12 files changed, 435 insertions, 147 deletions

diff --git a/editors/code/package-lock.json b/editors/code/package-lock.json
index b07964546..575dc7c4a 100644
--- a/editors/code/package-lock.json
+++ b/editors/code/package-lock.json
@@ -1,6 +1,6 @@
 {
     "name": "rust-analyzer",
-    "version": "0.2.20200211-dev",
+    "version": "0.2.20200309-nightly",
     "lockfileVersion": 1,
     "requires": true,
     "dependencies": {
diff --git a/editors/code/package.json b/editors/code/package.json
index 3aaae357a..faf10528d 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -6,7 +6,7 @@
     "private": true,
     "icon": "icon.png",
     "//": "The real version is in release.yaml, this one just needs to be bigger",
-    "version": "0.2.20200211-dev",
+    "version": "0.2.20200309-nightly",
     "publisher": "matklad",
     "repository": {
         "url": "https://github.com/rust-analyzer/rust-analyzer.git",
@@ -219,6 +219,19 @@
                         }
                     }
                 },
+                "rust-analyzer.updates.channel": {
+                    "type": "string",
+                    "enum": [
+                        "stable",
+                        "nightly"
+                    ],
+                    "default": "stable",
+                    "markdownEnumDescriptions": [
+                        "`\"stable\"` updates are shipped weekly, they don't contain cutting-edge features from VSCode proposed APIs but have less bugs in general",
+                        "`\"nightly\"` updates are shipped daily, they contain cutting-edge features and latest bug fixes. These releases help us get your feedback very quickly and speed up rust-analyzer development **drastically**"
+                    ],
+                    "markdownDescription": "Choose `\"nightly\"` updates to get the latest features and bug fixes every day. While `\"stable\"` releases occur weekly and don't contain cutting-edge features from VSCode proposed APIs"
+                },
                 "rust-analyzer.updates.askBeforeDownload": {
                     "type": "boolean",
                     "default": true,
@@ -235,7 +248,7 @@
                         "string"
                     ],
                     "default": null,
-                    "description": "Path to rust-analyzer executable (points to bundled binary by default)"
+                    "description": "Path to rust-analyzer executable (points to bundled binary by default). If this is set, then \"rust-analyzer.updates.channel\" setting is not used"
                 },
                 "rust-analyzer.excludeGlobs": {
                     "type": "array",
diff --git a/editors/code/src/commands/server_version.ts b/editors/code/src/commands/server_version.ts
index 421301b42..c4d84b443 100644
--- a/editors/code/src/commands/server_version.ts
+++ b/editors/code/src/commands/server_version.ts
@@ -5,7 +5,7 @@ import { spawnSync } from 'child_process';
 
 export function serverVersion(ctx: Ctx): Cmd {
     return async () => {
-        const binaryPath = await ensureServerBinary(ctx.config.serverSource);
+        const binaryPath = await ensureServerBinary(ctx.config);
 
         if (binaryPath == null) {
             throw new Error(
@@ -18,4 +18,3 @@ export function serverVersion(ctx: Ctx): Cmd {
         vscode.window.showInformationMessage('rust-analyzer version : ' + version);
     };
 }
-
diff --git a/editors/code/src/config.ts b/editors/code/src/config.ts
index 6db073bec..f63e1d20e 100644
--- a/editors/code/src/config.ts
+++ b/editors/code/src/config.ts
@@ -1,7 +1,7 @@
 import * as os from "os";
 import * as vscode from 'vscode';
 import { ArtifactSource } from "./installation/interfaces";
-import { log } from "./util";
+import { log, vscodeReloadWindow } from "./util";
 
 const RA_LSP_DEBUG = process.env.__RA_LSP_SERVER_DEBUG;
 
@@ -23,25 +23,40 @@ export interface CargoFeatures {
     allFeatures: boolean;
     features: string[];
 }
+
+export const enum UpdatesChannel {
+    Stable = "stable",
+    Nightly = "nightly"
+}
+
+export const NIGHTLY_TAG = "nightly";
 export class Config {
-    private static readonly rootSection = "rust-analyzer";
-    private static readonly requiresReloadOpts = [
+    readonly extensionId = "matklad.rust-analyzer";
+
+    private readonly rootSection = "rust-analyzer";
+    private readonly requiresReloadOpts = [
+        "serverPath",
         "cargoFeatures",
         "cargo-watch",
         "highlighting.semanticTokens",
         "inlayHints",
     ]
-        .map(opt => `${Config.rootSection}.${opt}`);
+        .map(opt => `${this.rootSection}.${opt}`);
 
