assistant: Add /rustdoc slash command (#12453)

This PR adds a `/rustdoc` slash command for retrieving and inserting
rustdoc docs into the Assistant.

Right now the command accepts the crate name as an argument and will
return the top-level docs from `docs.rs`.

Release Notes:

- N/A

crates/assistant/Cargo.toml

@@ -39,6 +39,7 @@ parking_lot.workspace = true
 project.workspace = true
 regex.workspace = true
 rope.workspace = true
+rustdoc_to_markdown.workspace = true
 schemars.workspace = true
 search.workspace = true
 semantic_index.workspace = true

crates/assistant/src/assistant_panel.rs

@@ -1,5 +1,5 @@
 use crate::prompts::{generate_content_prompt, PromptLibrary, PromptManager};
-use crate::slash_command::{search_command, tabs_command};
+use crate::slash_command::{rustdoc_command, search_command, tabs_command};
 use crate::{
     assistant_settings::{AssistantDockPosition, AssistantSettings, ZedDotDevModel},
     codegen::{self, Codegen, CodegenKind},
@@ -210,6 +210,7 @@ impl AssistantPanel {
                     slash_command_registry.register_command(tabs_command::TabsSlashCommand);
                     slash_command_registry.register_command(project_command::ProjectSlashCommand);
                     slash_command_registry.register_command(search_command::SearchSlashCommand);
+                    slash_command_registry.register_command(rustdoc_command::RustdocSlashCommand);
 
                     Self {
                         workspace: workspace_handle,

crates/assistant/src/slash_command.rs

@@ -20,6 +20,7 @@ pub mod active_command;
 pub mod file_command;
 pub mod project_command;
 pub mod prompt_command;
+pub mod rustdoc_command;
 pub mod search_command;
 pub mod tabs_command;
 

crates/assistant/src/slash_command/rustdoc_command.rs

@@ -0,0 +1,137 @@
+use std::sync::atomic::AtomicBool;
+use std::sync::Arc;
+
+use anyhow::{anyhow, bail, Context, Result};
+use assistant_slash_command::{SlashCommand, SlashCommandOutput, SlashCommandOutputSection};
+use futures::AsyncReadExt;
+use gpui::{AppContext, Task, WeakView};
+use http::{AsyncBody, HttpClient, HttpClientWithUrl};
+use language::LspAdapterDelegate;
+use rustdoc_to_markdown::convert_rustdoc_to_markdown;
+use ui::{prelude::*, ButtonLike, ElevationIndex};
+use workspace::Workspace;
+
+pub(crate) struct RustdocSlashCommand;
+
+impl RustdocSlashCommand {
+    async fn build_message(
+        http_client: Arc<HttpClientWithUrl>,
+        crate_name: String,
+    ) -> Result<String> {
+        let mut response = http_client
+            .get(
+                &format!("https://docs.rs/{crate_name}"),
+                AsyncBody::default(),
+                true,
+            )
+            .await?;
+
+        let mut body = Vec::new();
+        response
+            .body_mut()
+            .read_to_end(&mut body)
+            .await
+            .context("error reading docs.rs response body")?;
+
+        if response.status().is_client_error() {
+            let text = String::from_utf8_lossy(body.as_slice());
+            bail!(
+                "status error {}, response: {text:?}",
+                response.status().as_u16()
+            );
+        }
+
+        convert_rustdoc_to_markdown(&body[..])
+    }
+}
+
+impl SlashCommand for RustdocSlashCommand {
+    fn name(&self) -> String {
+        "rustdoc".into()
+    }
+
+    fn description(&self) -> String {
+        "insert the docs for a Rust crate".into()
+    }
+
+    fn tooltip_text(&self) -> String {
+        "insert rustdoc".into()
+    }
+
+    fn requires_argument(&self) -> bool {
+        true
+    }
+
+    fn complete_argument(
+        &self,
+        _query: String,
+        _cancel: Arc<AtomicBool>,
+        _workspace: WeakView<Workspace>,
+        _cx: &mut AppContext,
+    ) -> Task<Result<Vec<String>>> {
+        Task::ready(Ok(Vec::new()))
+    }
+
+    fn run(
+        self: Arc<Self>,
+        argument: Option<&str>,
+        workspace: WeakView<Workspace>,
+        _delegate: Arc<dyn LspAdapterDelegate>,
+        cx: &mut WindowContext,
+    ) -> Task<Result<SlashCommandOutput>> {
+        let Some(argument) = argument else {
+            return Task::ready(Err(anyhow!("missing crate name")));
+        };
+        let Some(workspace) = workspace.upgrade() else {
+            return Task::ready(Err(anyhow!("workspace was dropped")));
+        };
+
+        let http_client = workspace.read(cx).client().http_client();
+        let crate_name = argument.to_string();
+
+        let text = cx.background_executor().spawn({
+            let crate_name = crate_name.clone();
+            async move { Self::build_message(http_client, crate_name).await }
+        });
+
+        let crate_name = SharedString::from(crate_name);
+        cx.foreground_executor().spawn(async move {
+            let text = text.await?;
+            let range = 0..text.len();
+            Ok(SlashCommandOutput {
+                text,
+                sections: vec![SlashCommandOutputSection {
+                    range,
+                    render_placeholder: Arc::new(move |id, unfold, _cx| {
+                        RustdocPlaceholder {
+                            id,
+                            unfold,
+                            crate_name: crate_name.clone(),
+                        }
+                        .into_any_element()
+                    }),
+                }],
+            })
+        })
+    }
+}
+
+#[derive(IntoElement)]
+struct RustdocPlaceholder {
+    pub id: ElementId,
+    pub unfold: Arc<dyn Fn(&mut WindowContext)>,
+    pub crate_name: SharedString,
+}
+
+impl RenderOnce for RustdocPlaceholder {
+    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
+        let unfold = self.unfold;
+
+        ButtonLike::new(self.id)
+            .style(ButtonStyle::Filled)
+            .layer(ElevationIndex::ElevatedSurface)
+            .child(Icon::new(IconName::FileRust))
+            .child(Label::new(format!("rustdoc: {}", self.crate_name)))
+            .on_click(move |_, cx| unfold(cx))
+    }
+}