[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

1 files changed, 7 insertions, 3 deletions

diff --git a/clang/test/Tooling/auto-detect-from-source.cpp b/clang/test/Tooling/auto-detect-from-source.cpp
index 12a660d585a..e6241a9ec3e 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