-    private static readonly extensionVersion: string = (() => {
-        const packageJsonVersion = vscode
-            .extensions
-            .getExtension("matklad.rust-analyzer")!
-            .packageJSON
-            .version as string; // n.n.YYYYMMDD
+    readonly packageJsonVersion = vscode
+        .extensions
+        .getExtension(this.extensionId)!
+        .packageJSON
+        .version as string; // n.n.YYYYMMDD[-nightly]
+
+    /**
+     * Either `nightly` or `YYYY-MM-DD` (i.e. `stable` release)
+     */
+    readonly extensionReleaseTag: string = (() => {
+        if (this.packageJsonVersion.endsWith(NIGHTLY_TAG)) return NIGHTLY_TAG;
 
         const realVersionRegexp = /^\d+\.\d+\.(\d{4})(\d{2})(\d{2})/;
-        const [, yyyy, mm, dd] = packageJsonVersion.match(realVersionRegexp)!;
+        const [, yyyy, mm, dd] = this.packageJsonVersion.match(realVersionRegexp)!;
 
         return `${yyyy}-${mm}-${dd}`;
     })();
@@ -54,16 +69,19 @@ export class Config {
     }
 
     private refreshConfig() {
-        this.cfg = vscode.workspace.getConfiguration(Config.rootSection);
+        this.cfg = vscode.workspace.getConfiguration(this.rootSection);
         const enableLogging = this.cfg.get("trace.extension") as boolean;
         log.setEnabled(enableLogging);
-        log.debug("Using configuration:", this.cfg);
+        log.debug(
+            "Extension version:", this.packageJsonVersion,
+            "using configuration:", this.cfg
+        );
     }
 
     private async onConfigChange(event: vscode.ConfigurationChangeEvent) {
         this.refreshConfig();
 
-        const requiresReloadOpt = Config.requiresReloadOpts.find(
+        const requiresReloadOpt = this.requiresReloadOpts.find(
             opt => event.affectsConfiguration(opt)
         );
 
@@ -75,7 +93,7 @@ export class Config {
         );
 
         if (userResponse === "Reload now") {
-            vscode.commands.executeCommand("workbench.action.reloadWindow");
+            await vscodeReloadWindow();
         }
     }
 
@@ -121,8 +139,14 @@ export class Config {
         }
     }
 
+    get installedExtensionUpdateChannel(): UpdatesChannel {
+        return this.extensionReleaseTag === NIGHTLY_TAG
+            ? UpdatesChannel.Nightly
+            : UpdatesChannel.Stable;
+    }
+
     get serverSource(): null | ArtifactSource {
-        const serverPath = RA_LSP_DEBUG ?? this.cfg.get<null | string>("serverPath");
+        const serverPath = RA_LSP_DEBUG ?? this.serverPath;
 
         if (serverPath) {
             return {
@@ -135,13 +159,18 @@ export class Config {
 
         if (!prebuiltBinaryName) return null;
 
+        return this.createGithubReleaseSource(
+            prebuiltBinaryName,
+            this.extensionReleaseTag
+        );
+    }
+
+    private createGithubReleaseSource(file: string, tag: string): ArtifactSource.GithubRelease {
         return {
             type: ArtifactSource.Type.GithubRelease,
+            file,
+            tag,
             dir: this.ctx.globalStoragePath,
-            file: prebuiltBinaryName,
-            storage: this.ctx.globalState,
-            tag: Config.extensionVersion,
-            askBeforeDownload: this.cfg.get("updates.askBeforeDownload") as boolean,
             repo: {
                 name: "rust-analyzer",
                 owner: "rust-analyzer",
@@ -149,9 +178,23 @@ export class Config {
         };
     }
 
