Add ability to specify binary path/args for rust-analyzer (#9293)

This fixes #9292 by adding a section to the language server settings
that allows users to specify the binary path and arguments with which to
start up a language server.

Example user settings for `rust-analyzer`:

```json
{
  "lsp": {
    "rust-analyzer": {
      "binary": {
        "path": "/Users/thorstenball/tmp/rust-analyzer-aarch64-apple-darwin",
        "arguments": ["--no-log-buffering"]
      }
    }
  }
}
```

Constraints:

* Right now this only allows ABSOLUTE paths.
* This is only used by `rust-analyzer` integration right now, but the
setting can be used for other language servers. We just need to update
the adapters to also respect that setting.



Release Notes:

- Added ability to specify `rust-analyzer` binary `path` (must be
absolute) and `arguments` in user settings. Example: `{"lsp":
{"rust-analyzer": {"binary": {"path": "/my/abs/path/rust-analyzer",
"arguments": ["--no-log-buffering"] }}}}`
([#9292](https://github.com/zed-industries/zed/issues/9292)).

Co-authored-by: Ricard Mallafre <rikitzzz@gmail.com>

crates/languages/src/rust.rs

@@ -2,12 +2,15 @@ use anyhow::{anyhow, bail, Result};
 use async_compression::futures::bufread::GzipDecoder;
 use async_trait::async_trait;
 use futures::{io::BufReader, StreamExt};
+use gpui::AsyncAppContext;
 pub use language::*;
 use lazy_static::lazy_static;
 use lsp::LanguageServerBinary;
+use project::project_settings::ProjectSettings;
 use regex::Regex;
+use settings::Settings;
 use smol::fs::{self, File};
-use std::{any::Any, borrow::Cow, env::consts, path::PathBuf, str, sync::Arc};
+use std::{any::Any, borrow::Cow, env::consts, path::PathBuf, sync::Arc};
 use util::{
     async_maybe,
     fs::remove_matching,
@@ -17,10 +20,41 @@ use util::{
 
 pub struct RustLspAdapter;
 
-#[async_trait]
+impl RustLspAdapter {
+    const SERVER_NAME: &'static str = "rust-analyzer";
+}
+
+#[async_trait(?Send)]
 impl LspAdapter for RustLspAdapter {
     fn name(&self) -> LanguageServerName {
-        LanguageServerName("rust-analyzer".into())
+        LanguageServerName(Self::SERVER_NAME.into())
+    }
+
+    async fn check_if_user_installed(
+        &self,
+        _delegate: &dyn LspAdapterDelegate,
+        cx: &AsyncAppContext,
+    ) -> Option<LanguageServerBinary> {
+        let binary = cx
+            .update(|cx| {
+                ProjectSettings::get_global(cx)
+                    .lsp
+                    .get(Self::SERVER_NAME)
+                    .and_then(|s| s.binary.clone())
+            })
+            .ok()??;
+
+        let path = binary.path?;
+        Some(LanguageServerBinary {
+            path: path.into(),
+            arguments: binary
+                .arguments
+                .unwrap_or_default()
+                .iter()
+                .map(|arg| arg.into())
+                .collect(),
+            env: None,
+        })
     }
 
     async fn fetch_latest_server_version(