Extract lua language support into an extension (#10437)

Release Notes:

- Extracted lua language support into an extension, and improved Lua
highlighting and completion label styling.

---------

Co-authored-by: Marshall <marshall@zed.dev>

extensions/lua/src/lua.rs

@@ -0,0 +1,158 @@
+use std::fs;
+use zed::lsp::CompletionKind;
+use zed::{CodeLabel, CodeLabelSpan, LanguageServerId};
+use zed_extension_api::{self as zed, Result};
+
+struct LuaExtension {
+    cached_binary_path: Option<String>,
+}
+
+impl LuaExtension {
+    fn language_server_binary_path(
+        &mut self,
+        language_server_id: &LanguageServerId,
+        worktree: &zed::Worktree,
+    ) -> Result<String> {
+        if let Some(path) = &self.cached_binary_path {
+            if fs::metadata(path).map_or(false, |stat| stat.is_file()) {
+                return Ok(path.clone());
+            }
+        }
+
+        if let Some(path) = worktree.which("lua-language-server") {
+            self.cached_binary_path = Some(path.clone());
+            return Ok(path);
+        }
+
+        zed::set_language_server_installation_status(
+            &language_server_id,
+            &zed::LanguageServerInstallationStatus::CheckingForUpdate,
+        );
+        let release = zed::latest_github_release(
+            "LuaLS/lua-language-server",
+            zed::GithubReleaseOptions {
+                require_assets: true,
+                pre_release: false,
+            },
+        )?;
+
+        let (platform, arch) = zed::current_platform();
+        let asset_name = format!(
+            "lua-language-server-{version}-{os}-{arch}.tar.gz",
+            version = release.version,
+            os = match platform {
+                zed::Os::Mac => "darwin",
+                zed::Os::Linux => "linux",
+                zed::Os::Windows => "win32",
+            },
+            arch = match arch {
+                zed::Architecture::Aarch64 => "arm64",
+                zed::Architecture::X8664 => "x86_64",
+                zed::Architecture::X86 => return Err("unsupported platform x86".into()),
+            },
+        );
+
+        let asset = release
+            .assets
+            .iter()
+            .find(|asset| asset.name == asset_name)
+            .ok_or_else(|| format!("no asset found matching {:?}", asset_name))?;
+
+        let version_dir = format!("lua-language-server-{}", release.version);
+        let binary_path = format!("{version_dir}/bin/lua-language-server");
+
+        if !fs::metadata(&binary_path).map_or(false, |stat| stat.is_file()) {
+            zed::set_language_server_installation_status(
+                &language_server_id,
+                &zed::LanguageServerInstallationStatus::Downloading,
+            );
+
+            zed::download_file(
+                &asset.download_url,
+                &version_dir,
+                zed::DownloadedFileType::GzipTar,
+            )
+            .map_err(|e| format!("failed to download file: {e}"))?;
+
+            let entries =
+                fs::read_dir(".").map_err(|e| format!("failed to list working directory {e}"))?;
+            for entry in entries {
+                let entry = entry.map_err(|e| format!("failed to load directory entry {e}"))?;
+                if entry.file_name().to_str() != Some(&version_dir) {
+                    fs::remove_dir_all(&entry.path()).ok();
+                }
+            }
+        }
+
+        self.cached_binary_path = Some(binary_path.clone());
+        Ok(binary_path)
+    }
+}
+
+impl zed::Extension for LuaExtension {
+    fn new() -> Self {
+        Self {
+            cached_binary_path: None,
+        }
+    }
+
+    fn language_server_command(
+        &mut self,
+        language_server_id: &LanguageServerId,
+        worktree: &zed::Worktree,
+    ) -> Result<zed::Command> {
+        Ok(zed::Command {
+            command: self.language_server_binary_path(language_server_id, worktree)?,
+            args: Default::default(),
+            env: Default::default(),
+        })
+    }
+
+    fn label_for_completion(
+        &self,
+        _language_server_id: &LanguageServerId,
+        completion: zed::lsp::Completion,
+    ) -> Option<CodeLabel> {
+        match completion.kind? {
+            CompletionKind::Method | CompletionKind::Function => {
+                let name_len = completion.label.find('(').unwrap_or(completion.label.len());
+                Some(CodeLabel {
+                    spans: vec![CodeLabelSpan::code_range(0..completion.label.len())],
+                    filter_range: (0..name_len).into(),
+                    code: completion.label,
+                })
+            }
+            CompletionKind::Field => Some(CodeLabel {
+                spans: vec![CodeLabelSpan::literal(
+                    completion.label.clone(),
+                    Some("property".into()),
+                )],
+                filter_range: (0..completion.label.len()).into(),
+                code: Default::default(),
+            }),
+            _ => None,
+        }
+    }
+
+    fn label_for_symbol(
+        &self,
+        _language_server_id: &LanguageServerId,
+        symbol: zed::lsp::Symbol,
+    ) -> Option<CodeLabel> {
+        let prefix = "let a = ";
+        let suffix = match symbol.kind {
+            zed::lsp::SymbolKind::Method => "()",
+            _ => "",
+        };
+        let code = format!("{prefix}{}{suffix}", symbol.name);
+        Some(CodeLabel {
+            spans: vec![CodeLabelSpan::code_range(
+                prefix.len()..code.len() - suffix.len(),
+            )],
+            filter_range: (0..symbol.name.len()).into(),
+            code,
+        })
+    }
+}
+
+zed::register_extension!(LuaExtension);