7 files changed, 210 insertions, 39 deletions

diff --git a/editors/code/src/client.ts b/editors/code/src/client.ts
index 7e7e909dd..7639ed44b 100644
--- a/editors/code/src/client.ts
+++ b/editors/code/src/client.ts
@@ -1,24 +1,18 @@
-import { homedir } from 'os';
 import * as lc from 'vscode-languageclient';
-import { spawnSync } from 'child_process';
 
 import { window, workspace } from 'vscode';
 import { Config } from './config';
+import { ensureLanguageServerBinary } from './installation/language_server';
 
-export function createClient(config: Config): lc.LanguageClient {
+export async function createClient(config: Config): Promise<null | lc.LanguageClient> {
     // '.' Is the fallback if no folder is open
     // TODO?: Workspace folders support Uri's (eg: file://test.txt).
     // It might be a good idea to test if the uri points to a file.
     const workspaceFolderPath = workspace.workspaceFolders?.[0]?.uri.fsPath ?? '.';
 
-    const raLspServerPath = expandPathResolving(config.raLspServerPath);
-    if (spawnSync(raLspServerPath, ["--version"]).status !== 0) {
-        window.showErrorMessage(
-            `Unable to execute '${raLspServerPath} --version'\n\n` +
-            `Perhaps it is not in $PATH?\n\n` +
-            `PATH=${process.env.PATH}\n`
-        );
-    }
+    const raLspServerPath = await ensureLanguageServerBinary(config.raLspServerSource);
+    if (!raLspServerPath) return null;
+
     const run: lc.Executable = {
         command: raLspServerPath,
         options: { cwd: workspaceFolderPath },
@@ -87,9 +81,3 @@ export function createClient(config: Config): lc.LanguageClient {
     res.registerProposedFeatures();
     return res;
 }
-function expandPathResolving(path: string) {
-    if (path.startsWith('~/')) {
-        return path.replace('~', homedir());
-    }
-    return path;
-}
diff --git a/editors/code/src/config.ts b/editors/code/src/config.ts
index 524620433..aca5dab5a 100644
--- a/editors/code/src/config.ts
+++ b/editors/code/src/config.ts
@@ -1,4 +1,6 @@
+import * as os from "os";
 import * as vscode from 'vscode';
+import { BinarySource, BinarySourceType } from "./installation/interfaces";
 
 const RA_LSP_DEBUG = process.env.__RA_LSP_SERVER_DEBUG;
 
@@ -16,10 +18,24 @@ 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;
+
     highlightingOn = true;
     rainbowHighlightingOn = false;
     enableEnhancedTyping = true;
-    raLspServerPath = RA_LSP_DEBUG || 'ra_lsp_server';
     lruCapacity: null | number = null;
     displayInlayHints = true;
     maxInlayHintLength: null | number = null;
@@ -45,11 +61,20 @@ export class Config {
     private prevCargoWatchOptions: null | CargoWatchOptions = null;
 
     constructor(ctx: vscode.ExtensionContext) {
-        vscode.workspace.onDidChangeConfiguration(_ => this.refresh(), null, ctx.subscriptions);
-        this.refresh();
+        vscode.workspace.onDidChangeConfiguration(_ => this.refresh(ctx), null, ctx.subscriptions);
+        this.refresh(ctx);
+    }
+
+    private static expandPathResolving(path: string) {
+        if (path.startsWith('~/')) {
+            return path.replace('~', os.homedir());
+        }
+        return path;
     }
 
-    private refresh() {
+    // 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) {
         const config = vscode.workspace.getConfiguration('rust-analyzer');
 
         let requireReloadMessage = null;
@@ -82,9 +107,26 @@ export class Config {
             this.prevEnhancedTyping = this.enableEnhancedTyping;
         }
 
-        if (config.has('raLspServerPath')) {
-            this.raLspServerPath =
-                RA_LSP_DEBUG || (config.get('raLspServerPath') as string);
+        {
+            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;
+            }
         }
 
         if (config.has('cargo-watch.enable')) {
diff --git a/editors/code/src/ctx.ts b/editors/code/src/ctx.ts
index a4dcc3037..f0e2d72f7 100644
--- a/editors/code/src/ctx.ts
+++ b/editors/code/src/ctx.ts
@@ -29,7 +29,11 @@ export class Ctx {
             await old.stop();
         }
         this.client = null;
-        const client = createClient(this.config);
+        const client = await createClient(this.config);
+        if (!client) {
+            throw new Error("Rust Analyzer Language Server is not available");
+        }
+
         this.pushCleanup(client.start());
         await client.onReady();
 
diff --git a/editors/code/src/github/download_file.ts b/editors/code/src/installation/download_file.ts
index f40750be9..7b537e114 100644
--- a/editors/code/src/github/download_file.ts
+++ b/editors/code/src/installation/download_file.ts
@@ -7,7 +7,7 @@ export async function downloadFile(
     destFilePath: fs.PathLike,
     onProgress: (readBytes: number, totalBytes: number) => void
 ): Promise<void> {
-    onProgress = throttle(100, /* noTrailing: */ true, onProgress);
+    onProgress = throttle(1000, /* noTrailing: */ true, onProgress);
 
     const response = await fetch(url);
 
diff --git a/editors/code/src/github/fetch_latest_artifact_metadata.ts b/editors/code/src/installation/fetch_latest_artifact_metadata.ts
index 52641ca67..f07431aac 100644
--- a/editors/code/src/github/fetch_latest_artifact_metadata.ts
+++ b/editors/code/src/installation/fetch_latest_artifact_metadata.ts
@@ -1,25 +1,19 @@
 import fetch from "node-fetch";
+import { GithubRepo, ArtifactMetadata } from "./interfaces";
 
 const GITHUB_API_ENDPOINT_URL = "https://api.github.com";
 
 export interface FetchLatestArtifactMetadataOpts {
-    repoName: string;
-    repoOwner: string;
+    repo: GithubRepo;
     artifactFileName: string;
 }
 
