6 files changed, 137 insertions, 55 deletions

diff --git a/docs/user/features.md b/docs/user/features.md
index 09a7f5a43..cffbb4c7f 100644
--- a/docs/user/features.md
+++ b/docs/user/features.md
@@ -76,6 +76,14 @@ Shows internal statistic about memory usage of rust-analyzer
 
 Manually triggers GC
 
+#### Start Cargo Watch
+
+Start `cargo watch` for live error highlighting. Will prompt to install if it's not already installed.
+
+#### Stop Cargo Watch
+
+Stop `cargo watch`
+
 ### Code Actions (Assists)
 
 These are triggered in a particular context via light bulb. We use custom code on
diff --git a/editors/code/package.json b/editors/code/package.json
index a0454191a..83ceb19f7 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -119,6 +119,16 @@
                 "command": "rust-analyzer.reload",
                 "title": "Restart server",
                 "category": "Rust Analyzer"
+            },
+            {
+                "command": "rust-analyzer.startCargoWatch",
+                "title": "Start Cargo Watch",
+                "category": "Rust Analyzer"
+            },
+            {
+                "command": "rust-analyzer.stopCargoWatch",
+                "title": "Stop Cargo Watch",
+                "category": "Rust Analyzer"
             }
         ],
         "keybindings": [
@@ -250,6 +260,18 @@
                     "${workspaceRoot}"
                 ],
                 "pattern": "$rustc"
+            },
+            {
+                "name": "rustc-watch",
+                "fileLocation": [
+                    "relative",
+                    "${workspaceRoot}"
+                ],
+                "background": {
+                    "beginsPattern": "^\\[Running\\b",
+                    "endsPattern": "^\\[Finished running\\b"
+                },
+                "pattern": "$rustc"
             }
         ]
     }
diff --git a/editors/code/src/commands/cargo_watch.ts b/editors/code/src/commands/cargo_watch.ts
index 32bd38a1c..1d939e28c 100644
--- a/editors/code/src/commands/cargo_watch.ts
+++ b/editors/code/src/commands/cargo_watch.ts
@@ -7,44 +7,55 @@ import { terminate } from '../utils/processes';
 import { LineBuffer } from './line_buffer';
 import { StatusDisplay } from './watch_status';
 
-export class CargoWatchProvider {
-    private diagnosticCollection?: vscode.DiagnosticCollection;
-    private cargoProcess?: child_process.ChildProcess;
-    private outBuffer: string = '';
-    private statusDisplay?: StatusDisplay;
-    private outputChannel?: vscode.OutputChannel;
-
-    public activate(subscriptions: vscode.Disposable[]) {
-        let cargoExists = false;
-        const cargoTomlFile = path.join(
-            vscode.workspace.rootPath!,
-            'Cargo.toml'
+export function registerCargoWatchProvider(
+    subscriptions: vscode.Disposable[]
+): CargoWatchProvider | undefined {
+    let cargoExists = false;
+    const cargoTomlFile = path.join(vscode.workspace.rootPath!, 'Cargo.toml');
+    // Check if the working directory is valid cargo root path
+    try {
+        if (fs.existsSync(cargoTomlFile)) {
+            cargoExists = true;
+        }
+    } catch (err) {
+        cargoExists = false;
+    }
+
+    if (!cargoExists) {
+        vscode.window.showErrorMessage(
+            `Couldn\'t find \'Cargo.toml\' in ${cargoTomlFile}`
         );
-        // Check if the working directory is valid cargo root path
-        try {
-            if (fs.existsSync(cargoTomlFile)) {
-                cargoExists = true;
-            }
-        } catch (err) {
-            cargoExists = false;
-        }
+        return;
+    }
 
-        if (!cargoExists) {
-            vscode.window.showErrorMessage(
-                `Couldn\'t find \'Cargo.toml\' in ${cargoTomlFile}`
-            );
-            return;
-        }
+    const provider = new CargoWatchProvider();
+    subscriptions.push(provider);
+    return provider;
+}
 
