[PATCH] D60316: [clangd] Include insertion: require header guards, drop other heuristics, treat .def like .inc.

[Sam McCall via Phabricator via cfe-commits]

sammccall created this revision.
sammccall added a reviewer: ioeric.
Herald added subscribers: cfe-commits, kadircet, arphaman, jkorous, MaskRay, ilya-biryukov.
Herald added a project: clang.

We do have some reports of include insertion behaving badly in some
codebases. Requiring header guards both makes sense in principle, and is
likely to disable this "nice-to-have" feature in codebases where headers don't
follow the expected pattern.

With this we can drop some other heuristics, such as looking at file
extensions to detect known non-headers - implementation files have no guards.

One wrinkle here is #import - objc headers may not have guards because
they're intended to be used via #import. If the header is the main file
or is #included, we won't collect locations - merge should take care of
this if we see the file #imported somewhere. Seems likely to be OK.

Headers which have a canonicalization (stdlib, IWYU) are exempt from this check.
*.inc files continue to be handled by looking up to the including file.
This patch also adds *.def here - tablegen wants this pattern too.

In terms of code structure, the division between SymbolCollector and
CanonicalIncludes has shifted: SymbolCollector is responsible for more.
This is because SymbolCollector has all the SourceManager/HeaderSearch access
needed for checking for guards, and we interleave these checks with the *.def
checks in a loop (potentially).
We could hand all the info into CanonicalIncludes and put the logic there
if that's preferable.


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D60316

Files:
  clangd/index/CanonicalIncludes.cpp
  clangd/index/CanonicalIncludes.h
  clangd/index/SymbolCollector.cpp
  unittests/clangd/CodeCompleteTests.cpp
  unittests/clangd/FileIndexTests.cpp
  unittests/clangd/SymbolCollectorTests.cpp
  unittests/clangd/TestTU.cpp
  unittests/clangd/TestTU.h

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