-export interface ArtifactMetadata {
-    releaseName: string;
-    releaseDate: Date;
-    downloadUrl: string;
-}
-
 export async function fetchLatestArtifactMetadata(
     opts: FetchLatestArtifactMetadataOpts
-): Promise<ArtifactMetadata | null> {
+): Promise<null | ArtifactMetadata> {
 
-    const repoOwner = encodeURIComponent(opts.repoOwner);
-    const repoName  = encodeURIComponent(opts.repoName);
+    const repoOwner = encodeURIComponent(opts.repo.owner);
+    const repoName  = encodeURIComponent(opts.repo.name);
 
     const apiEndpointPath = `/repos/${repoOwner}/${repoName}/releases/latest`;
     const requestUrl = GITHUB_API_ENDPOINT_URL + apiEndpointPath;
@@ -35,14 +29,12 @@ export async function fetchLatestArtifactMetadata(
 
     return !artifact ? null : {
         releaseName: response.name,
-        releaseDate: new Date(response.published_at),
         downloadUrl: artifact.browser_download_url
     };
 
     // Noise denotes tremendous amount of data that we are not using here
     interface GithubRelease {
         name: string;
-        published_at: Date;
         assets: Array<{
             browser_download_url: string;
 
diff --git a/editors/code/src/installation/interfaces.ts b/editors/code/src/installation/interfaces.ts
new file mode 100644
index 000000000..f54e24e26
--- /dev/null
+++ b/editors/code/src/installation/interfaces.ts
@@ -0,0 +1,26 @@
+export interface GithubRepo {
+    name: string;
+    owner: string;
+}
+
+export interface ArtifactMetadata {
+    releaseName: string;
+    downloadUrl: string;
+}
+
+
+export enum BinarySourceType { ExplicitPath, GithubBinary }
+
+export type BinarySource = EplicitPathSource | GithubBinarySource;
+
+export interface EplicitPathSource {
+    type: BinarySourceType.ExplicitPath;
+    path: string;
+}
+
+export interface GithubBinarySource {
+    type: BinarySourceType.GithubBinary;
+    repo: GithubRepo;
+    dir: string;
+    file: string;
+}
diff --git a/editors/code/src/installation/language_server.ts b/editors/code/src/installation/language_server.ts
new file mode 100644
index 000000000..2b3ce6621
--- /dev/null
+++ b/editors/code/src/installation/language_server.ts
@@ -0,0 +1,119 @@
+import { unwrapNotNil } from "ts-not-nil";
+import { spawnSync } from "child_process";
+import * as vscode from "vscode";
+import * as path from "path";
+import { strict as assert } from "assert";
+import { promises as fs } from "fs";
+
+import { BinarySource, BinarySourceType, GithubBinarySource } from "./interfaces";
+import { fetchLatestArtifactMetadata } from "./fetch_latest_artifact_metadata";
+import { downloadFile } from "./download_file";
+
+export async function downloadLatestLanguageServer(
+    {file: artifactFileName, dir: installationDir, repo}: GithubBinarySource
+) {
+    const binaryMetadata = await fetchLatestArtifactMetadata({ artifactFileName, repo });
+
+    const {
+        releaseName,
+        downloadUrl
+    } = unwrapNotNil(binaryMetadata, `Latest GitHub release lacks "${artifactFileName}" file`);
+
+    await fs.mkdir(installationDir).catch(err => assert.strictEqual(
+        err && err.code,
+        "EEXIST",
+        `Couldn't create directory "${installationDir}" to download `+
+        `language server binary: ${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 language server ${releaseName}`
+        },
+        async (progress, _) => {
+            let lastPrecentage = 0;
+            await downloadFile(downloadUrl, installationPath, (readBytes, totalBytes) => {
+                const newPercentage = (readBytes / totalBytes) * 100;
+                progress.report({
+                    message: newPercentage.toFixed(0) + "%",
+                    increment: newPercentage - lastPrecentage
+                });
+
+                lastPrecentage = newPercentage;
+            });
+        }
+    );
+
+    await fs.chmod(installationPath, 111); // Set xxx 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 BinarySourceType.ExplicitPath: {
+            if (isBinaryAvailable(langServerSource.path)) {
+                return langServerSource.path;
+            }
+            vscode.window.showErrorMessage(
+                `Unable to execute ${'`'}${langServerSource.path} --version${'`'}. ` +
+                "To use the bundled language server, set `rust-analyzer.raLspServerPath` " +
+                "value to `null` or remove it from the settings to use it by default."
+            );
+            return null;
+        }
+        case BinarySourceType.GithubBinary: {
+            const bundledBinaryPath = path.join(langServerSource.dir, langServerSource.file);
+
+            if (!isBinaryAvailable(bundledBinaryPath)) {
+                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}`
+                    );
+                    return null;
+                }
+
+
+                assert(
+                    isBinaryAvailable(bundledBinaryPath),
+                    "Downloaded language server binary is not functional"
+                );
+
+                vscode.window.showInformationMessage(
+                    "Rust analyzer language server was successfully installed"
+                );
+            }
+            return bundledBinaryPath;
+        }
+    }
+
+    function isBinaryAvailable(binaryPath: string) {
+        return spawnSync(binaryPath, ["--version"]).status === 0;
+    }
+}