Gnome Builder support

[lnicola]

It seems that Gnome Builder supports LSP, but doesn't allow users to configure the path to the server. Replacing rls with rust-analyzer in /usr/lib/gnome-builder/plugins/rls_plugin.py should work, but after doing that I ran into a snag.

rust-analyzer starts, but uses the wrong project directory and doesn't work very well. It's worth looking into this as it would improve compatibility with at least one editor. One way to debug it would be to trace the LSP communication and compare Gnome Builder with Code.

[lnicola]

More details: unsurprisingly, I had to open the project folder, not a source code file. That takes care of the wrong root directory. Then:

{"method":"textDocument/didChange","jsonrpc":"2.0","params":{"textDocument":{"uri":"file:///home/user/Projects/hello/src/main.rs","version":20},"contentChanges":[{"range":{"start":{"line":2,"character":5},"end":{"line":2,"character":5}},"rangeLength":0,"text":"."}]}}
{"method":"textDocument/completion","jsonrpc":"2.0","id":30,"params":{"textDocument":{"uri":"file:///home/user/Projects/hello/src/main.rs"},"position":{"line":2,"character":6},"context":{"triggerKind":2}}}

thread '<unnamed>' panicked at 'index out of bounds: the len is 1 but the index is 2', /rustc/38114ff16e7856f98b2b4be7ab4cd29b38bed59a/src/libcore/slice/mod.rs:2842:10
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.45/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.45/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1069
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1427
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:198
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:218
  10: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:511
  11: rust_begin_unwind
             at src/libstd/panicking.rs:419
  12: core::panicking::panic_fmt
             at src/libcore/panicking.rs:111
  13: core::panicking::panic_bounds_check
             at src/libcore/panicking.rs:69
  14: <usize as core::slice::SliceIndex<[T]>>::index
             at /rustc/38114ff16e7856f98b2b4be7ab4cd29b38bed59a/src/libcore/slice/mod.rs:2842
  15: core::slice::<impl core::ops::index::Index<I> for [T]>::index
             at /rustc/38114ff16e7856f98b2b4be7ab4cd29b38bed59a/src/libcore/slice/mod.rs:2707
  16: <alloc::vec::Vec<T> as core::ops::index::Index<I>>::index
             at /rustc/38114ff16e7856f98b2b4be7ab4cd29b38bed59a/src/liballoc/vec.rs:1891
  17: ra_ide_db::line_index::LineIndex::offset
             at crates/ra_ide_db/src/line_index.rs:88
  18: <lsp_types::Position as rust_analyzer::conv::ConvWith<&ra_ide_db::line_index::LineIndex>>::conv_with
             at crates/rust-analyzer/src/conv.rs:184
  19: <&lsp_types::TextDocumentPositionParams as rust_analyzer::conv::TryConvWith<&rust_analyzer::world::WorldSnapshot>>::try_conv_with
             at crates/rust-analyzer/src/conv.rs:440
  20: rust_analyzer::main_loop::handlers::handle_completion
             at crates/rust-analyzer/src/main_loop/handlers.rs:405

The source code is:

fn main() {
    let s = "hello".to_owned();
    s.<|>
    println!("{}", s);
}

[kjeremy]

I can't reproduce this in vscode. In fact in vscode it always seems to send down the entire file in textDocument/didChange. I wonder if that plays into it.

[lnicola]

With Code:

{"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///home/user/Projects/hello/src/main.rs","version":3},"contentChanges":[{"text":"fn main() {\n    let s = \"hello\".to_owned();\n    s.\n    println!(\"{}\", s);\n}\n"}]}}
{"jsonrpc":"2.0","id":14,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:///home/user/Projects/hello/src/main.rs"},"position":{"line":2,"character":6},"context":{"triggerKind":2,"triggerCharacter":"."}}}

[kjeremy]

It doesn't look like the gnome builder lsp client is respecting our text synchronization choice of "full" (see caprs.rs) https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_synchronization

[lnicola]

My guess is that rust-analyzer takes the file contents from the request, so when Builder sends only a partial change we index into the change instead of the full file. Part of the problem is that Builder doesn't support full synchronization.

[gwutz]

Hey all. I will help here. Actually i implement the necessary client functionality to react to the server capabilities and send the full buffer instead just the incremental changes.
But i have still another problem:

21:45:01.9212 jsonrpc-input-stream[    2]:  MESSAGE: <<< {"jsonrpc":"2.0","method":"window/showMessage","params":{"message":"rust-analyzer failed to load workspace: Failed to read Cargo metadata from Cargo.toml file /home/randomDude/Projects/git-project/Cargo.toml: Failed to run `cargo metadata --manifest-path /home/randomDude/Projects/git-project/Cargo.toml`: No such file or directory (os error 2): No such file or directory (os error 2)","type":1}}

Do i have to set some specific environment variables to be able to use rust-analyzer correctly? This file exists of course.

[lnicola]

It sounds like cargo is not on your PATH. That's common with DEs, since it's added the by .bash_profile and that's not sourced if you run the editor from the DE. Try running it from a terminal.

[gwutz]

Got it. Seems to work at least without specific errors. Completion is still not valid - will investigate whats the problem here. Thank you @lnicola

[lnicola]

@gwutz it works fine for me 😛:

[gwutz]

Did you implemented the full text synchronization? I got it already to work too. Right now i make my PoC product ready here: https://gitlab.gnome.org/GNOME/gnome-builder/-/merge_requests/268

[lnicola]

No, I added incremental synchronization support in #4153.

[gwutz]

Ha, this super awesome. What will be the default for the future? Full or incremental? I still will finish this plugin (as there is no implementation for analyzer nevertheless) and maybe i can drive some specific language server client things (messages, installation automatic etc.)
Just want to make sure that gnome-builder is a viable alternative for rust as IDE

[lnicola]

I hope we'll default to incremental, but my PR wasn't even reviewed yet, so don't take it for granted.

[kjeremy]

@lnicola FYI I'm not sure if you've worked on Gnome Builder but it should support all three modes: see microsoft/language-server-protocol#967 (comment)

[gwutz]

@kjeremy yes but this is not the case right now