lsp: Implement support for the textDocument/diagnostic command (#19230)

Closes [#13107](https://github.com/zed-industries/zed/issues/13107)

Enabled pull diagnostics by default, for the language servers that
declare support in the corresponding capabilities.

```
"diagnostics": {
    "lsp_pull_diagnostics_debounce_ms": null
}
```
settings can be used to disable the pulling.

Release Notes:

- Added support for the LSP `textDocument/diagnostic` command.

# Brief

This is draft PR that implements the LSP `textDocument/diagnostic`
command. The goal is to receive your feedback and establish further
steps towards fully implementing this command. I tried to re-use
existing method and structures to ensure:

1. The existing functionality works as before
2. There is no interference between the diagnostics sent by a server and
the diagnostics requested by a client.

The current implementation is done via a new LSP command
`GetDocumentDiagnostics` that is sent when a buffer is saved and when a
buffer is edited. There is a new method called `pull_diagnostic` that is
called for such events. It has debounce to ensure we don't spam a server
with commands every time the buffer is edited. Probably, we don't need
the debounce when the buffer is saved.

All in all, the goal is basically to get your feedback and ensure I am
on the right track. Thanks!


## References

1.
https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_pullDiagnostics

## In action

You can clone any Ruby repo since the `ruby-lsp` supports the pull
diagnostics only.

Steps to reproduce:

1. Clone this repo https://github.com/vitallium/stimulus-lsp-error-zed
2. Install Ruby (via `asdf` or `mise).
4. Install Ruby gems via `bundle install`
5. Install Ruby LSP with `gem install ruby-lsp`
6. Check out this PR and build Zed
7. Open any file and start editing to see diagnostics in realtime.



https://github.com/user-attachments/assets/0ef6ec41-e4fa-4539-8f2c-6be0d8be4129

---------

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>

crates/language/src/buffer.rs

@@ -229,12 +229,21 @@ pub struct Diagnostic {
     pub is_disk_based: bool,
     /// Whether this diagnostic marks unnecessary code.
     pub is_unnecessary: bool,
+    /// Quick separation of diagnostics groups based by their source.
+    pub source_kind: DiagnosticSourceKind,
     /// Data from language server that produced this diagnostic. Passed back to the LS when we request code actions for this diagnostic.
     pub data: Option<Value>,
     /// Whether to underline the corresponding text range in the editor.
     pub underline: bool,
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub enum DiagnosticSourceKind {
+    Pulled,
+    Pushed,
+    Other,
+}
+
 /// An operation used to synchronize this buffer with its other replicas.
 #[derive(Clone, Debug, PartialEq)]
 pub enum Operation {
@@ -4636,6 +4645,7 @@ impl Default for Diagnostic {
     fn default() -> Self {
         Self {
             source: Default::default(),
+            source_kind: DiagnosticSourceKind::Other,
             code: None,
             code_description: None,
             severity: DiagnosticSeverity::ERROR,

crates/language/src/proto.rs

@@ -1,6 +1,6 @@
 //! Handles conversions of `language` items to and from the [`rpc`] protocol.
 
-use crate::{CursorShape, Diagnostic, diagnostic_set::DiagnosticEntry};
+use crate::{CursorShape, Diagnostic, DiagnosticSourceKind, diagnostic_set::DiagnosticEntry};
 use anyhow::{Context as _, Result};
 use clock::ReplicaId;
 use lsp::{DiagnosticSeverity, LanguageServerId};
@@ -200,6 +200,11 @@ pub fn serialize_diagnostics<'a>(
         .into_iter()
         .map(|entry| proto::Diagnostic {
             source: entry.diagnostic.source.clone(),
+            source_kind: match entry.diagnostic.source_kind {
+                DiagnosticSourceKind::Pulled => proto::diagnostic::SourceKind::Pulled,
+                DiagnosticSourceKind::Pushed => proto::diagnostic::SourceKind::Pushed,
+                DiagnosticSourceKind::Other => proto::diagnostic::SourceKind::Other,
+            } as i32,
             start: Some(serialize_anchor(&entry.range.start)),
             end: Some(serialize_anchor(&entry.range.end)),
             message: entry.diagnostic.message.clone(),
@@ -431,6 +436,13 @@ pub fn deserialize_diagnostics(
                     is_disk_based: diagnostic.is_disk_based,
                     is_unnecessary: diagnostic.is_unnecessary,
                     underline: diagnostic.underline,
+                    source_kind: match proto::diagnostic::SourceKind::from_i32(
+                        diagnostic.source_kind,
+                    )? {
+                        proto::diagnostic::SourceKind::Pulled => DiagnosticSourceKind::Pulled,
+                        proto::diagnostic::SourceKind::Pushed => DiagnosticSourceKind::Pushed,
+                        proto::diagnostic::SourceKind::Other => DiagnosticSourceKind::Other,
+                    },
                     data,
                 },
             })