7 files changed, 175 insertions, 103 deletions

diff --git a/editors/code/src/client.ts b/editors/code/src/client.ts
index 12c97be2f..efef820ab 100644
--- a/editors/code/src/client.ts
+++ b/editors/code/src/client.ts
@@ -11,7 +11,7 @@ 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 = vscode.workspace.workspaceFolders?.[0]?.uri.fsPath ?? '.';
 
-    const serverPath = await ensureServerBinary(config.serverBinarySource);
+    const serverPath = await ensureServerBinary(config.serverSource);
     if (!serverPath) return null;
 
     const run: lc.Executable = {
diff --git a/editors/code/src/config.ts b/editors/code/src/config.ts
index 8c033052b..70cb0a612 100644
--- a/editors/code/src/config.ts
+++ b/editors/code/src/config.ts
@@ -24,6 +24,19 @@ export class Config {
     ]
     .map(opt => `${Config.rootSection}.${opt}`);
 
+    private static readonly extensionVersion: string = (() => {
+        const packageJsonVersion = vscode
+            .extensions
+            .getExtension("matklad.rust-analyzer")!
+            .packageJSON
+            .version as string; // n.n.YYYYMMDD
+
+        const realVersionRegexp = /^\d+\.\d+\.(\d{4})(\d{2})(\d{2})/;
+        const [, yyyy, mm, dd] = packageJsonVersion.match(realVersionRegexp)!;
+
+        return `${yyyy}-${mm}-${dd}`;
+    })();
+
     private cfg!: vscode.WorkspaceConfiguration;
 
     constructor(private readonly ctx: vscode.ExtensionContext) {
@@ -98,7 +111,7 @@ export class Config {
         }
     }
 
-    get serverBinarySource(): null | BinarySource {
+    get serverSource(): null | BinarySource {
         const serverPath = RA_LSP_DEBUG ?? this.cfg.get<null | string>("raLspServerPath");
 
         if (serverPath) {
@@ -116,6 +129,8 @@ export class Config {
             type: BinarySource.Type.GithubRelease,
             dir:  this.ctx.globalStoragePath,
             file: prebuiltBinaryName,
+            storage: this.ctx.globalState,
+            version: Config.extensionVersion,
             repo: {
                 name: "rust-analyzer",
                 owner: "rust-analyzer",
diff --git a/editors/code/src/ctx.ts b/editors/code/src/ctx.ts
index 70042a479..9fcf2ec38 100644
--- a/editors/code/src/ctx.ts
+++ b/editors/code/src/ctx.ts
@@ -60,6 +60,10 @@ export class Ctx {
         this.pushCleanup(d);
     }
 