+    get nightlyVsixSource(): ArtifactSource.GithubRelease {
+        return this.createGithubReleaseSource("rust-analyzer.vsix", NIGHTLY_TAG);
+    }
+
+    readonly installedNightlyExtensionReleaseDate = new DateStorage(
+        "installed-nightly-extension-release-date",
+        this.ctx.globalState
+    );
+    readonly serverReleaseDate = new DateStorage("server-release-date", this.ctx.globalState);
+    readonly serverReleaseTag = new Storage<null | string>("server-release-tag", this.ctx.globalState, null);
+
     // We don't do runtime config validation here for simplicity. More on stackoverflow:
     // https://stackoverflow.com/questions/60135780/what-is-the-best-way-to-type-check-the-configuration-for-vscode-extension
 
+    private get serverPath() { return this.cfg.get("serverPath") as null | string; }
+    get updatesChannel() { return this.cfg.get("updates.channel") as UpdatesChannel; }
+    get askBeforeDownload() { return this.cfg.get("updates.askBeforeDownload") as boolean; }
     get highlightingSemanticTokens() { return this.cfg.get("highlighting.semanticTokens") as boolean; }
     get highlightingOn() { return this.cfg.get("highlightingOn") as boolean; }
     get rainbowHighlightingOn() { return this.cfg.get("rainbowHighlightingOn") as boolean; }
@@ -189,3 +232,37 @@ export class Config {
     // for internal use
     get withSysroot() { return this.cfg.get("withSysroot", true) as boolean; }
 }
+
+export class Storage<T> {
+    constructor(
+        private readonly key: string,
+        private readonly storage: vscode.Memento,
+        private readonly defaultVal: T
+    ) { }
+
+    get(): T {
+        const val = this.storage.get(this.key, this.defaultVal);
+        log.debug(this.key, "==", val);
+        return val;
+    }
+    async set(val: T) {
+        log.debug(this.key, "=", val);
+        await this.storage.update(this.key, val);
+    }
+}
+export class DateStorage {
+    inner: Storage<null | string>;
+
+    constructor(key: string, storage: vscode.Memento) {
+        this.inner = new Storage(key, storage, null);
+    }
+
+    get(): null | Date {
+        const dateStr = this.inner.get();
+        return dateStr ? new Date(dateStr) : null;
+    }
+
+    async set(date: null | Date) {
+        await this.inner.set(date ? date.toString() : null);
+    }
+}
diff --git a/editors/code/src/installation/download_artifact.ts b/editors/code/src/installation/download_artifact.ts
deleted file mode 100644
index 97e4d67c2..000000000
--- a/editors/code/src/installation/download_artifact.ts
+++ /dev/null
@@ -1,50 +0,0 @@
-import * as vscode from "vscode";
-import * as path from "path";
-import { promises as fs } from "fs";
-
-import { ArtifactReleaseInfo } from "./interfaces";
-import { downloadFile } from "./download_file";
-import { assert } from "../util";
-
-/**
- * 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(
-        err?.code === "EEXIST",
-        `Couldn't create directory "${installationDir}" to download ` +
-        `${artifactFileName} artifact: ${err?.message}`
-    ));
-
-    const installationPath = path.join(installationDir, 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, (readBytes, totalBytes) => {
-                const newPercentage = (readBytes / totalBytes) * 100;
-                progress.report({
-                    message: newPercentage.toFixed(0) + "%",
-                    increment: newPercentage - lastPrecentage
-                });
-
-                lastPrecentage = newPercentage;
-            });
-        }
-    );
-}
diff --git a/editors/code/src/installation/download_file.ts b/editors/code/src/installation/downloads.ts
index ee8949d61..7ce2e2960 100644
--- a/editors/code/src/installation/download_file.ts
+++ b/editors/code/src/installation/downloads.ts
@@ -1,8 +1,11 @@
 import fetch from "node-fetch";
+import * as vscode from "vscode";
+import * as path from "path";
 import * as fs from "fs";
 import * as stream from "stream";
 import * as util from "util";
 import { log, assert } from "../util";
+import { ArtifactReleaseInfo } from "./interfaces";
 
 const pipeline = util.promisify(stream.pipeline);
 
