4 files changed, 89 insertions, 70 deletions

diff --git a/editors/code/src/client.ts b/editors/code/src/client.ts
index 7639ed44b..2e3d4aba2 100644
--- a/editors/code/src/client.ts
+++ b/editors/code/src/client.ts
@@ -10,7 +10,7 @@ export async function createClient(config: Config): Promise<null | lc.LanguageCl
     // It might be a good idea to test if the uri points to a file.
     const workspaceFolderPath = workspace.workspaceFolders?.[0]?.uri.fsPath ?? '.';
 
-    const raLspServerPath = await ensureLanguageServerBinary(config.raLspServerSource);
+    const raLspServerPath = await ensureLanguageServerBinary(config.langServerSource);
     if (!raLspServerPath) return null;
 
     const run: lc.Executable = {
diff --git a/editors/code/src/config.ts b/editors/code/src/config.ts
index aca5dab5a..f216ab461 100644
--- a/editors/code/src/config.ts
+++ b/editors/code/src/config.ts
@@ -1,6 +1,6 @@
 import * as os from "os";
 import * as vscode from 'vscode';
-import { BinarySource, BinarySourceType } from "./installation/interfaces";
+import { BinarySource } from "./installation/interfaces";
 
 const RA_LSP_DEBUG = process.env.__RA_LSP_SERVER_DEBUG;
 
@@ -18,20 +18,7 @@ export interface CargoFeatures {
 }
 
 export class Config {
-    readonly raLspServerGithubArtifactName = {
-        linux: "ra_lsp_server-linux",
-        darwin: "ra_lsp_server-mac",
-        win32: "ra_lsp_server-windows.exe",
-        aix: null,
-        android: null,
-        freebsd: null,
-        openbsd: null,
-        sunos: null,
-        cygwin: null,
-        netbsd: null,
-    }[process.platform];
-
-    raLspServerSource!: null | BinarySource;
+    langServerSource!: null | BinarySource;
 
     highlightingOn = true;
     rainbowHighlightingOn = false;
@@ -72,6 +59,56 @@ export class Config {
         return path;
     }
 
+    /**
+     * Name of the binary artifact for `ra_lsp_server` that is published for
+     * `platform` on GitHub releases. (It is also stored under the same name when
+     * downloaded by the extension).
+     */
+    private static prebuiltLangServerFileName(platform: NodeJS.Platform): null | string {
+        switch (platform) {
+            case "linux":  return "ra_lsp_server-linux";
+            case "darwin": return "ra_lsp_server-mac";
+            case "win32":  return "ra_lsp_server-windows.exe";
+
+            // Users on these platforms yet need to manually build from sources
+            case "aix":
+            case "android":
+            case "freebsd":
+            case "openbsd":
+            case "sunos":
+            case "cygwin":
+            case "netbsd": return null;
+            // The list of platforms is exhaustive see (`NodeJS.Platform` type definition)
+        }
+    }
+
+    private static langServerBinarySource(
+        ctx: vscode.ExtensionContext,
+        config: vscode.WorkspaceConfiguration
+    ): null | BinarySource {
+        const raLspServerPath = RA_LSP_DEBUG ?? config.get<null | string>("raLspServerPath");
+
+        if (raLspServerPath) {
+            return {
+                type: BinarySource.Type.ExplicitPath,
+                path: Config.expandPathResolving(raLspServerPath)
+            };
+        }
+
+        const prebuiltBinaryName = Config.prebuiltLangServerFileName(process.platform);
+
+        return !prebuiltBinaryName ? null : {
+            type: BinarySource.Type.GithubRelease,
+            dir: ctx.globalStoragePath,
+            file: prebuiltBinaryName,
+            repo: {
+                name: "rust-analyzer",
+                owner: "rust-analyzer",
+            }
+        };
+    }
+
+
     // FIXME: revisit the logic for `if (.has(...)) config.get(...)` set default
     // values only in one place (i.e. remove default values from non-readonly members declarations)
     private refresh(ctx: vscode.ExtensionContext) {
@@ -107,27 +144,7 @@ export class Config {
             this.prevEnhancedTyping = this.enableEnhancedTyping;
         }
 
