[PATCH] D49267: [clangd] Watch for changes in compile_commands.json

[Simon Marchi via Phabricator via cfe-commits]

simark created this revision.
Herald added subscribers: cfe-commits, jkorous, MaskRay, ioeric, ilya-biryukov.

This patch adds support for watching for changes to
compile_commands.json, and reparsing files if needed.

The watching is done using the "workspace/didChangeWatchedFiles"
notification, so the actual file watching is the frontend's problem.

To keep things simple, we react to any change involving a file called
"compile_commands.json".

The chosen strategy tries to avoid useless reparses.  We don't want to
reparse a file if its compile commands don't change.  So when we get a
change notification, we:

1. Save the compile commands of all open files on the side.
2. Clear everything we know about compilation databases and compilation commands.
3. Query the compile commands again for all open files (which will go read the possibly updated compile commands).  If the commands are different than the saved ones, we reparse the file.

I updated the vscode-clangd extension.  If you don't feel inspired, you
can use this small .cpp to test it:

  #ifdef MACRO
  #warning "MACRO is defined"
  #else
  #warning "MACRO is not defined"
  #endif
  
  int main() {}

and this compile_commands.json:

  [{
    "directory": ".",
    "file": "test.cpp",
    "arguments": ["g++", "-c", "test.cpp", "-DMACRO=2"]
  }]

Adding and removing the "-DMACRO=2" argument, you should see a different


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D49267

Files:
  clangd/ClangdLSPServer.cpp
  clangd/ClangdLSPServer.h
  clangd/GlobalCompilationDatabase.cpp
  clangd/GlobalCompilationDatabase.h
  clangd/ProtocolHandlers.cpp
  clangd/ProtocolHandlers.h
  clangd/clients/clangd-vscode/src/extension.ts

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