lsp: Add support for clangd's inactiveRegions extension (#26146)

Closes #13089 

Here we use `experimental` to advertise our support for
`inactiveRegions`. Note that clangd does not currently have a stable
release that reads the `experimental` object (PR
https://github.com/llvm/llvm-project/pull/116531), this can be tested
with one of clangd's recent "unstable snapshots" in their
[releases](https://github.com/clangd/clangd/releases).

Release Notes:

- Added support for clangd's `inactiveRegions` extension.

![Screen Recording 2025-03-05 at 22 39
58](https://github.com/user-attachments/assets/ceade8bd-4d8e-43c3-9520-ad44efa50d2f)

---------

Co-authored-by: Peter Tripp <peter@zed.dev>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>

crates/project/src/lsp_store/lsp_ext_command.rs

@@ -0,0 +1,365 @@
+use crate::{lsp_command::LspCommand, lsp_store::LspStore, make_text_document_identifier};
+use anyhow::{Context as _, Result};
+use async_trait::async_trait;
+use gpui::{App, AsyncApp, Entity};
+use language::{point_to_lsp, proto::deserialize_anchor, Buffer};
+use lsp::{LanguageServer, LanguageServerId};
+use rpc::proto::{self, PeerId};
+use serde::{Deserialize, Serialize};
+use std::{path::Path, sync::Arc};
+use text::{BufferId, PointUtf16, ToPointUtf16};
+
+pub enum LspExpandMacro {}
+
+impl lsp::request::Request for LspExpandMacro {
+    type Params = ExpandMacroParams;
+    type Result = Option<ExpandedMacro>;
+    const METHOD: &'static str = "rust-analyzer/expandMacro";
+}
+
+#[derive(Deserialize, Serialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct ExpandMacroParams {
+    pub text_document: lsp::TextDocumentIdentifier,
+    pub position: lsp::Position,
+}
+
+#[derive(Default, Deserialize, Serialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct ExpandedMacro {
+    pub name: String,
+    pub expansion: String,
+}
+
+impl ExpandedMacro {
+    pub fn is_empty(&self) -> bool {
+        self.name.is_empty() && self.expansion.is_empty()
+    }
+}
+#[derive(Debug)]
+pub struct ExpandMacro {
+    pub position: PointUtf16,
+}
+
+#[async_trait(?Send)]
+impl LspCommand for ExpandMacro {
+    type Response = ExpandedMacro;
+    type LspRequest = LspExpandMacro;
+    type ProtoRequest = proto::LspExtExpandMacro;
+
+    fn display_name(&self) -> &str {
+        "Expand macro"
+    }
+
+    fn to_lsp(
+        &self,
+        path: &Path,
+        _: &Buffer,
+        _: &Arc<LanguageServer>,
+        _: &App,
+    ) -> Result<ExpandMacroParams> {
+        Ok(ExpandMacroParams {
+            text_document: make_text_document_identifier(path)?,
+            position: point_to_lsp(self.position),
+        })
+    }
+
+    async fn response_from_lsp(
+        self,
+        message: Option<ExpandedMacro>,
+        _: Entity<LspStore>,
+        _: Entity<Buffer>,
+        _: LanguageServerId,
+        _: AsyncApp,
+    ) -> anyhow::Result<ExpandedMacro> {
+        Ok(message
+            .map(|message| ExpandedMacro {
+                name: message.name,
+                expansion: message.expansion,
+            })
+            .unwrap_or_default())
+    }
+
+    fn to_proto(&self, project_id: u64, buffer: &Buffer) -> proto::LspExtExpandMacro {
+        proto::LspExtExpandMacro {
+            project_id,
+            buffer_id: buffer.remote_id().into(),
+            position: Some(language::proto::serialize_anchor(
+                &buffer.anchor_before(self.position),
+            )),
+        }
+    }
+
+    async fn from_proto(
+        message: Self::ProtoRequest,
+        _: Entity<LspStore>,
+        buffer: Entity<Buffer>,
+        mut cx: AsyncApp,
+    ) -> anyhow::Result<Self> {