-        subscriptions.push(this);
+export class CargoWatchProvider implements vscode.Disposable {
+    private readonly diagnosticCollection: vscode.DiagnosticCollection;
+    private readonly statusDisplay: StatusDisplay;
+    private readonly outputChannel: vscode.OutputChannel;
+    private cargoProcess?: child_process.ChildProcess;
+
+    constructor() {
         this.diagnosticCollection = vscode.languages.createDiagnosticCollection(
             'rustc'
         );
-
-        this.statusDisplay = new StatusDisplay(subscriptions);
+        this.statusDisplay = new StatusDisplay();
         this.outputChannel = vscode.window.createOutputChannel(
             'Cargo Watch Trace'
         );
+    }
+
+    public start() {
+        if (this.cargoProcess) {
+            vscode.window.showInformationMessage(
+                'Cargo Watch is already running'
+            );
+            return;
+        }
 
         let args = 'check --message-format json';
         if (Server.config.cargoWatchOptions.checkArguments.length > 0) {
@@ -95,25 +106,28 @@ export class CargoWatchProvider {
         this.logInfo('cargo-watch started.');
     }
 
-    public dispose(): void {
-        if (this.diagnosticCollection) {
-            this.diagnosticCollection.clear();
-            this.diagnosticCollection.dispose();
-        }
-
+    public stop() {
         if (this.cargoProcess) {
             this.cargoProcess.kill();
             terminate(this.cargoProcess);
+            this.cargoProcess = undefined;
+        } else {
+            vscode.window.showInformationMessage('Cargo Watch is not running');
         }
+    }
 
-        if (this.outputChannel) {
-            this.outputChannel.dispose();
-        }
+    public dispose(): void {
+        this.stop();
+
+        this.diagnosticCollection.clear();
+        this.diagnosticCollection.dispose();
+        this.outputChannel.dispose();
+        this.statusDisplay.dispose();
     }
 
     private logInfo(line: string) {
         if (Server.config.cargoWatchOptions.trace === 'verbose') {
-            this.outputChannel!.append(line);
+            this.outputChannel.append(line);
         }
     }
 
@@ -122,18 +136,18 @@ export class CargoWatchProvider {
             Server.config.cargoWatchOptions.trace === 'error' ||
             Server.config.cargoWatchOptions.trace === 'verbose'
         ) {
-            this.outputChannel!.append(line);
+            this.outputChannel.append(line);
         }
     }
 
     private parseLine(line: string) {
         if (line.startsWith('[Running')) {
-            this.diagnosticCollection!.clear();
-            this.statusDisplay!.show();
+            this.diagnosticCollection.clear();
+            this.statusDisplay.show();
         }
 
         if (line.startsWith('[Finished running')) {
-            this.statusDisplay!.hide();
+            this.statusDisplay.hide();
         }
 
         function getLevel(s: string): vscode.DiagnosticSeverity {
@@ -193,7 +207,7 @@ export class CargoWatchProvider {
 
             // The format of the package_id is "{name} {version} ({source_id})",
             // https://github.com/rust-lang/cargo/blob/37ad03f86e895bb80b474c1c088322634f4725f5/src/cargo/core/package_id.rs#L53
-            this.statusDisplay!.packageName = msg.package_id.split(' ')[0];
+            this.statusDisplay.packageName = msg.package_id.split(' ')[0];
         } else if (data.reason === 'compiler-message') {
             const msg = data.message as RustDiagnostic;
 
diff --git a/editors/code/src/commands/runnables.ts b/editors/code/src/commands/runnables.ts
index c4df24c79..26372c1e8 100644
--- a/editors/code/src/commands/runnables.ts
+++ b/editors/code/src/commands/runnables.ts
@@ -5,7 +5,7 @@ import * as vscode from 'vscode';
 import * as lc from 'vscode-languageclient';
 
 import { Server } from '../server';
-import { CargoWatchProvider } from './cargo_watch';
+import { CargoWatchProvider, registerCargoWatchProvider } from './cargo_watch';
 
 interface RunnablesParams {
     textDocument: lc.TextDocumentIdentifier;
@@ -137,7 +137,7 @@ export async function handleSingle(runnable: Runnable) {
  */
 export async function interactivelyStartCargoWatch(
     context: vscode.ExtensionContext
-) {
+): Promise<CargoWatchProvider | undefined> {
     if (Server.config.cargoWatchOptions.enableOnStartup === 'disabled') {
         return;
     }
@@ -153,6 +153,12 @@ export async function interactivelyStartCargoWatch(
         }
     }
 
