Parse compile commands lazily in InterpolatingCompilationDatabase

Summary:
This greatly reduces the time to read 'compile_commands.json'.
For Chromium on my machine it's now 0.7 seconds vs 30 seconds before the
change.

Reviewers: sammccall, jfb

Reviewed By: sammccall

Subscribers: mgrang, jfb, cfe-commits

Differential Revision: https://reviews.llvm.org/D51314

llvm-svn: 340838

1 files changed, 6 insertions, 3 deletions

diff --git a/clang/unittests/Tooling/CompilationDatabaseTest.cpp b/clang/unittests/Tooling/CompilationDatabaseTest.cpp
index ffc1d5b..cbe4d28 100644
--- a/clang/unittests/Tooling/CompilationDatabaseTest.cpp
+++ b/clang/unittests/Tooling/CompilationDatabaseTest.cpp
@@ -707,6 +707,7 @@ TEST_F(InterpolateTest, Nearby) {
 
 TEST_F(InterpolateTest, Language) {
   add("dir/foo.cpp", "-std=c++17");
+  add("dir/bar.c", "");
   add("dir/baz.cee", "-x c");
 
   // .h is ambiguous, so we add explicit language flags
@@ -716,9 +717,11 @@ TEST_F(InterpolateTest, Language) {
   EXPECT_EQ(getCommand("foo.hpp"), "clang -D dir/foo.cpp -std=c++17");
   // respect -x if it's already there.
   EXPECT_EQ(getCommand("baz.h"), "clang -D dir/baz.cee -x c-header");
-  // prefer a worse match with the right language
-  EXPECT_EQ(getCommand("foo.c"), "clang -D dir/baz.cee");
-  Entries.erase(path(StringRef("dir/baz.cee")));
+  // prefer a worse match with the right extension.
+  EXPECT_EQ(getCommand("foo.c"), "clang -D dir/bar.c");
+  // make sure we don't crash on queries with invalid extensions.
+  EXPECT_EQ(getCommand("foo.cce"), "clang -D dir/foo.cpp");
+  Entries.erase(path(StringRef("dir/bar.c")));
   // Now we transfer across languages, so drop -std too.
   EXPECT_EQ(getCommand("foo.c"), "clang -D dir/foo.cpp");
 }