+        let position = message
+            .position
+            .and_then(deserialize_anchor)
+            .context("invalid position")?;
+        Ok(Self {
+            position: buffer.update(&mut cx, |buffer, _| position.to_point_utf16(buffer))?,
+        })
+    }
+
+    fn response_to_proto(
+        response: ExpandedMacro,
+        _: &mut LspStore,
+        _: PeerId,
+        _: &clock::Global,
+        _: &mut App,
+    ) -> proto::LspExtExpandMacroResponse {
+        proto::LspExtExpandMacroResponse {
+            name: response.name,
+            expansion: response.expansion,
+        }
+    }
+
+    async fn response_from_proto(
+        self,
+        message: proto::LspExtExpandMacroResponse,
+        _: Entity<LspStore>,
+        _: Entity<Buffer>,
+        _: AsyncApp,
+    ) -> anyhow::Result<ExpandedMacro> {
+        Ok(ExpandedMacro {
+            name: message.name,
+            expansion: message.expansion,
+        })
+    }
+
+    fn buffer_id_from_proto(message: &proto::LspExtExpandMacro) -> Result<BufferId> {
+        BufferId::new(message.buffer_id)
+    }
+}
+
+pub enum LspOpenDocs {}
+
+impl lsp::request::Request for LspOpenDocs {
+    type Params = OpenDocsParams;
+    type Result = Option<DocsUrls>;
+    const METHOD: &'static str = "experimental/externalDocs";
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct OpenDocsParams {
+    pub text_document: lsp::TextDocumentIdentifier,
+    pub position: lsp::Position,
+}
+
+#[derive(Serialize, Deserialize, Debug, Default)]
+#[serde(rename_all = "camelCase")]
+pub struct DocsUrls {
+    pub web: Option<String>,
+    pub local: Option<String>,
+}
+
+impl DocsUrls {
+    pub fn is_empty(&self) -> bool {
+        self.web.is_none() && self.local.is_none()
+    }
+}
+
+#[derive(Debug)]
+pub struct OpenDocs {
+    pub position: PointUtf16,
+}
+
+#[async_trait(?Send)]
+impl LspCommand for OpenDocs {
+    type Response = DocsUrls;
+    type LspRequest = LspOpenDocs;
+    type ProtoRequest = proto::LspExtOpenDocs;
+
+    fn display_name(&self) -> &str {
+        "Open docs"
+    }
+
+    fn to_lsp(
+        &self,
+        path: &Path,
+        _: &Buffer,
+        _: &Arc<LanguageServer>,
+        _: &App,
+    ) -> Result<OpenDocsParams> {
+        Ok(OpenDocsParams {
+            text_document: lsp::TextDocumentIdentifier {
+                uri: lsp::Url::from_file_path(path).unwrap(),
+            },
+            position: point_to_lsp(self.position),
+        })
+    }
+
+    async fn response_from_lsp(
+        self,
+        message: Option<DocsUrls>,
+        _: Entity<LspStore>,
+        _: Entity<Buffer>,
+        _: LanguageServerId,
+        _: AsyncApp,
+    ) -> anyhow::Result<DocsUrls> {
+        Ok(message
+            .map(|message| DocsUrls {
+                web: message.web,
+                local: message.local,
+            })
+            .unwrap_or_default())
+    }
+
+    fn to_proto(&self, project_id: u64, buffer: &Buffer) -> proto::LspExtOpenDocs {
+        proto::LspExtOpenDocs {
+            project_id,
+            buffer_id: buffer.remote_id().into(),
+            position: Some(language::proto::serialize_anchor(
+                &buffer.anchor_before(self.position),
+            )),
+        }
+    }
+
+    async fn from_proto(
+        message: Self::ProtoRequest,
+        _: Entity<LspStore>,
+        buffer: Entity<Buffer>,
+        mut cx: AsyncApp,
+    ) -> anyhow::Result<Self> {
+        let position = message
+            .position
+            .and_then(deserialize_anchor)
+            .context("invalid position")?;
+        Ok(Self {
+            position: buffer.update(&mut cx, |buffer, _| position.to_point_utf16(buffer))?,
