Code completion using LSP and clangd

[Pecan]

I have developed a clangd CB plugin client using Language Server Protocol (LSP).

It's working well.
However, it requires clangd version 12 to work even better.

What is the CodeBlocks policy of distributing an executable, say, clangd.exe v12 with the usual CodeBlock distribution.

CodeLite also distributes clangd with its LSP plugin.

Request for Comments.

[oBFusCATed]

Shipping clangd is a windows thing. I don't think we should do it. Just detect the LLVM installation and use it. Or prompt the user to install it.

[oBFusCATed]

What is the purpose of this LSP plugin? Just provide faster error messages?
In my experience implementing a CC plugin with LSP doesn't work well (don't remember the details).

[ollydbg]

Hi, Pecan, good work!

For me, I think distribute a clangd.dll is OK, or we can distribute a separate plugin package(include the plugin and the clangd.dll). Then the user can just download and unpack it.

If I remember correctly, there is an option in CodeLite IDE, which can let user select which clangd.dll it will use.

Do you have a code repo which others can build/test this plugin?

What is the purpose of this LSP plugin? Just provide faster error messages?
In my experience implementing a CC plugin with LSP doesn't work well (don't remember the details).

Using the LSP, I think at least code completion list will be more precise than the native CC.

[Pecan]

Shipping clangd is a windows thing. I don't think we should do it. Just detect the LLVM installation and use it. Or prompt the user to install it.

Just detecting the installation and using its clangd does not work. I've already tried that. The llvm's versions up to version 8 have no reliable clangd for a CB plugin.

The clangd in llvm versions 8 through 11 are so different from  version 12 that the plugin using them would require two separate plugins or spaghetti code to support them.

CB will have to pick some version between 10 through 12 and program towards that.

I've chosen to work with clangd v12. It can reload the compile commands database without having to kill/restart the LSP server when a user opens a new file.

[Pecan]

What is the purpose of this LSP plugin? Just provide faster error messages?
In my experience implementing a CC plugin with LSP doesn't work well (don't remember the details).

Using  LSP "workspace/publishDiagnostics" with clangd is working well for me. I'ts halved my development time. I no longer have to compile the code to find the errors. They're presented to me as I enter the code or save it.

Clangd supports all the LSP calls plus it's own extensions. So far, I've implemented all CB CC's features via LSP calls except the Symbols browser. Though that's possible to do.

LSP/Clangd is primarily focused on the translation unit (TU). But its still possible to provide a bigger picture by asking for workspace symbols. I haven't tried that (yet).

[Pecan]

...<snip>...
If I remember correctly, there is an option in CodeLite IDE, which can let user select which clangd.dll it will use.

Do you have a code repo which others can build/test this plugin?
...<snip>...

CodeLite allows the user to choose the clang to use, but it prioritizes using clangd v10, which it distributes in dir Runtime/lsp.
Later versions of clangd are very independent of llvm/clang. For example clangd v12 can use many llvm/clang versions.

I don't have a repository yet. Things are still very experimental. But I'll work on that.

[oBFusCATed]

For the record the latest version of clang is 11.1. clang/llvm 12 is some night build. This would fail dramatically on linux if you base your development on this version at least until clang/llvm 12 is actually released in the summer.

Clangd supports all the LSP calls plus it's own extensions. So far, I've implemented all CB CC's features via LSP calls except the Symbols browser. Though that's possible to do.

I know that, CC features required changes to the CCManager API last time I've tried to do it. At least if you want to provide good experience.
I don't think implementing the diagnostics in another info pane tab is a good idea, but this requires another CCManager change which would allow in-editor-notifications.

Also I don't know how is using a mix of clang/gcc these days, but it was a problem in the past.
Also I'm not sure if it is a good idea to base your LSP plugin on only one implementation. If you're going to do it name it clangd-lsp.

[Pecan]

For the record the latest version of clang is 11.1. clang/llvm 12 is some night build. This would fail dramatically on linux if you base your development on this version at least until clang/llvm 12 is actually released in the summer.

I know that, CC features required changes to the CCManager API last time I've tried to do it. At least if you want to provide good experience.
I don't think implementing the diagnostics in another info pane tab is a good idea, but this requires another CCManager change which would allow in-editor-notifications.

Also I don't know how is using a mix of clang/gcc these days, but it was a problem in the past.
Also I'm not sure if it is a good idea to base your LSP plugin on only one implementation. If you're going to do it name it clangd-lsp.

In the furture, I'm sure we can generalize to a LSP UI. For the time being, I'm coding a plugin to concentrate learning and experimentation. I'll be happy to name it clangd-lsp. That's a good name.
 
Good to know clangd v12 rc1 may be out in the summer. I don't expect this plugin will be ready to publish any sooner.