Sort the autocomplete candidates before printing them out.

[ruiu]

Summary

Currently, autocompleted options are displayed in the same order as we
wrote them in .td files. This patch sort them out in clang so that they
are sorted alphabetically. This should improve usability.

[yamaguchi]

LGTM! Thanks for the patch.

clang/lib/Driver/Driver.cpp

if (PassedFlags.find(',') == StringRef::npos) {
       // requested to print out all option values for "-foo" that start with
       // "bar". For example,
       // "--autocomplete=-stdlib=,l" is expanded to "libc++" and "libstdc++".
       StringRef Option, Arg;
       std::tie(Option, Arg) = PassedFlags.split(',');
       SuggestedCompletions = Opts->suggestValueCompletions(Option, Arg);
     }
 
+    // Sort the autocomplete candidates so that shells print them out in a
+    // deterministic order. We could sort in any way, but we chose
+    // case-insensitive sorting for consistency with the -help option
+    // which prints out options in the case-insensitive alphabetical order.
+    std::sort(SuggestedCompletions.begin(), SuggestedCompletions.end(),
+              [](StringRef A, StringRef B) { return A.compare_lower(B) < 0; });
+
     llvm::outs() << llvm::join(SuggestedCompletions, " ") << '\n';
     return false;
   }
 
   if (C.getArgs().hasArg(options::OPT_print_libgcc_file_name)) {
     ToolChain::RuntimeLibType RLT = TC.GetRuntimeLibType(C.getArgs());
     switch (RLT) {
     case ToolChain::RLT_CompilerRT:

clang/test/Driver/autocomplete.c

 // RUN: %clang --autocomplete=-fsyn | FileCheck %s -check-prefix=FSYN
 // FSYN: -fsyntax-only
 // RUN: %clang --autocomplete=-s | FileCheck %s -check-prefix=STD
 // STD: -std={{.*}}-stdlib=
 // RUN: %clang --autocomplete=foo | FileCheck %s -check-prefix=FOO
 // FOO-NOT: foo
 // RUN: %clang --autocomplete=-stdlib=,l | FileCheck %s -check-prefix=STDLIB
 // STDLIB: libc++ libstdc++
 // RUN: %clang --autocomplete=-stdlib=, | FileCheck %s -check-prefix=STDLIBALL
 // STDLIBALL: libc++ libstdc++ platform
 // RUN: %clang --autocomplete=-meabi,d | FileCheck %s -check-prefix=MEABI
 // MEABI: default
 // RUN: %clang --autocomplete=-meabi, | FileCheck %s -check-prefix=MEABIALL
-// MEABIALL: default 4 5 gnu
+// MEABIALL: 4 5 default 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
 // CLSTDALL: cl CL cl1.1 CL1.1 cl1.2 CL1.2 cl2.0 CL2.0
 // RUN: %clang --autocomplete=-fno-sanitize-coverage=,f | FileCheck %s -check-prefix=FNOSANICOVER
 // FNOSANICOVER: func
 // RUN: %clang --autocomplete=-fno-sanitize-coverage=, | FileCheck %s -check-prefix=FNOSANICOVERALL
-// FNOSANICOVERALL: func bb edge indirect-calls trace-bb trace-cmp trace-div trace-gep 8bit-counters trace-pc trace-pc-guard no-prune inline-8bit-counters
+// FNOSANICOVERALL: 8bit-counters bb edge func indirect-calls inline-8bit-counters no-prune trace-bb trace-cmp trace-div trace-gep trace-pc trace-pc-guard
 // RUN: %clang --autocomplete=-ffp-contract=, | FileCheck %s -check-prefix=FFPALL
-// FFPALL: fast on off
+// FFPALL: fast off on
 // RUN: %clang --autocomplete=-flto=, | FileCheck %s -check-prefix=FLTOALL
-// FLTOALL: thin full
+// FLTOALL: full thin
 // RUN: %clang --autocomplete=-fveclib=, | FileCheck %s -check-prefix=FVECLIBALL
-// FVECLIBALL: Accelerate SVML none
+// FVECLIBALL: Accelerate none SVML
 // RUN: %clang --autocomplete=-fshow-overloads=, | FileCheck %s -check-prefix=FSOVERALL
-// FSOVERALL: best all
+// FSOVERALL: all best
 // RUN: %clang --autocomplete=-fvisibility=, | FileCheck %s -check-prefix=FVISIBILITYALL
-// FVISIBILITYALL: hidden default
+// FVISIBILITYALL: default hidden
 // RUN: %clang --autocomplete=-mfloat-abi=, | FileCheck %s -check-prefix=MFLOATABIALL
-// MFLOATABIALL: soft softfp hard
+// MFLOATABIALL: hard soft softfp
 // RUN: %clang --autocomplete=-mthread-model, | FileCheck %s -check-prefix=MTHREADMODELALL
 // MTHREADMODELALL: posix single