Add ability to run ESLint (and other non-primary language server) code actions on format (#8496)

This PR does two things to fix
https://github.com/zed-industries/zed/issues/4325:

1. It changes the way `code_actions_on_format` works to send the
possibly configured code actions to _all_ (and not just the primary)
languages servers. That means configured code actions can now be sent to
ESLint, tailwind, ... and other language servers.
2. It enables `codeActionsOnSave` by default for ESLint. That does
**not** mean that by default we will run something on save, but only
that we enable it for ESLint.

Users can then configure their Zed to run the `eslint` code action on
format. Example, for JavaScript:

```json
    {
      "languages": {
        "JavaScript": {
          "code_actions_on_format": {
            "source.fixAll.eslint": true
          }
        },
      }
    }
```

Release Notes:

- Added ability to run ESLint fixes when formatting a buffer. Code
actions configured in
[`code_actions_on_format`](https://zed.dev/docs/configuring-zed#code-actions-on-format)
are now being sent to _all_ language servers connected to a buffer, not
just the primary one. So if a user now sets `"code_actions_on_format": {
"source.fixAll.eslint": true }` in their Zed settings, the
`source.fixAll.eslint` code action will be sent to ESLint, which is not
a primary language server. Since the formatter (prettier, or external
commands, or another language server, ...) still runs, it's important
that these code actions and the formatter don't clash.
([#4325](https://github.com/zed-industries/zed/issues/4325)).

Demo:



https://github.com/zed-industries/zed/assets/1185253/9ef03ad5-1f5c-4d46-b72a-eef611e32f39

crates/languages/src/typescript.rs

@@ -241,6 +241,11 @@ impl LspAdapter for EsLintLspAdapter {
                         .unwrap_or_else(|| workspace_root.as_os_str()),
                 },
                 "problems": {},
+                "codeActionOnSave": {
+                    // We enable this, but without also configuring `code_actions_on_format`
+                    // in the Zed configuration, it doesn't have an effect.
+                    "enable": true,
+                },
                 "experimental": {
                     "useFlatConfig": workspace_root.join("eslint.config.js").is_file(),
                 },

crates/project/src/project.rs

@@ -4129,17 +4129,13 @@ impl Project {
         cx: &mut ModelContext<Project>,
     ) -> Task<anyhow::Result<ProjectTransaction>> {
         if self.is_local() {
-            let mut buffers_with_paths_and_servers = buffers
+            let mut buffers_with_paths = buffers
                 .into_iter()
                 .filter_map(|buffer_handle| {
                     let buffer = buffer_handle.read(cx);
                     let file = File::from_dyn(buffer.file())?;
                     let buffer_abs_path = file.as_local().map(|f| f.abs_path(cx));
-                    let (adapter, server) = self
-                        .primary_language_server_for_buffer(buffer, cx)
-                        .map(|(a, s)| (Some(a.clone()), Some(s.clone())))
-                        .unwrap_or((None, None));
-                    Some((buffer_handle, buffer_abs_path, adapter, server))
+                    Some((buffer_handle, buffer_abs_path))
                 })
                 .collect::<Vec<_>>();
 
@@ -4147,7 +4143,7 @@ impl Project {
                 // Do not allow multiple concurrent formatting requests for the
                 // same buffer.
                 project.update(&mut cx, |this, cx| {
-                    buffers_with_paths_and_servers.retain(|(buffer, _, _, _)| {
+                    buffers_with_paths.retain(|(buffer, _)| {
                         this.buffers_being_formatted
                             .insert(buffer.read(cx).remote_id())
                     });
@@ -4156,10 +4152,10 @@ impl Project {
                 let _cleanup = defer({
                     let this = project.clone();
                     let mut cx = cx.clone();
-                    let buffers = &buffers_with_paths_and_servers;
+                    let buffers = &buffers_with_paths;
                     move || {
                         this.update(&mut cx, |this, cx| {
-                            for (buffer, _, _, _) in buffers {
+                            for (buffer, _) in buffers {
                                 this.buffers_being_formatted
                                     .remove(&buffer.read(cx).remote_id());
                             }
@@ -4169,9 +4165,14 @@ impl Project {
                 });
 
                 let mut project_transaction = ProjectTransaction::default();
-                for (buffer, buffer_abs_path, lsp_adapter, language_server) in
-                    &buffers_with_paths_and_servers
-                {
+                for (buffer, buffer_abs_path) in &buffers_with_paths {
+                    let adapters_and_servers: Vec<_> = project.update(&mut cx, |project, cx| {
+                        project
+                            .language_servers_for_buffer(&buffer.read(cx), cx)
+                            .map(|(adapter, lsp)| (adapter.clone(), lsp.clone()))
+                            .collect()
+                    })?;
+
                     let settings = buffer.update(&mut cx, |buffer, cx| {
                         language_settings(buffer.language(), buffer.file(), cx).clone()
                     })?;
@@ -4202,9 +4203,7 @@ impl Project {
                         buffer.end_transaction(cx)
                     })?;
 
-                    if let (Some(lsp_adapter), Some(language_server)) =
-                        (lsp_adapter, language_server)
-                    {
+                    for (lsp_adapter, language_server) in adapters_and_servers.iter() {
                         // Apply the code actions on
                         let code_actions: Vec<lsp::CodeActionKind> = settings
                             .code_actions_on_format
@@ -4241,6 +4240,7 @@ impl Project {
                                     if edit.changes.is_none() && edit.document_changes.is_none() {
                                         continue;
                                     }
+
                                     let new = Self::deserialize_workspace_edit(
                                         project
                                             .upgrade()
@@ -4284,17 +4284,23 @@ impl Project {
                         }
                     }
 
-                    // Apply language-specific formatting using either a language server
+                    // Apply language-specific formatting using either the primary language server
                     // or external command.
+                    let primary_language_server = adapters_and_servers
+                        .first()
+                        .cloned()
+                        .map(|(_, lsp)| lsp.clone());
+                    let server_and_buffer = primary_language_server
+                        .as_ref()
+                        .zip(buffer_abs_path.as_ref());
+
                     let mut format_operation = None;
                     match (&settings.formatter, &settings.format_on_save) {
                         (_, FormatOnSave::Off) if trigger == FormatTrigger::Save => {}
 
                         (Formatter::LanguageServer, FormatOnSave::On | FormatOnSave::Off)
                         | (_, FormatOnSave::LanguageServer) => {
-                            if let Some((language_server, buffer_abs_path)) =
-                                language_server.as_ref().zip(buffer_abs_path.as_ref())
-                            {
+                            if let Some((language_server, buffer_abs_path)) = server_and_buffer {
                                 format_operation = Some(FormatOperation::Lsp(
                                     Self::format_via_lsp(
                                         &project,
@@ -4338,7 +4344,7 @@ impl Project {
                             {
                                 format_operation = Some(new_operation);
                             } else if let Some((language_server, buffer_abs_path)) =
-                                language_server.as_ref().zip(buffer_abs_path.as_ref())
+                                server_and_buffer
                             {
                                 format_operation = Some(FormatOperation::Lsp(
                                     Self::format_via_lsp(