-        {
-            const raLspServerPath = RA_LSP_DEBUG ?? config.get<null | string>("raLspServerPath");
-            if (raLspServerPath) {
-                this.raLspServerSource = {
-                    type: BinarySourceType.ExplicitPath,
-                    path: Config.expandPathResolving(raLspServerPath)
-                };
-            } else if (this.raLspServerGithubArtifactName) {
-                this.raLspServerSource = {
-                    type: BinarySourceType.GithubBinary,
-                    dir: ctx.globalStoragePath,
-                    file: this.raLspServerGithubArtifactName,
-                    repo: {
-                        name: "rust-analyzer",
-                        owner: "rust-analyzer",
-                    }
-                };
-            } else {
-                this.raLspServerSource = null;
-            }
-        }
+        this.langServerSource = Config.langServerBinarySource(ctx, config);
 
         if (config.has('cargo-watch.enable')) {
             this.cargoWatchOptions.enable = config.get<boolean>(
diff --git a/editors/code/src/installation/interfaces.ts b/editors/code/src/installation/interfaces.ts
index 03eac5b79..8039d0b90 100644
--- a/editors/code/src/installation/interfaces.ts
+++ b/editors/code/src/installation/interfaces.ts
@@ -12,42 +12,44 @@ export interface ArtifactMetadata {
 }
 
 /**
- * Type tag for `BinarySource` discriminated union.
- */
-export enum BinarySourceType { ExplicitPath, GithubBinary }
-
-/**
  * Represents the source of a binary artifact which is either specified by the user
  * explicitly, or bundled by this extension from GitHub releases.
  */
-export type BinarySource = ExplicitPathSource | GithubBinarySource;
-
-
-export interface ExplicitPathSource {
-    type: BinarySourceType.ExplicitPath;
+export type BinarySource = BinarySource.ExplicitPath | BinarySource.GithubRelease;
 
+export namespace BinarySource {
     /**
-     * Filesystem path to the binary specified by the user explicitly.
+     * Type tag for `BinarySource` discriminated union.
      */
-    path: string;
-}
+    export const enum Type { ExplicitPath, GithubRelease }
 
-export interface GithubBinarySource {
-    type: BinarySourceType.GithubBinary;
+    export interface ExplicitPath {
+        type: Type.ExplicitPath;
 
-    /**
-     * Repository where the binary is stored.
-     */
-    repo: GithubRepo;
+        /**
+         * Filesystem path to the binary specified by the user explicitly.
+         */
+        path: string;
+    }
 
-    /**
-     * Directory on the filesystem where the bundled binary is stored.
-     */
-    dir: string;
+    export interface GithubRelease {
+        type: Type.GithubRelease;
+
+        /**
+         * Repository where the binary is stored.
+         */
+        repo: GithubRepo;
+
+        /**
+         * Directory on the filesystem where the bundled binary is stored.
+         */
+        dir: string;
+
+        /**
+         * Name of the binary file. It is stored under the same name on GitHub releases
+         * and in local `.dir`.
+         */
+        file: string;
+    }
 
-    /**
-     * Name of the binary file. It is stored under the same name on GitHub releases
-     * and in local `.dir`.
-     */
-    file: string;
 }
diff --git a/editors/code/src/installation/language_server.ts b/editors/code/src/installation/language_server.ts
index b75d3a00a..522d59eb5 100644
--- a/editors/code/src/installation/language_server.ts
+++ b/editors/code/src/installation/language_server.ts
@@ -5,12 +5,12 @@ import * as path from "path";
 import { strict as assert } from "assert";
 import { promises as fs } from "fs";
 
-import { BinarySource, BinarySourceType, GithubBinarySource } from "./interfaces";
+import { BinarySource } from "./interfaces";
 import { fetchLatestArtifactMetadata } from "./fetch_latest_artifact_metadata";
 import { downloadFile } from "./download_file";
 
 export async function downloadLatestLanguageServer(
-    {file: artifactFileName, dir: installationDir, repo}: GithubBinarySource
+    {file: artifactFileName, dir: installationDir, repo}: BinarySource.GithubRelease
 ) {
     const binaryMetadata = await fetchLatestArtifactMetadata(repo, artifactFileName);
 
@@ -67,7 +67,7 @@ export async function ensureLanguageServerBinary(
     }
 
     switch (langServerSource.type) {
-        case BinarySourceType.ExplicitPath: {
+        case BinarySource.Type.ExplicitPath: {
             if (isBinaryAvailable(langServerSource.path)) {
                 return langServerSource.path;
             }
@@ -78,7 +78,7 @@ export async function ensureLanguageServerBinary(
             );
             return null;
         }
-        case BinarySourceType.GithubBinary: {
+        case BinarySource.Type.GithubRelease: {
             const bundledBinaryPath = path.join(langServerSource.dir, langServerSource.file);
 
             if (!isBinaryAvailable(bundledBinaryPath)) {
@@ -106,7 +106,7 @@ export async function ensureLanguageServerBinary(
                 );
 
                 vscode.window.showInformationMessage(
-                    "Rust analyzer language server was successfully installed"
+                    "Rust analyzer language server was successfully installed 🦀"
                 );
             }
             return bundledBinaryPath;