chore: Extract languages from zed crate (#8270)

- Moves languages module from `zed` into a separate crate. That way we
have less of a long pole at the end of compilation.
- Removes moot dependencies on editor/picker. This is totally harmless
and might help in the future if we decide to decouple picker from
editor.

Before:
```
Number of crates that depend on 'picker' but not on 'editor': 1
Total number of crates that depend on 'picker': 13
Total number of crates that depend on 'editor': 30
```
After:
```
Number of crates that depend on 'picker' but not on 'editor': 5
Total number of crates that depend on 'picker': 12
Total number of crates that depend on 'editor': 26
```
The more crates depend on just picker but not editor, the better in that
case.

Release Notes:

- N/A

crates/languages/src/elm.rs

@@ -0,0 +1,150 @@
+use anyhow::{anyhow, Result};
+use async_trait::async_trait;
+use futures::StreamExt;
+use gpui::AppContext;
+use language::{LanguageServerName, LspAdapter, LspAdapterDelegate};
+use lsp::LanguageServerBinary;
+use node_runtime::NodeRuntime;
+use project::project_settings::ProjectSettings;
+use serde_json::Value;
+use settings::Settings;
+use smol::fs;
+use std::{
+    any::Any,
+    ffi::OsString,
+    path::{Path, PathBuf},
+    sync::Arc,
+};
+use util::ResultExt;
+
+const SERVER_NAME: &'static str = "elm-language-server";
+const SERVER_PATH: &'static str = "node_modules/@elm-tooling/elm-language-server/out/node/index.js";
+
+fn server_binary_arguments(server_path: &Path) -> Vec<OsString> {
+    vec![server_path.into(), "--stdio".into()]
+}
+
+pub struct ElmLspAdapter {
+    node: Arc<dyn NodeRuntime>,
+}
+
+impl ElmLspAdapter {
+    pub fn new(node: Arc<dyn NodeRuntime>) -> Self {
+        ElmLspAdapter { node }
+    }
+}
+
+#[async_trait]
+impl LspAdapter for ElmLspAdapter {
+    fn name(&self) -> LanguageServerName {
+        LanguageServerName(SERVER_NAME.into())
+    }
+
+    fn short_name(&self) -> &'static str {
+        "elmLS"
+    }
+
+    async fn fetch_latest_server_version(
+        &self,
+        _: &dyn LspAdapterDelegate,
+    ) -> Result<Box<dyn 'static + Any + Send>> {
+        Ok(Box::new(
+            self.node
+                .npm_package_latest_version("@elm-tooling/elm-language-server")
+                .await?,
+        ) as Box<_>)
+    }
+
+    async fn fetch_server_binary(
+        &self,
+        version: Box<dyn 'static + Send + Any>,
+        container_dir: PathBuf,
+        _: &dyn LspAdapterDelegate,
+    ) -> Result<LanguageServerBinary> {
+        let version = version.downcast::<String>().unwrap();
+        let server_path = container_dir.join(SERVER_PATH);
+
+        if fs::metadata(&server_path).await.is_err() {
+            self.node
+                .npm_install_packages(
+                    &container_dir,
+                    &[("@elm-tooling/elm-language-server", version.as_str())],
+                )
+                .await?;
+        }
+
+        Ok(LanguageServerBinary {
+            path: self.node.binary_path().await?,
+            env: None,
+            arguments: server_binary_arguments(&server_path),
+        })
+    }
+
+    async fn cached_server_binary(
+        &self,
+        container_dir: PathBuf,
+        _: &dyn LspAdapterDelegate,
+    ) -> Option<LanguageServerBinary> {
+        get_cached_server_binary(container_dir, &*self.node).await
+    }
+
+    async fn installation_test_binary(
+        &self,
+        container_dir: PathBuf,
+    ) -> Option<LanguageServerBinary> {
+        get_cached_server_binary(container_dir, &*self.node).await
+    }
+
+    fn workspace_configuration(&self, _workspace_root: &Path, cx: &mut AppContext) -> Value {
+        // elm-language-server expects workspace didChangeConfiguration notification
+        // params to be the same as lsp initialization_options
+        let override_options = ProjectSettings::get_global(cx)
+            .lsp
+            .get(SERVER_NAME)
+            .and_then(|s| s.initialization_options.clone())
+            .unwrap_or_default();
+
+        match override_options.clone().as_object_mut() {
+            Some(op) => {
+                // elm-language-server requests workspace configuration
+                // for the `elmLS` section, so we have to nest
+                // another copy of initialization_options there
+                op.insert("elmLS".into(), override_options);
+                serde_json::to_value(op).unwrap_or_default()
+            }
+            None => override_options,
+        }
+    }
+}
+
+async fn get_cached_server_binary(
+    container_dir: PathBuf,
+    node: &dyn NodeRuntime,
+) -> Option<LanguageServerBinary> {
+    (|| async move {
+        let mut last_version_dir = None;
+        let mut entries = fs::read_dir(&container_dir).await?;
+        while let Some(entry) = entries.next().await {
+            let entry = entry?;
+            if entry.file_type().await?.is_dir() {
+                last_version_dir = Some(entry.path());
+            }
+        }
+        let last_version_dir = last_version_dir.ok_or_else(|| anyhow!("no cached binary"))?;
+        let server_path = last_version_dir.join(SERVER_PATH);
+        if server_path.exists() {
+            Ok(LanguageServerBinary {
+                path: node.binary_path().await?,
+                env: None,
+                arguments: server_binary_arguments(&server_path),
+            })
+        } else {
+            Err(anyhow!(
+                "missing executable in directory {:?}",
+                last_version_dir
+            ))
+        }
+    })()
+    .await
+    .log_err()
+}