+    get globalState(): vscode.Memento {
+        return this.extCtx.globalState;
+    }
+
     get subscriptions(): Disposable[] {
         return this.extCtx.subscriptions;
     }
diff --git a/editors/code/src/installation/download_artifact.ts b/editors/code/src/installation/download_artifact.ts
new file mode 100644
index 000000000..de655f8f4
--- /dev/null
+++ b/editors/code/src/installation/download_artifact.ts
@@ -0,0 +1,58 @@
+import * as vscode from "vscode";
+import * as path from "path";
+import { promises as fs } from "fs";
+import { strict as assert } from "assert";
+
+import { ArtifactReleaseInfo } from "./interfaces";
+import { downloadFile } from "./download_file";
+import { throttle } from "throttle-debounce";
+
+/**
+ * Downloads artifact from given `downloadUrl`.
+ * Creates `installationDir` if it is not yet created and put the artifact under
+ * `artifactFileName`.
+ * Displays info about the download progress in an info message printing the name
+ * of the artifact as `displayName`.
+ */
+export async function downloadArtifact(
+    {downloadUrl, releaseName}: ArtifactReleaseInfo,
+    artifactFileName: string,
+    installationDir: string,
+    displayName: string,
+) {
+    await fs.mkdir(installationDir).catch(err => assert.strictEqual(
+        err?.code,
+        "EEXIST",
+        `Couldn't create directory "${installationDir}" to download `+
+        `${artifactFileName} artifact: ${err.message}`
+    ));
+
+    const installationPath = path.join(installationDir, artifactFileName);
+
+    console.time(`Downloading ${artifactFileName}`);
+    await vscode.window.withProgress(
+        {
+            location: vscode.ProgressLocation.Notification,
+            cancellable: false, // FIXME: add support for canceling download?
+            title: `Downloading ${displayName} (${releaseName})`
+        },
+        async (progress, _cancellationToken) => {
+            let lastPrecentage = 0;
+            const filePermissions = 0o755; // (rwx, r_x, r_x)
+            await downloadFile(downloadUrl, installationPath, filePermissions, throttle(
+                200,
+                /* noTrailing: */ true,
+                (readBytes, totalBytes) => {
+                    const newPercentage = (readBytes / totalBytes) * 100;
+                    progress.report({
+                        message: newPercentage.toFixed(0) + "%",
+                        increment: newPercentage - lastPrecentage
+                    });
+
+                    lastPrecentage = newPercentage;
+                })
+            );
+        }
+    );
+    console.timeEnd(`Downloading ${artifactFileName}`);
+}
diff --git a/editors/code/src/installation/fetch_latest_artifact_release_info.ts b/editors/code/src/installation/fetch_artifact_release_info.ts
index 29ee029a7..7d497057a 100644
--- a/editors/code/src/installation/fetch_latest_artifact_release_info.ts
+++ b/editors/code/src/installation/fetch_artifact_release_info.ts
@@ -3,24 +3,30 @@ import { GithubRepo, ArtifactReleaseInfo } from "./interfaces";
 
 const GITHUB_API_ENDPOINT_URL = "https://api.github.com";
 
+
 /**
- * Fetches the latest release from GitHub `repo` and returns metadata about
- * `artifactFileName` shipped with this release or `null` if no such artifact was published.
+ * Fetches the release with `releaseTag` (or just latest release when not specified)
+ * from GitHub `repo` and returns metadata about `artifactFileName` shipped with
+ * this release or `null` if no such artifact was published.
  */
-export async function fetchLatestArtifactReleaseInfo(
-    repo: GithubRepo, artifactFileName: string
+export async function fetchArtifactReleaseInfo(
+    repo: GithubRepo, artifactFileName: string, releaseTag?: string
 ): Promise<null | ArtifactReleaseInfo> {
 
     const repoOwner = encodeURIComponent(repo.owner);
     const repoName  = encodeURIComponent(repo.name);
 
-    const apiEndpointPath = `/repos/${repoOwner}/${repoName}/releases/latest`;
+    const apiEndpointPath = releaseTag
+        ? `/repos/${repoOwner}/${repoName}/releases/tags/${releaseTag}`
+        : `/repos/${repoOwner}/${repoName}/releases/latest`;
+
     const requestUrl = GITHUB_API_ENDPOINT_URL + apiEndpointPath;
 
     // We skip runtime type checks for simplicity (here we cast from `any` to `GithubRelease`)
 
     console.log("Issuing request for released artifacts metadata to", requestUrl);
 
+    // FIXME: handle non-ok response
     const response: GithubRelease = await fetch(requestUrl, {
             headers: { Accept: "application/vnd.github.v3+json" }
         })
diff --git a/editors/code/src/installation/interfaces.ts b/editors/code/src/installation/interfaces.ts
index 93ea577d4..e40839e4b 100644
--- a/editors/code/src/installation/interfaces.ts
+++ b/editors/code/src/installation/interfaces.ts
@@ -1,3 +1,5 @@
+import * as vscode from "vscode";
+
 export interface GithubRepo {
     name: string;
     owner: string;
@@ -50,6 +52,17 @@ export namespace BinarySource {
          * and in local `.dir`.
          */
         file: string;
+
+        /**
+         * Tag of github release that denotes a version required by this extension.
+         */
+        version: string;
+
+        /**
+         * Object that provides `get()/update()` operations to store metadata
+         * about the actual binary, e.g. its actual version.
+         */
+        storage: vscode.Memento;
     }
 
