6 files changed, 239 insertions, 162 deletions

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/download_file.ts b/editors/code/src/installation/download_file.ts
index b51602ef9..d154f4816 100644
--- a/editors/code/src/installation/download_file.ts
+++ b/editors/code/src/installation/download_file.ts
@@ -1,9 +1,13 @@
 import fetch from "node-fetch";
 import * as fs from "fs";
+import * as stream from "stream";
+import * as util from "util";
 import { strict as assert } from "assert";
 
+const pipeline = util.promisify(stream.pipeline);
+
 /**
- * Downloads file from `url` and stores it at `destFilePath`.
+ * Downloads file from `url` and stores it at `destFilePath` with `destFilePermissions`.
  * `onProgress` callback is called on recieveing each chunk of bytes
  * to track the progress of downloading, it gets the already read and total
  * amount of bytes to read as its parameters.
@@ -11,24 +15,37 @@ import { strict as assert } from "assert";
 export async function downloadFile(
     url: string,
     destFilePath: fs.PathLike,
+    destFilePermissions: number,
     onProgress: (readBytes: number, totalBytes: number) => void
 ): Promise<void> {
-    const response = await fetch(url);
+    const res = await fetch(url);
+
+    if (!res.ok) {
+        console.log("Error", res.status, "while downloading file from", url);
+        console.dir({ body: await res.text(), headers: res.headers }, { depth: 3 });
 
-    const totalBytes = Number(response.headers.get('content-length'));
+        throw new Error(`Got response ${res.status} when trying to download a file.`);
+    }
+
+    const totalBytes = Number(res.headers.get('content-length'));
     assert(!Number.isNaN(totalBytes), "Sanity check of content-length protocol");
 
+    console.log("Downloading file of", totalBytes, "bytes size from", url, "to", destFilePath);
+
     let readBytes = 0;
+    res.body.on("data", (chunk: Buffer) => {
+        readBytes += chunk.length;
+        onProgress(readBytes, totalBytes);
+    });
 
-    console.log("Downloading file of", totalBytes, "bytes size from", url, "to", destFilePath);
+    const destFileStream = fs.createWriteStream(destFilePath, { mode: destFilePermissions });
+
+    await pipeline(res.body, destFileStream);
+    return new Promise<void>(resolve => {
+        destFileStream.on("close", resolve);
+        destFileStream.destroy();
 