@@ -49,3 +52,46 @@ export async function downloadFile(
         // Issue at nodejs repo: https://github.com/nodejs/node/issues/31776
     });
 }
+
+/**
+ * Downloads artifact from given `downloadUrl`.
+ * Creates `installationDir` if it is not yet created and puts 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 downloadArtifactWithProgressUi(
+    { downloadUrl, releaseName }: ArtifactReleaseInfo,
+    artifactFileName: string,
+    installationDir: string,
+    displayName: string,
+) {
+    await fs.promises.mkdir(installationDir).catch(err => assert(
+        err?.code === "EEXIST",
+        `Couldn't create directory "${installationDir}" to download ` +
+        `${artifactFileName} artifact: ${err?.message}`
+    ));
+
+    const installationPath = path.join(installationDir, artifactFileName);
+
+    await vscode.window.withProgress(
+        {
+            location: vscode.ProgressLocation.Notification,
+            cancellable: false, // FIXME: add support for canceling download?
+            title: `Downloading rust-analyzer ${displayName} (${releaseName})`
+        },
+        async (progress, _cancellationToken) => {
+            let lastPrecentage = 0;
+            const filePermissions = 0o755; // (rwx, r_x, r_x)
+            await downloadFile(downloadUrl, installationPath, filePermissions, (readBytes, totalBytes) => {
+                const newPercentage = (readBytes / totalBytes) * 100;
+                progress.report({
+                    message: newPercentage.toFixed(0) + "%",
+                    increment: newPercentage - lastPrecentage
+                });
+
+                lastPrecentage = newPercentage;
+            });
+        }
+    );
+}
diff --git a/editors/code/src/installation/extension.ts b/editors/code/src/installation/extension.ts
new file mode 100644
index 000000000..eea6fded2
--- /dev/null
+++ b/editors/code/src/installation/extension.ts
@@ -0,0 +1,144 @@
+import * as vscode from "vscode";
+import * as path from "path";
+import { promises as fs } from 'fs';
+
+import { vscodeReinstallExtension, vscodeReloadWindow, log, vscodeInstallExtensionFromVsix, assert, notReentrant } from "../util";
+import { Config, UpdatesChannel } from "../config";
+import { ArtifactReleaseInfo, ArtifactSource } from "./interfaces";
+import { downloadArtifactWithProgressUi } from "./downloads";
+import { fetchArtifactReleaseInfo } from "./fetch_artifact_release_info";
+
+const HEURISTIC_NIGHTLY_RELEASE_PERIOD_IN_HOURS = 25;
+
+/**
+ * Installs `stable` or latest `nightly` version or does nothing if the current
+ * extension version is what's needed according to `desiredUpdateChannel`.
+ */
+export async function ensureProperExtensionVersion(config: Config): Promise<never | void> {
+    // User has built lsp server from sources, she should manage updates manually
+    if (config.serverSource?.type === ArtifactSource.Type.ExplicitPath) return;
+
+    const currentUpdChannel = config.installedExtensionUpdateChannel;
+    const desiredUpdChannel = config.updatesChannel;
+
+    if (currentUpdChannel === UpdatesChannel.Stable) {
+        // Release date is present only when we are on nightly
+        await config.installedNightlyExtensionReleaseDate.set(null);
+    }
+
+    if (desiredUpdChannel === UpdatesChannel.Stable) {
+        // VSCode should handle updates for stable channel
+        if (currentUpdChannel === UpdatesChannel.Stable) return;
+
+        if (!await askToDownloadProperExtensionVersion(config)) return;
+
+        await vscodeReinstallExtension(config.extensionId);
+        await vscodeReloadWindow(); // never returns
+    }
+
+    if (currentUpdChannel === UpdatesChannel.Stable) {
+        if (!await askToDownloadProperExtensionVersion(config)) return;
+
+        return await tryDownloadNightlyExtension(config);
+    }
+
+    const currentExtReleaseDate = config.installedNightlyExtensionReleaseDate.get();
+
+    if (currentExtReleaseDate === null) {
+        void vscode.window.showErrorMessage(
+            "Nightly release date must've been set during the installation. " +
+            "Did you download and install the nightly .vsix package manually?"
+        );
+        throw new Error("Nightly release date was not set in globalStorage");