+    return startCargoWatch(context);
+}
+
+export async function startCargoWatch(
+    context: vscode.ExtensionContext
+): Promise<CargoWatchProvider | undefined> {
     const execPromise = util.promisify(child_process.exec);
 
     const { stderr } = await execPromise('cargo watch --version').catch(e => e);
@@ -197,6 +203,9 @@ export async function interactivelyStartCargoWatch(
         }
     }
 
-    const validater = new CargoWatchProvider();
-    validater.activate(context.subscriptions);
+    const provider = await registerCargoWatchProvider(context.subscriptions);
+    if (provider) {
+        provider.start();
+    }
+    return provider;
 }
diff --git a/editors/code/src/commands/watch_status.ts b/editors/code/src/commands/watch_status.ts
index 86ae821de..a3b0178f2 100644
--- a/editors/code/src/commands/watch_status.ts
+++ b/editors/code/src/commands/watch_status.ts
@@ -2,19 +2,18 @@ import * as vscode from 'vscode';
 
 const spinnerFrames = ['⠋', '⠙', '⠹', '⠸', '⠼', '⠴', '⠦', '⠧', '⠇', '⠏'];
 
-export class StatusDisplay {
+export class StatusDisplay implements vscode.Disposable {
     public packageName?: string;
 
     private i = 0;
     private statusBarItem: vscode.StatusBarItem;
     private timer?: NodeJS.Timeout;
 
-    constructor(subscriptions: vscode.Disposable[]) {
+    constructor() {
         this.statusBarItem = vscode.window.createStatusBarItem(
             vscode.StatusBarAlignment.Left,
             10
         );
-        subscriptions.push(this.statusBarItem);
         this.statusBarItem.hide();
     }
 
@@ -33,7 +32,7 @@ export class StatusDisplay {
                 }
             }, 300);
 
-        this.statusBarItem!.show();
+        this.statusBarItem.show();
     }
 
     public hide() {
@@ -42,7 +41,16 @@ export class StatusDisplay {
             this.timer = undefined;
         }
 
-        this.statusBarItem!.hide();
+        this.statusBarItem.hide();
+    }
+
+    public dispose() {
+        if (this.timer) {
+            clearInterval(this.timer);
+            this.timer = undefined;
+        }
+
+        this.statusBarItem.dispose();
     }
 
     private frame() {
diff --git a/editors/code/src/extension.ts b/editors/code/src/extension.ts
index 1073a36a0..48dd2a614 100644
--- a/editors/code/src/extension.ts
+++ b/editors/code/src/extension.ts
@@ -2,7 +2,11 @@ import * as vscode from 'vscode';
 import * as lc from 'vscode-languageclient';
 
 import * as commands from './commands';
-import { interactivelyStartCargoWatch } from './commands/runnables';
+import { CargoWatchProvider } from './commands/cargo_watch';
+import {
+    interactivelyStartCargoWatch,
+    startCargoWatch
+} from './commands/runnables';
 import { SyntaxTreeContentProvider } from './commands/syntaxTree';
 import * as events from './events';
 import * as notifications from './notifications';
@@ -126,7 +130,24 @@ export function activate(context: vscode.ExtensionContext) {
     vscode.commands.registerCommand('rust-analyzer.reload', reloadCommand);
 
     // Executing `cargo watch` provides us with inline diagnostics on save
-    interactivelyStartCargoWatch(context);
+    let provider: CargoWatchProvider | undefined;
+    interactivelyStartCargoWatch(context).then(p => {
+        provider = p;
+    });
+    registerCommand('rust-analyzer.startCargoWatch', () => {
+        if (provider) {
+            provider.start();
+        } else {
+            startCargoWatch(context).then(p => {
+                provider = p;
+            });
+        }
+    });
+    registerCommand('rust-analyzer.stopCargoWatch', () => {
+        if (provider) {
+            provider.stop();
+        }
+    });
 
     // Start the language server, finally!
     startServer();