-    return new Promise<void>((resolve, reject) => response.body
-        .on("data", (chunk: Buffer) => {
-            readBytes += chunk.length;
-            onProgress(readBytes, totalBytes);
-        })
-        .on("end", resolve)
-        .on("error", reject)
-        .pipe(fs.createWriteStream(destFilePath))
-    );
+        // Details on workaround: https://github.com/rust-analyzer/rust-analyzer/pull/3092#discussion_r378191131
+        // Issue at nodejs repo: https://github.com/nodejs/node/issues/31776
+    });
 }
diff --git a/editors/code/src/installation/fetch_latest_artifact_metadata.ts b/editors/code/src/installation/fetch_artifact_release_info.ts
index 7e3700603..7d497057a 100644
--- a/editors/code/src/installation/fetch_latest_artifact_metadata.ts
+++ b/editors/code/src/installation/fetch_artifact_release_info.ts
@@ -1,26 +1,32 @@
 import fetch from "node-fetch";
-import { GithubRepo, ArtifactMetadata } from "./interfaces";
+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 fetchLatestArtifactMetadata(
-    repo: GithubRepo, artifactFileName: string
-): Promise<null | ArtifactMetadata> {
+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 8039d0b90..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;
@@ -6,7 +8,7 @@ export interface GithubRepo {
 /**
  * Metadata about particular artifact retrieved from GitHub releases.
  */
-export interface ArtifactMetadata {
+export interface ArtifactReleaseInfo {
     releaseName: string;
     downloadUrl: 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/language_server.ts b/editors/code/src/installation/language_server.ts
deleted file mode 100644
index 1ce67b8b2..000000000
--- a/editors/code/src/installation/language_server.ts
+++ /dev/null
@@ -1,141 +0,0 @@
-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 { fetchLatestArtifactMetadata } from "./fetch_latest_artifact_metadata";
-import { downloadFile } from "./download_file";
-
-export async function downloadLatestLanguageServer(
-    {file: artifactFileName, dir: installationDir, repo}: BinarySource.GithubRelease
-) {
-    const { releaseName, downloadUrl } = (await fetchLatestArtifactMetadata(
-        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;
-            await downloadFile(downloadUrl, installationPath, 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");
-
-    await fs.chmod(installationPath, 0o755); // Set (rwx, r_x, r_x) permissions
-}
-export async function ensureLanguageServerBinary(
-    langServerSource: null | BinarySource
-): Promise<null | string> {
-
-    if (!langServerSource) {
-        vscode.window.showErrorMessage(
-            "Unfortunately we don't ship binaries for your platform yet. " +
-            "You need to manually clone rust-analyzer repository and " +
-            "run `cargo xtask install --server` to build the language server from sources. " +
-            "If you feel that your platform should be supported, please create an issue " +
-            "about that [here](https://github.com/rust-analyzer/rust-analyzer/issues) and we " +
-            "will consider it."
-        );
-        return null;
-    }
-
-    switch (langServerSource.type) {
-        case BinarySource.Type.ExplicitPath: {
-            if (isBinaryAvailable(langServerSource.path)) {
-                return langServerSource.path;
-            }
-
-            vscode.window.showErrorMessage(
-                `Unable to run ${langServerSource.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(langServerSource.dir, langServerSource.file);
-
-            if (isBinaryAvailable(prebuiltBinaryPath)) {
-                return prebuiltBinaryPath;
-            }
-
-            const userResponse = await vscode.window.showInformationMessage(
-                "Language server binary for rust-analyzer was not found. " +
-                "Do you want to download it now?",
-                "Download now", "Cancel"
-            );
-            if (userResponse !== "Download now") return null;
-
-            try {
-                await downloadLatestLanguageServer(langServerSource);
-            } catch (err) {
-                await vscode.window.showErrorMessage(
-                    `Failed to download language server from ${langServerSource.repo.name} ` +
-                    `GitHub repository: ${err.message}`
-                );
-
-                await dns.resolve('www.google.com').catch(err => {
-                    console.error("DNS resolution failed, there might be an issue with Internet availability");
-                    console.error(err);
-                });
-
-                return null;
-            }
-
-            if (!isBinaryAvailable(prebuiltBinaryPath)) assert(false,
-                `Downloaded language server binary is not functional.` +
-                `Downloaded from: ${JSON.stringify(langServerSource)}`
-            );
-
-
-            vscode.window.showInformationMessage(
-                "Rust analyzer language server was successfully installed 🦀"
-            );
-
-            return prebuiltBinaryPath;
-        }
-    }
-
-    function isBinaryAvailable(binaryPath: string) {
-        const res = spawnSync(binaryPath, ["--version"]);
-
-        // 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));
-
-        return res.status === 0;
-    }
-}
diff --git a/editors/code/src/installation/server.ts b/editors/code/src/installation/server.ts
new file mode 100644
index 000000000..80cb719e3
--- /dev/null
+++ b/editors/code/src/installation/server.ts
@@ -0,0 +1,124 @@
+import * as vscode from "vscode";
+import * as path from "path";
+import { strict as assert } from "assert";
+import { promises as dns } from "dns";
+import { spawnSync } from "child_process";
+
+import { BinarySource } from "./interfaces";
+import { fetchArtifactReleaseInfo } from "./fetch_artifact_release_info";
+import { downloadArtifact } from "./download_artifact";
+
+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 " +
+            "run `cargo xtask install --server` to build the language server from sources. " +
+            "If you feel that your platform should be supported, please create an issue " +
+            "about that [here](https://github.com/rust-analyzer/rust-analyzer/issues) and we " +
+            "will consider it."
+        );
+        return null;
+    }
+
+    switch (source.type) {
+        case BinarySource.Type.ExplicitPath: {
+            if (isBinaryAvailable(source.path)) {
+                return source.path;
+            }
+
+            vscode.window.showErrorMessage(
+                `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(source.dir, source.file);
+
+            const installedVersion: null | string = getServerVersion(source.storage);
+            const requiredVersion: string = source.version;
+
+            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 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;
+
+            if (!await downloadServer(source)) return null;
+
+            return prebuiltBinaryPath;
+        }
+    }
+}
+
+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);
+
+        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(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 🦀"
+    );
+
+    return true;
+}
+
+function isBinaryAvailable(binaryPath: string): boolean {
+    const res = spawnSync(binaryPath, ["--version"]);
+
+    // 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));
+
+    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());
+}