From 9d3530bd4ebaa7dc02494db440026f87f2bb8bc4 Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall@gmail.com>
Date: Fri, 14 Sep 2018 12:24:09 +0000
Subject: [PATCH] [Tooling] JSONCompilationDatabasePlugin infers compile
 commands for missing files

Summary:
See the existing InterpolatingCompilationDatabase for details on how this works.
We've been using this in clangd for a while, the heuristics seem to work well.

Reviewers: bkramer

Subscribers: ilya-biryukov, ioeric, kadircet, cfe-commits

Differential Revision: https://reviews.llvm.org/D51729

llvm-svn: 342228
---
 clang/lib/Tooling/JSONCompilationDatabase.cpp  |  5 ++++-
 clang/test/Tooling/auto-detect-from-source.cpp | 10 +++++++---
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Tooling/JSONCompilationDatabase.cpp b/clang/lib/Tooling/JSONCompilationDatabase.cpp
index 2fa5fce279d6..b0feaa229c11 100644
--- a/clang/lib/Tooling/JSONCompilationDatabase.cpp
+++ b/clang/lib/Tooling/JSONCompilationDatabase.cpp
@@ -157,13 +157,16 @@ std::vector<std::string> unescapeCommandLine(JSONCommandLineSyntax Syntax,
   return parser.parse();
 }
 
+// This plugin locates a nearby compile_command.json file, and also infers
+// compile commands for files not present in the database.
 class JSONCompilationDatabasePlugin : public CompilationDatabasePlugin {
   std::unique_ptr<CompilationDatabase>
   loadFromDirectory(StringRef Directory, std::string &ErrorMessage) override {
     SmallString<1024> JSONDatabasePath(Directory);
     llvm::sys::path::append(JSONDatabasePath, "compile_commands.json");
-    return JSONCompilationDatabase::loadFromFile(
+    auto Base = JSONCompilationDatabase::loadFromFile(
         JSONDatabasePath, ErrorMessage, JSONCommandLineSyntax::AutoDetect);
+    return Base ? inferMissingCompileCommands(std::move(Base)) : nullptr;
   }
 };
 
diff --git a/clang/test/Tooling/auto-detect-from-source.cpp b/clang/test/Tooling/auto-detect-from-source.cpp
index 12a660d585a9..e6241a9ec3e5 100644
--- a/clang/test/Tooling/auto-detect-from-source.cpp
+++ b/clang/test/Tooling/auto-detect-from-source.cpp
@@ -1,8 +1,12 @@
 // RUN: rm -rf %t
 // RUN: mkdir %t
-// RUN: echo "[{\"directory\":\".\",\"command\":\"clang++ -c %/t/test.cpp\",\"file\":\"%/t/test.cpp\"}]" | sed -e 's/\\/\\\\/g' > %t/compile_commands.json
+// RUN: echo "[{\"directory\":\".\",\"command\":\"clang++ -DSECRET=XYZZY -c %/t/test.cpp\",\"file\":\"%/t/test.cpp\"}]" | sed -e 's/\\/\\\\/g' > %t/compile_commands.json
 // RUN: cp "%s" "%t/test.cpp"
 // RUN: not clang-check "%t/test.cpp" 2>&1 | FileCheck %s
 
-// CHECK: C++ requires
-invalid;
+// CHECK: XYZZY
+SECRET;
+
+// Copy to a different file, and rely on the command being inferred.
+// RUN: cp "%s" "%t/other.cpp"
+// RUN: not clang-check "%t/other.cpp" 2>&1 | FileCheck %s