+    }
+
+    const dateNow = new Date;
+    const hoursSinceLastUpdate = diffInHours(currentExtReleaseDate, dateNow);
+    log.debug(
+        "Current rust-analyzer nightly was downloaded", hoursSinceLastUpdate,
+        "hours ago, namely:", currentExtReleaseDate, "and now is", dateNow
+    );
+
+    if (hoursSinceLastUpdate < HEURISTIC_NIGHTLY_RELEASE_PERIOD_IN_HOURS) {
+        return;
+    }
+    if (!await askToDownloadProperExtensionVersion(config, "The installed nightly version is most likely outdated. ")) {
+        return;
+    }
+
+    await tryDownloadNightlyExtension(config, releaseInfo => {
+        assert(
+            currentExtReleaseDate.getTime() === config.installedNightlyExtensionReleaseDate.get()?.getTime(),
+            "Other active VSCode instance has reinstalled the extension"
+        );
+
+        if (releaseInfo.releaseDate.getTime() === currentExtReleaseDate.getTime()) {
+            vscode.window.showInformationMessage(
+                "Whoops, it appears that your nightly version is up-to-date. " +
+                "There might be some problems with the upcomming nightly release " +
+                "or you traveled too far into the future. Sorry for that 😅! "
+            );
+            return false;
+        }
+        return true;
+    });
+}
+
+async function askToDownloadProperExtensionVersion(config: Config, reason = "") {
+    if (!config.askBeforeDownload) return true;
+
+    const stableOrNightly = config.updatesChannel === UpdatesChannel.Stable ? "stable" : "latest nightly";
+
+    // In case of reentering this function and showing the same info message
+    // (e.g. after we had shown this message, the user changed the config)
+    // vscode will dismiss the already shown one (i.e. return undefined).
+    // This behaviour is what we want, but likely it is not documented
+
+    const userResponse = await vscode.window.showInformationMessage(
+        reason + `Do you want to download the ${stableOrNightly} rust-analyzer extension ` +
+        `version and reload the window now?`,
+        "Download now", "Cancel"
+    );
+    return userResponse === "Download now";
+}
+
+/**
+ * Shutdowns the process in case of success (i.e. reloads the window) or throws an error.
+ *
+ * ACHTUNG!: this function has a crazy amount of state transitions, handling errors during
+ * each of them would result in a ton of code (especially accounting for cross-process
+ * shared mutable `globalState` access). Enforcing no reentrancy for this is best-effort.
+ */
+const tryDownloadNightlyExtension = notReentrant(async (
+    config: Config,
+    shouldDownload: (releaseInfo: ArtifactReleaseInfo) => boolean = () => true
+): Promise<never | void> => {
+    const vsixSource = config.nightlyVsixSource;
+    try {
+        const releaseInfo = await fetchArtifactReleaseInfo(vsixSource.repo, vsixSource.file, vsixSource.tag);
+
+        if (!shouldDownload(releaseInfo)) return;
+
+        await downloadArtifactWithProgressUi(releaseInfo, vsixSource.file, vsixSource.dir, "nightly extension");
+
+        const vsixPath = path.join(vsixSource.dir, vsixSource.file);
+
+        await vscodeInstallExtensionFromVsix(vsixPath);
+        await config.installedNightlyExtensionReleaseDate.set(releaseInfo.releaseDate);
+        await fs.unlink(vsixPath);
+
+        await vscodeReloadWindow(); // never returns
+    } catch (err) {
+        log.downloadError(err, "nightly extension", vsixSource.repo.name);
+    }
+});
+
+function diffInHours(a: Date, b: Date): number {
+    // Discard the time and time-zone information (to abstract from daylight saving time bugs)
+    // https://stackoverflow.com/a/15289883/9259330
+
+    const utcA = Date.UTC(a.getFullYear(), a.getMonth(), a.getDate());
+    const utcB = Date.UTC(b.getFullYear(), b.getMonth(), b.getDate());
+
+    return (utcA - utcB) / (1000 * 60 * 60);
+}
diff --git a/editors/code/src/installation/fetch_artifact_release_info.ts b/editors/code/src/installation/fetch_artifact_release_info.ts
index b1b5a3485..1ad3b8338 100644
--- a/editors/code/src/installation/fetch_artifact_release_info.ts
+++ b/editors/code/src/installation/fetch_artifact_release_info.ts
@@ -59,12 +59,15 @@ export async function fetchArtifactReleaseInfo(
 