+        })
+    }
+
+    fn response_to_proto(
+        response: DocsUrls,
+        _: &mut LspStore,
+        _: PeerId,
+        _: &clock::Global,
+        _: &mut App,
+    ) -> proto::LspExtOpenDocsResponse {
+        proto::LspExtOpenDocsResponse {
+            web: response.web,
+            local: response.local,
+        }
+    }
+
+    async fn response_from_proto(
+        self,
+        message: proto::LspExtOpenDocsResponse,
+        _: Entity<LspStore>,
+        _: Entity<Buffer>,
+        _: AsyncApp,
+    ) -> anyhow::Result<DocsUrls> {
+        Ok(DocsUrls {
+            web: message.web,
+            local: message.local,
+        })
+    }
+
+    fn buffer_id_from_proto(message: &proto::LspExtOpenDocs) -> Result<BufferId> {
+        BufferId::new(message.buffer_id)
+    }
+}
+
+pub enum LspSwitchSourceHeader {}
+
+impl lsp::request::Request for LspSwitchSourceHeader {
+    type Params = SwitchSourceHeaderParams;
+    type Result = Option<SwitchSourceHeaderResult>;
+    const METHOD: &'static str = "textDocument/switchSourceHeader";
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct SwitchSourceHeaderParams(lsp::TextDocumentIdentifier);
+
+#[derive(Serialize, Deserialize, Debug, Default)]
+#[serde(rename_all = "camelCase")]
+pub struct SwitchSourceHeaderResult(pub String);
+
+#[derive(Default, Deserialize, Serialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct SwitchSourceHeader;
+
+#[async_trait(?Send)]
+impl LspCommand for SwitchSourceHeader {
+    type Response = SwitchSourceHeaderResult;
+    type LspRequest = LspSwitchSourceHeader;
+    type ProtoRequest = proto::LspExtSwitchSourceHeader;
+
+    fn display_name(&self) -> &str {
+        "Switch source header"
+    }
+
+    fn to_lsp(
+        &self,
+        path: &Path,
+        _: &Buffer,
+        _: &Arc<LanguageServer>,
+        _: &App,
+    ) -> Result<SwitchSourceHeaderParams> {
+        Ok(SwitchSourceHeaderParams(make_text_document_identifier(
+            path,
+        )?))
+    }
+
+    async fn response_from_lsp(
+        self,
+        message: Option<SwitchSourceHeaderResult>,
+        _: Entity<LspStore>,
+        _: Entity<Buffer>,
+        _: LanguageServerId,
+        _: AsyncApp,
+    ) -> anyhow::Result<SwitchSourceHeaderResult> {
+        Ok(message
+            .map(|message| SwitchSourceHeaderResult(message.0))
+            .unwrap_or_default())
+    }
+
+    fn to_proto(&self, project_id: u64, buffer: &Buffer) -> proto::LspExtSwitchSourceHeader {
+        proto::LspExtSwitchSourceHeader {
+            project_id,
+            buffer_id: buffer.remote_id().into(),
+        }
+    }
+
+    async fn from_proto(
+        _: Self::ProtoRequest,
+        _: Entity<LspStore>,
+        _: Entity<Buffer>,
+        _: AsyncApp,
+    ) -> anyhow::Result<Self> {
+        Ok(Self {})
+    }
+
+    fn response_to_proto(
+        response: SwitchSourceHeaderResult,
+        _: &mut LspStore,
+        _: PeerId,
+        _: &clock::Global,
+        _: &mut App,
+    ) -> proto::LspExtSwitchSourceHeaderResponse {
+        proto::LspExtSwitchSourceHeaderResponse {
+            target_file: response.0,
+        }
+    }
+
+    async fn response_from_proto(
+        self,
+        message: proto::LspExtSwitchSourceHeaderResponse,
+        _: Entity<LspStore>,
+        _: Entity<Buffer>,
+        _: AsyncApp,
+    ) -> anyhow::Result<SwitchSourceHeaderResult> {
+        Ok(SwitchSourceHeaderResult(message.target_file))
+    }
+
+    fn buffer_id_from_proto(message: &proto::LspExtSwitchSourceHeader) -> Result<BufferId> {
+        BufferId::new(message.buffer_id)
+    }
+}