 }
diff --git a/editors/code/src/installation/server.ts b/editors/code/src/installation/server.ts
index 406e2299c..80cb719e3 100644
--- a/editors/code/src/installation/server.ts
+++ b/editors/code/src/installation/server.ts
@@ -1,63 +1,15 @@
 import * as vscode from "vscode";
 import * as path from "path";
 import { strict as assert } from "assert";
-import { promises as fs } from "fs";
 import { promises as dns } from "dns";
 import { spawnSync } from "child_process";
-import { throttle } from "throttle-debounce";
 
 import { BinarySource } from "./interfaces";
-import { fetchLatestArtifactReleaseInfo } from "./fetch_latest_artifact_release_info";
-import { downloadFile } from "./download_file";
-
-export async function downloadLatestServer(
-    {file: artifactFileName, dir: installationDir, repo}: BinarySource.GithubRelease
-) {
-    const { releaseName, downloadUrl } = (await fetchLatestArtifactReleaseInfo(
-        repo, artifactFileName
-    ))!;
-
-    await fs.mkdir(installationDir).catch(err => assert.strictEqual(
-        err?.code,
-        "EEXIST",
-        `Couldn't create directory "${installationDir}" to download `+
-        `language server binary: ${err.message}`
-    ));
-
-    const installationPath = path.join(installationDir, artifactFileName);
-
-    console.time("Downloading ra_lsp_server");
-    await vscode.window.withProgress(
-        {
-            location: vscode.ProgressLocation.Notification,
-            cancellable: false, // FIXME: add support for canceling download?
-            title: `Downloading language server (${releaseName})`
-        },
-        async (progress, _cancellationToken) => {
-            let lastPrecentage = 0;
-            const filePermissions = 0o755; // (rwx, r_x, r_x)
-            await downloadFile(downloadUrl, installationPath, filePermissions, throttle(
-                200,
-                /* noTrailing: */ true,
-                (readBytes, totalBytes) => {
-                    const newPercentage = (readBytes / totalBytes) * 100;
-                    progress.report({
-                        message: newPercentage.toFixed(0) + "%",
-                        increment: newPercentage - lastPrecentage
-                    });
-
-                    lastPrecentage = newPercentage;
-                })
-            );
-        }
-    );
-    console.timeEnd("Downloading ra_lsp_server");
-}
-export async function ensureServerBinary(
-    serverSource: null | BinarySource
-): Promise<null | string> {
+import { fetchArtifactReleaseInfo } from "./fetch_artifact_release_info";
+import { downloadArtifact } from "./download_artifact";
 
-    if (!serverSource) {
+export async function ensureServerBinary(source: null | BinarySource): Promise<null | string> {
+    if (!source) {
         vscode.window.showErrorMessage(
             "Unfortunately we don't ship binaries for your platform yet. " +
             "You need to manually clone rust-analyzer repository and " +
@@ -69,80 +21,104 @@ export async function ensureServerBinary(
         return null;
     }
 
-    switch (serverSource.type) {
+    switch (source.type) {
         case BinarySource.Type.ExplicitPath: {
-            if (isBinaryAvailable(serverSource.path)) {
-                return serverSource.path;
+            if (isBinaryAvailable(source.path)) {
+                return source.path;
             }
 
             vscode.window.showErrorMessage(
-                `Unable to run ${serverSource.path} binary. ` +
+                `Unable to run ${source.path} binary. ` +
                 `To use the pre-built language server, set "rust-analyzer.raLspServerPath" ` +
                 "value to `null` or remove it from the settings to use it by default."
             );
             return null;
         }
         case BinarySource.Type.GithubRelease: {
-            const prebuiltBinaryPath = path.join(serverSource.dir, serverSource.file);
+            const prebuiltBinaryPath = path.join(source.dir, source.file);
+
+            const installedVersion: null | string = getServerVersion(source.storage);
+            const requiredVersion: string = source.version;
 