     return {
         releaseName: release.name,
+        releaseDate: new Date(release.published_at),
         downloadUrl: artifact.browser_download_url
     };
 
     // We omit declaration of tremendous amount of fields that we are not using here
     interface GithubRelease {
         name: string;
+        // eslint-disable-next-line camelcase
+        published_at: string;
         assets: Array<{
             name: string;
             // eslint-disable-next-line camelcase
diff --git a/editors/code/src/installation/interfaces.ts b/editors/code/src/installation/interfaces.ts
index 50b635921..1a8ea0884 100644
--- a/editors/code/src/installation/interfaces.ts
+++ b/editors/code/src/installation/interfaces.ts
@@ -1,5 +1,3 @@
-import * as vscode from "vscode";
-
 export interface GithubRepo {
     name: string;
     owner: string;
@@ -9,6 +7,7 @@ export interface GithubRepo {
  * Metadata about particular artifact retrieved from GitHub releases.
  */
 export interface ArtifactReleaseInfo {
+    releaseDate: Date;
     releaseName: string;
     downloadUrl: string;
 }
@@ -42,6 +41,9 @@ export namespace ArtifactSource {
          */
         repo: GithubRepo;
 
+
+        // FIXME: add installationPath: string;
+
         /**
          * Directory on the filesystem where the bundled binary is stored.
          */
@@ -57,17 +59,5 @@ export namespace ArtifactSource {
          * Tag of github release that denotes a version required by this extension.
          */
         tag: string;
-
-        /**
-         * Object that provides `get()/update()` operations to store metadata
-         * about the actual binary, e.g. its actual version.
-         */
-        storage: vscode.Memento;
-
-        /**
-         * Ask for the user permission before downloading the artifact.
-         */
-        askBeforeDownload: boolean;
     }
-
 }
diff --git a/editors/code/src/installation/server.ts b/editors/code/src/installation/server.ts
index ef1c45ff6..05730a778 100644
--- a/editors/code/src/installation/server.ts
+++ b/editors/code/src/installation/server.ts
@@ -1,14 +1,16 @@
 import * as vscode from "vscode";
 import * as path from "path";
-import { promises as dns } from "dns";
 import { spawnSync } from "child_process";
 
 import { ArtifactSource } from "./interfaces";
 import { fetchArtifactReleaseInfo } from "./fetch_artifact_release_info";
-import { downloadArtifact } from "./download_artifact";
-import { log, assert } from "../util";
+import { downloadArtifactWithProgressUi } from "./downloads";
+import { log, assert, notReentrant } from "../util";
+import { Config, NIGHTLY_TAG } from "../config";
+
+export async function ensureServerBinary(config: Config): Promise<null | string> {
+    const source = config.serverSource;
 
-export async function ensureServerBinary(source: null | ArtifactSource): Promise<null | string> {
     if (!source) {
         vscode.window.showErrorMessage(
             "Unfortunately we don't ship binaries for your platform yet. " +
@@ -35,18 +37,11 @@ export async function ensureServerBinary(source: null | ArtifactSource): Promise
             return null;
         }
         case ArtifactSource.Type.GithubRelease: {
-            const prebuiltBinaryPath = path.join(source.dir, source.file);
-
-            const installedVersion: null | string = getServerVersion(source.storage);
-            const requiredVersion: string = source.tag;
-
-            log.debug("Installed version:", installedVersion, "required:", requiredVersion);
-
-            if (isBinaryAvailable(prebuiltBinaryPath) && installedVersion === requiredVersion) {
-                return prebuiltBinaryPath;
+            if (!shouldDownloadServer(source, config)) {
+                return path.join(source.dir, source.file);
             }
 
-            if (source.askBeforeDownload) {
+            if (config.askBeforeDownload) {
                 const userResponse = await vscode.window.showInformationMessage(
                     `Language server version ${source.tag} for rust-analyzer is not installed. ` +
                     "Do you want to download it now?",
@@ -55,38 +50,56 @@ export async function ensureServerBinary(source: null | ArtifactSource): Promise
                 if (userResponse !== "Download now") return null;
             }
 
