lsp: Retrieve links to documentation for the given symbol (#19233)

Closes #18924 

Release Notes:

- Added an `editor:OpenDocs` action to open links to documentation via
rust-analyzer

crates/editor/src/rust_analyzer_ext.rs

@@ -1,3 +1,5 @@
+use std::{fs, path::Path};
+
 use anyhow::Context as _;
 use gpui::{Context, View, ViewContext, VisualContext, WindowContext};
 use language::Language;
@@ -7,7 +9,7 @@ use text::ToPointUtf16;
 
 use crate::{
     element::register_action, lsp_ext::find_specific_language_server_in_selection, Editor,
-    ExpandMacroRecursively,
+    ExpandMacroRecursively, OpenDocs,
 };
 
 const RUST_ANALYZER_NAME: &str = "rust-analyzer";
@@ -24,6 +26,7 @@ pub fn apply_related_actions(editor: &View<Editor>, cx: &mut WindowContext) {
         .is_some()
     {
         register_action(editor, cx, expand_macro_recursively);
+        register_action(editor, cx, open_docs);
     }
 }
 
@@ -94,3 +97,64 @@ pub fn expand_macro_recursively(
     })
     .detach_and_log_err(cx);
 }
+
+pub fn open_docs(editor: &mut Editor, _: &OpenDocs, cx: &mut ViewContext<'_, Editor>) {
+    if editor.selections.count() == 0 {
+        return;
+    }
+    let Some(project) = &editor.project else {
+        return;
+    };
+    let Some(workspace) = editor.workspace() else {
+        return;
+    };
+
+    let Some((trigger_anchor, _rust_language, server_to_query, buffer)) =
+        find_specific_language_server_in_selection(
+            editor,
+            cx,
+            is_rust_language,
+            RUST_ANALYZER_NAME,
+        )
+    else {
+        return;
+    };
+
+    let project = project.clone();
+    let buffer_snapshot = buffer.read(cx).snapshot();
+    let position = trigger_anchor.text_anchor.to_point_utf16(&buffer_snapshot);
+    let open_docs_task = project.update(cx, |project, cx| {
+        project.request_lsp(
+            buffer,
+            project::LanguageServerToQuery::Other(server_to_query),
+            project::lsp_ext_command::OpenDocs { position },
+            cx,
+        )
+    });
+
+    cx.spawn(|_editor, mut cx| async move {
+        let docs_urls = open_docs_task.await.context("open docs")?;
+        if docs_urls.is_empty() {
+            log::debug!("Empty docs urls for position {position:?}");
+            return Ok(());
+        } else {
+            log::debug!("{:?}", docs_urls);
+        }
+
+        workspace.update(&mut cx, |_workspace, cx| {
+            // Check if the local document exists, otherwise fallback to the online document.
+            // Open with the default browser.
+            if let Some(local_url) = docs_urls.local {
+                if fs::metadata(Path::new(&local_url[8..])).is_ok() {
+                    cx.open_url(&local_url);
+                    return;
+                }
+            }
+
+            if let Some(web_url) = docs_urls.web {
+                cx.open_url(&web_url);
+            }
+        })
+    })
+    .detach_and_log_err(cx);
+}