-            if (isBinaryAvailable(prebuiltBinaryPath)) {
+            console.log("Installed version:", installedVersion, "required:", requiredVersion);
+
+            if (isBinaryAvailable(prebuiltBinaryPath) && installedVersion == requiredVersion) {
+                // FIXME: check for new releases and notify the user to update if possible
                 return prebuiltBinaryPath;
             }
 
             const userResponse = await vscode.window.showInformationMessage(
-                "Language server binary for rust-analyzer was not found. " +
+                `Language server version ${source.version} for rust-analyzer is not installed. ` +
                 "Do you want to download it now?",
                 "Download now", "Cancel"
             );
             if (userResponse !== "Download now") return null;
 
-            try {
-                await downloadLatestServer(serverSource);
-            } catch (err) {
-                vscode.window.showErrorMessage(
-                    `Failed to download language server from ${serverSource.repo.name} ` +
-                    `GitHub repository: ${err.message}`
-                );
+            if (!await downloadServer(source)) return null;
 
-                console.error(err);
+            return prebuiltBinaryPath;
+        }
+    }
+}
 
-                dns.resolve('example.com').then(
-                    addrs => console.log("DNS resolution for example.com was successful", addrs),
-                    err => {
-                        console.error(
-                            "DNS resolution for example.com failed, " +
-                            "there might be an issue with Internet availability"
-                        );
-                        console.error(err);
-                    }
-                );
+async function downloadServer(source: BinarySource.GithubRelease): Promise<boolean> {
+    try {
+        const releaseInfo = (await fetchArtifactReleaseInfo(source.repo, source.file, source.version))!;
+
+        await downloadArtifact(releaseInfo, source.file, source.dir, "language server");
+        await setServerVersion(source.storage, releaseInfo.releaseName);
+    } catch (err) {
+        vscode.window.showErrorMessage(
+            `Failed to download language server from ${source.repo.name} ` +
+            `GitHub repository: ${err.message}`
+        );
+
+        console.error(err);
 
-                return null;
+        dns.resolve('example.com').then(
+            addrs => console.log("DNS resolution for example.com was successful", addrs),
+            err => {
+                console.error(
+                    "DNS resolution for example.com failed, " +
+                    "there might be an issue with Internet availability"
+                );
+                console.error(err);
             }
+        );
+        return false;
+    }
 
-            if (!isBinaryAvailable(prebuiltBinaryPath)) assert(false,
-                `Downloaded language server binary is not functional.` +
-                `Downloaded from: ${JSON.stringify(serverSource)}`
-            );
+    if (!isBinaryAvailable(path.join(source.dir, source.file))) assert(false,
+        `Downloaded language server binary is not functional.` +
+        `Downloaded from: ${JSON.stringify(source, null, 4)}`
+    );
 
+    vscode.window.showInformationMessage(
+        "Rust analyzer language server was successfully installed 🦀"
+    );
 
-            vscode.window.showInformationMessage(
-                "Rust analyzer language server was successfully installed 🦀"
-            );
+    return true;
+}
 
-            return prebuiltBinaryPath;
-        }
-    }
+function isBinaryAvailable(binaryPath: string): boolean {
+    const res = spawnSync(binaryPath, ["--version"]);
 
-    function isBinaryAvailable(binaryPath: string) {
-        const res = spawnSync(binaryPath, ["--version"]);
+    // ACHTUNG! `res` type declaration is inherently wrong, see
+    // https://github.com/DefinitelyTyped/DefinitelyTyped/issues/42221
 
-        // ACHTUNG! `res` type declaration is inherently wrong, see
-        // https://github.com/DefinitelyTyped/DefinitelyTyped/issues/42221
+    console.log("Checked binary availablity via --version", res);
+    console.log(binaryPath, "--version output:", res.output?.map(String));
 
-        console.log("Checked binary availablity via --version", res);
-        console.log(binaryPath, "--version output:", res.output?.map(String));
+    return res.status === 0;
+}
 
-        return res.status === 0;
-    }
+function getServerVersion(storage: vscode.Memento): null | string {
+    const version = storage.get<null | string>("server-version", null);
+    console.log("Get server-version:", version);
+    return version;
+}
+
+async function setServerVersion(storage: vscode.Memento, version: string): Promise<void> {
+    console.log("Set server-version:", version);
+    await storage.update("server-version", version.toString());
 }