-            if (!await downloadServer(source)) return null;
-
-            return prebuiltBinaryPath;
+            return await downloadServer(source, config);
         }
     }
 }
 
-async function downloadServer(source: ArtifactSource.GithubRelease): Promise<boolean> {
+function shouldDownloadServer(
+    source: ArtifactSource.GithubRelease,
+    config: Config
+): boolean {
+    if (!isBinaryAvailable(path.join(source.dir, source.file))) return true;
+
+    const installed = {
+        tag: config.serverReleaseTag.get(),
+        date: config.serverReleaseDate.get()
+    };
+    const required = {
+        tag: source.tag,
+        date: config.installedNightlyExtensionReleaseDate.get()
+    };
+
+    log.debug("Installed server:", installed, "required:", required);
+
+    if (required.tag !== NIGHTLY_TAG || installed.tag !== NIGHTLY_TAG) {
+        return required.tag !== installed.tag;
+    }
+
+    assert(required.date !== null, "Extension release date should have been saved during its installation");
+    assert(installed.date !== null, "Server release date should have been saved during its installation");
+
+    return installed.date.getTime() !== required.date.getTime();
+}
+
+/**
+ * Enforcing no reentrancy for this is best-effort.
+ */
+const downloadServer = notReentrant(async (
+    source: ArtifactSource.GithubRelease,
+    config: Config,
+): Promise<null | string> => {
     try {
         const releaseInfo = await fetchArtifactReleaseInfo(source.repo, source.file, source.tag);
 
-        await downloadArtifact(releaseInfo, source.file, source.dir, "language server");
-        await setServerVersion(source.storage, releaseInfo.releaseName);
+        await downloadArtifactWithProgressUi(releaseInfo, source.file, source.dir, "language server");
+        await Promise.all([
+            config.serverReleaseTag.set(releaseInfo.releaseName),
+            config.serverReleaseDate.set(releaseInfo.releaseDate)
+        ]);
     } catch (err) {
-        vscode.window.showErrorMessage(
-            `Failed to download language server from ${source.repo.name} ` +
-            `GitHub repository: ${err.message}`
-        );
-
-        log.error(err);
-
-        dns.resolve('example.com').then(
-            addrs => log.debug("DNS resolution for example.com was successful", addrs),
-            err => {
-                log.error(
-                    "DNS resolution for example.com failed, " +
-                    "there might be an issue with Internet availability"
-                );
-                log.error(err);
-            }
-        );
-        return false;
+        log.downloadError(err, "language server", source.repo.name);
+        return null;
     }
 
     const binaryPath = path.join(source.dir, source.file);
@@ -101,8 +114,8 @@ async function downloadServer(source: ArtifactSource.GithubRelease): Promise<boo
         "Rust analyzer language server was successfully installed 🦀"
     );
 
-    return true;
-}
+    return binaryPath;
+});
 
 function isBinaryAvailable(binaryPath: string): boolean {
     const res = spawnSync(binaryPath, ["--version"]);
@@ -115,14 +128,3 @@ function isBinaryAvailable(binaryPath: string): boolean {
 
     return res.status === 0;
 }
-
-function getServerVersion(storage: vscode.Memento): null | string {
-    const version = storage.get<null | string>("server-version", null);
-    log.debug("Get server-version:", version);
-    return version;
-}
-
-async function setServerVersion(storage: vscode.Memento, version: string): Promise<void> {
-    log.debug("Set server-version:", version);
-    await storage.update("server-version", version.toString());
-}
diff --git a/editors/code/src/main.ts b/editors/code/src/main.ts
index e01c89cc7..bd4661a36 100644
--- a/editors/code/src/main.ts
+++ b/editors/code/src/main.ts
@@ -8,6 +8,7 @@ import { activateHighlighting } from './highlighting';
 import { ensureServerBinary } from './installation/server';
 import { Config } from './config';
 import { log } from './util';
+import { ensureProperExtensionVersion } from './installation/extension';
 
 let ctx: Ctx | undefined;
 
@@ -34,7 +35,13 @@ export async function activate(context: vscode.ExtensionContext) {
 
     const config = new Config(context);
 
