Goimpl implementation (#939)

* Add goimpl to tools list.

* Support github.com/josharian/impl. Fixes #259.

Does some basic input validation to ensure the required information is
passed.

The regex included makes the receiver name optional, the intention there
is that if the receiver name isn't included, that the type the cursor is
in should be used as the receiver for the interface.

However, I think that the first step of just having the ability to use
goimpl was a important first step.

* Missing semicolon lint fix.

* Add `go.impl.cursor` to package.json

package.json

@@ -129,6 +129,11 @@
         "title": "Go: Generate Unit Tests For Function",
         "description": "Generates unit tests for the selected function in the current file"
       },
+      {
+        "command": "go.impl.cursor",
+        "title": "Go: Generate interface stub",
+        "description": "Generates and inserts stub methods for implementing the provided interface at the cursor."
+      },
       {
         "command": "go.import.add",
         "title": "Go: Add Import",
@@ -790,4 +795,4 @@
       ]
     }
   }
-}
+}

src/goImpl.ts

@@ -0,0 +1,69 @@
+/*---------------------------------------------------------
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ * Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------*/
+
+'use strict';
+
+import vscode = require('vscode');
+import cp = require('child_process');
+import { getBinPath } from './util';
+import { promptForMissingTool } from './goInstallTools';
+
+interface GoImplInput {
+	receiver: string;
+	interface: string;
+}
+
+// Supports only passing interface, see TODO in implCursor to finish
+const inputRegex = /^(\w+\ \*?\w+\ )?([\w.]+)$/;
+
+export function implCursor() {
+	let cursor = vscode.window.activeTextEditor.selection;
+	return vscode.window.showInputBox({
+		placeHolder: 'f *File io.Closer',
+		prompt: 'What interface do you want to implement?'
+	}).then(implInput => {
+		if (typeof implInput === 'undefined') {
+			return;
+		}
+		const matches = implInput.match(inputRegex);
+		if (!matches) {
+			vscode.window.showInformationMessage(`Not parsable input: ${implInput}`);
+			return;
+		}
+
+		// TODO: automatically detect type name at cursor
+		// if matches[1] is undefined then detect receiver type
+		// take first character and use as receiver name
+
+		let input: GoImplInput = {
+			receiver: matches[1],
+			interface: matches[2]
+		};
+
+		runGoImpl(input, cursor.start);
+	});
+}
+
+function runGoImpl(input: GoImplInput, insertPos: vscode.Position) {
+	let goimpl = getBinPath('impl');
+	let editor = vscode.window.activeTextEditor;
+	let p = cp.execFile(goimpl, [input.receiver, input.interface], (err, stdout, stderr) => {
+		if (err && (<any>err).code === 'ENOENT') {
+			promptForMissingTool('impl');
+			return;
+		}
+
+		if (err) {
+			vscode.window.showInformationMessage(`Cannot stub inteface: ${stderr}`);
+			return;
+		}
+
+		let output = stdout;
+		vscode.window.activeTextEditor.edit(editBuilder => {
+			editBuilder.insert(insertPos, stdout);
+		});
+	});
+	p.stdin.end();
+}

src/goInstallTools.ts

@@ -27,7 +27,8 @@ function getTools(goVersion: SemVersion): { [key: string]: string } {
 		'go-symbols': 'github.com/acroca/go-symbols',
 		'guru': 'golang.org/x/tools/cmd/guru',
 		'gorename': 'golang.org/x/tools/cmd/gorename',
-		'gomodifytags': 'github.com/fatih/gomodifytags'
+		'gomodifytags': 'github.com/fatih/gomodifytags',
+		'impl': 'github.com/josharian/impl'
 	};
 	if (goLiveErrorsEnabled()) {
 		tools['gotype-live'] = 'github.com/tylerb/gotype-live';

src/goMain.ts

@@ -32,6 +32,7 @@ import { clearCacheForTools } from './goPath';
 import { addTags, removeTags } from './goModifytags';
 import { parseLiveFile } from './goLiveErrors';
 import { GoCodeLensProvider } from './goCodelens';
+import { implCursor } from './goImpl';
 
 export let errorDiagnosticCollection: vscode.DiagnosticCollection;
 let warningDiagnosticCollection: vscode.DiagnosticCollection;
@@ -116,6 +117,10 @@ export function activate(ctx: vscode.ExtensionContext): void {
 		removeTags(args);
 	}));
 
+	ctx.subscriptions.push(vscode.commands.registerCommand('go.impl.cursor', () => {
+		implCursor();
+	}));
+
 	ctx.subscriptions.push(vscode.commands.registerCommand('go.test.cursor', (args) => {
 		let goConfig = vscode.workspace.getConfiguration('go');
 		testAtCursor(goConfig, args);