[PATCH] D88172: [clangd] Extract common file-caching logic from ConfigProvider.

[Sam McCall via Phabricator via cfe-commits]

sammccall added a comment.

To give a bit of context here: the end-goal here is hot-reload of compile_commands.json. (This covers our *two* top bugs: #192 and #83).

I'm very happy with the hot-reloading of config files (.clangd etc) and I think it's a good fit to generalize.
In particular, config parsing shouldn't be repeated unneccesarily as it has side-effects (diagnostics). Similarly, compile_commands parsing shouldn't be repeated as it's expensive (the file is often huge).
So this is better than other approaches like caching at the FS level.

We could reasonably apply this to .clang-format and .clang-tidy as well. Currently we stat up the directory chain, and then read and parse these every time. It's not very expensive as these are small files, but it's also not free.

In all of these cases, the costs are going to be in eschewing the simple APIs that hide all the IO. For compile_commands.json, we need to extend or stop using the generic compilation-database plugin mechanism. For clang-tidy/format we need to introduce a tree-shaped cache (we have one for CDBs already).


Repository:
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  https://reviews.llvm.org/D88172/new/

https://reviews.llvm.org/D88172