-    const serverPath = await ensureServerBinary(config.serverSource);
+    vscode.workspace.onDidChangeConfiguration(() => ensureProperExtensionVersion(config).catch(log.error));
+
+    // Don't await the user response here, otherwise we will block the lsp server bootstrap
+    void ensureProperExtensionVersion(config).catch(log.error);
+
+    const serverPath = await ensureServerBinary(config);
+
     if (serverPath == null) {
         throw new Error(
             "Rust Analyzer Language Server is not available. " +
diff --git a/editors/code/src/util.ts b/editors/code/src/util.ts
index 95a5f1227..2bfc145e6 100644
--- a/editors/code/src/util.ts
+++ b/editors/code/src/util.ts
@@ -1,5 +1,6 @@
 import * as lc from "vscode-languageclient";
 import * as vscode from "vscode";
+import { promises as dns } from "dns";
 import { strict as nativeAssert } from "assert";
 
 export function assert(condition: boolean, explanation: string): asserts condition {
@@ -11,21 +12,40 @@ export function assert(condition: boolean, explanation: string): asserts conditi
     }
 }
 
-export const log = {
-    enabled: true,
+export const log = new class {
+    private enabled = true;
+
+    setEnabled(yes: boolean): void {
+        log.enabled = yes;
+    }
+
     debug(message?: any, ...optionalParams: any[]): void {
         if (!log.enabled) return;
         // eslint-disable-next-line no-console
         console.log(message, ...optionalParams);
-    },
+    }
+
     error(message?: any, ...optionalParams: any[]): void {
         if (!log.enabled) return;
         debugger;
         // eslint-disable-next-line no-console
         console.error(message, ...optionalParams);
-    },
-    setEnabled(yes: boolean): void {
-        log.enabled = yes;
+    }
+
+    downloadError(err: Error, artifactName: string, repoName: string) {
+        vscode.window.showErrorMessage(
+            `Failed to download the rust-analyzer ${artifactName} from ${repoName} ` +
+            `GitHub repository: ${err.message}`
+        );
+        log.error(err);
+        dns.resolve('example.com').then(
+            addrs => log.debug("DNS resolution for example.com was successful", addrs),
+            err => log.error(
+                "DNS resolution for example.com failed, " +
+                "there might be an issue with Internet availability",
+                err
+            )
+        );
     }
 };
 
@@ -66,6 +86,17 @@ function sleep(ms: number) {
     return new Promise(resolve => setTimeout(resolve, ms));
 }
 
+export function notReentrant<TThis, TParams extends any[], TRet>(
+    fn: (this: TThis, ...params: TParams) => Promise<TRet>
+): typeof fn {
+    let entered = false;
+    return function(...params) {
+        assert(!entered, `Reentrancy invariant for ${fn.name} is violated`);
+        entered = true;
+        return fn.apply(this, params).finally(() => entered = false);
+    };
+}
+
 export type RustDocument = vscode.TextDocument & { languageId: "rust" };
 export type RustEditor = vscode.TextEditor & { document: RustDocument; id: string };
 
@@ -79,3 +110,29 @@ export function isRustDocument(document: vscode.TextDocument): document is RustD
 export function isRustEditor(editor: vscode.TextEditor): editor is RustEditor {
     return isRustDocument(editor.document);
 }
+
+/**
+ * @param extensionId The canonical extension identifier in the form of: `publisher.name`
+ */
+export async function vscodeReinstallExtension(extensionId: string) {
+    // Unfortunately there is no straightforward way as of now, these commands
+    // were found in vscode source code.
+
+    log.debug("Uninstalling extension", extensionId);
+    await vscode.commands.executeCommand("workbench.extensions.uninstallExtension", extensionId);
+    log.debug("Installing extension", extensionId);
+    await vscode.commands.executeCommand("workbench.extensions.installExtension", extensionId);
+}
+
+export async function vscodeReloadWindow(): Promise<never> {
+    await vscode.commands.executeCommand("workbench.action.reloadWindow");
+
+    assert(false, "unreachable");
+}
+
+export async function vscodeInstallExtensionFromVsix(vsixPath: string) {
+    await vscode.commands.executeCommand(
+        "workbench.extensions.installExtension",
+        vscode.Uri.file(vsixPath)
+    );
+}