.
   std::vector<std::string> SuggestedCompletions;
   std::vector<std::string> Flags;
 
   unsigned short DisableFlags =
       options::NoDriverOption | options::Unsupported | options::Ignored;
 
+  // Distinguish "--autocomplete=-someflag" and "--autocomplete=-someflag,"
+  // because the latter indicates that the user put space before pushing tab
+  // which should end up in a file completion.
+  const bool HasSpace = PassedFlags.endswith(",");
+
   // Parse PassedFlags by "," as all the command-line flags are passed to this
   // function separated by ","
   StringRef TargetFlags = PassedFlags;
   while (TargetFlags != "") {
     StringRef CurFlag;
     std::tie(CurFlag, TargetFlags) = TargetFlags.split(",");
     Flags.push_back(std::string(CurFlag));
   }
 
   // We want to show cc1-only options only when clang is invoked with -cc1 or
   // -Xclang.
   if (std::find(Flags.begin(), Flags.end(), "-Xclang") != Flags.end() ||
       std::find(Flags.begin(), Flags.end(), "-cc1") != Flags.end())
     DisableFlags &= ~options::NoDriverOption;
 
   StringRef Cur;
   Cur = Flags.at(Flags.size() - 1);
   StringRef Prev;
   if (Flags.size() >= 2) {
     Prev = Flags.at(Flags.size() - 2);
     SuggestedCompletions = Opts->suggestValueCompletions(Prev, Cur);
   }
 
   if (SuggestedCompletions.empty())
     SuggestedCompletions = Opts->suggestValueCompletions(Cur, "");
 
+  // If Flags were empty, it means the user typed `clang [tab]` where we should
+  // list all possible flags. If there was no value completion and the user
+  // pressed tab after a space, we should fall back to a file completion.
+  // Printing a newline is to be consistent with what we print at the end of
+  // this function.
+  if (SuggestedCompletions.empty() && HasSpace && !Flags.empty()) {
+    llvm::outs() << '\n';
+    return;
+  }
+
   // When flag ends with '=' and there was no value completion, return empty
   // string and fall back to the file autocompletion.
   if (SuggestedCompletions.empty() && !Cur.endswith("=")) {
     // If the flag is in the form of "--autocomplete=-foo",
     // we were requested to print out all option names that start with "-foo".
     // For example, "--autocomplete=-fsyn" is expanded to "-fsyntax-only".
     SuggestedCompletions = Opts->findByPrefix(Cur, DisableFlags);
 

clang/test/Driver/autocomplete.c

 // STDLIB: libc++
 // STDLIB-NEXT: libstdc++
 // RUN: %clang --autocomplete=-stdlib= | FileCheck %s -check-prefix=STDLIBALL
 // STDLIBALL: libc++
 // STDLIBALL-NEXT: libstdc++
 // STDLIBALL-NEXT: platform
 // RUN: %clang --autocomplete=-meabi,d | FileCheck %s -check-prefix=MEABI
 // MEABI: default
+// RUN: %clang --autocomplete=-meabi, | FileCheck %s -check-prefix=MEABIALL
 // RUN: %clang --autocomplete=-meabi | FileCheck %s -check-prefix=MEABIALL
 // MEABIALL: 4
 // MEABIALL-NEXT: 5
 // MEABIALL-NEXT: default
 // MEABIALL-NEXT: gnu
 // RUN: %clang --autocomplete=-cl-std=,CL2 | FileCheck %s -check-prefix=CLSTD
 // CLSTD: CL2.0
 // RUN: %clang --autocomplete=-cl-std= | FileCheck %s -check-prefix=CLSTDALL

 // RUN: %clang --autocomplete=foo,bar,,,-fno-sanitize-coverage=,f | FileCheck %s -check-prefix=FNOSANICOVER-CORON
 // FNOSANICOVER-CORON: func
 
 // Clang should return empty string when no value completion was found, which will fall back to file autocompletion
 // RUN: %clang --autocomplete=-fmodule-file= | FileCheck %s -check-prefix=MODULE_FILE_EQUAL
 // MODULE_FILE_EQUAL-NOT: -fmodule-file=
 // RUN: %clang --autocomplete=-fmodule-file | FileCheck %s -check-prefix=MODULE_FILE
 // MODULE_FILE: -fmodule-file=
+
+// RUN: %clang --autocomplete=-Qunused-arguments, | FileCheck %s -check-prefix=QUNUSED_COMMA
+// QUNUSED_COMMA-NOT: -Qunused-arguments
+// RUN: %clang --autocomplete=-Qunused-arguments | FileCheck %s -check-prefix=QUNUSED
+// QUNUSED: -Qunused-arguments