cmd/golsp/integration/vscode: add language server client for testing

We've been using https://github.com/stamblerre/vscode-test-golsp to test
the golsp. Ideally, we'd like to add integration tests with the major
editors, so we're moving this basic extension into x/tools, with the
intention of integration tests here. This is not meant to be used by any
users of golsp; it is only for testing.

Change-Id: I7c45e7c638311d29629ff6d3291332e68cf4621a
Reviewed-on: https://go-review.googlesource.com/c/153438
Reviewed-by: Ian Cottrell <iancottrell@google.com>

cmd/golsp/integration/vscode/.vscode/launch.json

@@ -0,0 +1,20 @@
+{
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Launch Extension",
+            "type": "extensionHost",
+            "request": "launch",
+            "runtimeExecutable": "${execPath}",
+            "args": [
+                "--extensionDevelopmentPath=${workspaceFolder}"
+            ],
+            "stopOnEntry": false,
+            "sourceMaps": true,
+            "outFiles": [
+                "${workspaceFolder}/out/**/*.js"
+            ],
+            "preLaunchTask": "npm"
+        },
+    ]
+}

cmd/golsp/integration/vscode/.vscode/tasks.json

@@ -0,0 +1,29 @@
+// Available variables which can be used inside of strings.
+// ${workspaceFolder}: the root folder of the team
+// ${file}: the current opened file
+// ${fileBasename}: the current opened file's basename
+// ${fileDirname}: the current opened file's dirname
+// ${fileExtname}: the current opened file's extension
+// ${cwd}: the current working directory of the spawned process
+// A task runner that calls the Typescript compiler (tsc) and
+// compiles the extension.
+{
+    "version": "2.0.0",
+    // we want to run npm
+    "command": "npm",
+    // the command is a shell script
+    "type": "shell",
+    // show the output window only if unrecognized errors occur.
+    "presentation": {
+        "reveal": "silent"
+    },
+    // we run the custom script "compile" as defined in package.json
+    "args": [
+        "run",
+        "compile"
+    ],
+    // The tsc compiler is started in watching mode
+    "isBackground": true,
+    // use the standard tsc in watch mode problem matcher to find compile problems in the output.
+    "problemMatcher": "$tsc-watch"
+}

cmd/golsp/integration/vscode/README.md

@@ -0,0 +1,21 @@
+# golsp testing extension
+
+An extension for debugging the Go Language Server provided by 
+https://golang.org/x/tools/cmd/golsp. The code for this extension comes from
+a combination of 
+https://github.com/Microsoft/vscode-extension-samples/blob/master/lsp-sample
+and https://github.com/Microsoft/vscode-go. 
+
+## Features
+
+* Diagnostics (on file change)
+* Completion (Ctrl + Space)
+* Jump to definition (F12 or right-click -> Go to Definition)
+* Signature help (Ctrl + Shift + Space)
+
+## Installation
+
+To package the extension, run `vsce package` from this directory. To install
+the extension, navigate to the "Extensions" panel in VSCode, and select
+"Install from VSIX..." from the menu in the top right corner. Choose the 
+`golsp-1.0.0.vsix file` and reload VSCode.

cmd/golsp/integration/vscode/package.json

@@ -0,0 +1,52 @@
+{
+    "name": "golsp",
+    "description": "Go Language Server Client for testing",
+    "author": "The Go authors",
+    "license": "SEE LICENSE IN ../../../../LICENSE",
+    "version": "1.0.0",
+    "repository": {
+        "type": "git",
+        "url": "https://golang.org/x/tools"
+    },
+    "publisher": "golang",
+    "engines": {
+        "vscode": "^1.23.0"
+    },
+    "activationEvents": [
+        "onLanguage:go"
+    ],
+    "main": "./out/extension",
+    "scripts": {
+        "vscode:prepublish": "tsc -p ./",
+        "compile": "tsc -watch -p ./",
+        "postinstall": "node ./node_modules/vscode/bin/install",
+        "lint": "node ./node_modules/tslint/bin/tslint ./src/*.ts"
+    },
+    "extensionDependencies": [],
+    "dependencies": {
+        "vscode-languageclient": "~4.3.0"
+    },
+    "devDependencies": {
+        "@types/mocha": "^5.2.5",
+        "@types/node": "^8.0.0",
+        "tslint": "^5.11.0",
+        "typescript": "^3.1.3",
+        "vscode": "^1.1.24"
+    },
+    "contributes": {
+        "configuration": {
+            "title": "Go LSP",
+            "properties": {
+                "golsp.flags": {
+                    "type": "array",
+                    "items": {
+                        "type": "string"
+                    },
+                    "default": [],
+                    "description": "Flags to pass to golsp",
+                    "scope": "resource"
+                }
+            }
+        }
+    }
+}

cmd/golsp/integration/vscode/src/extension.ts

@@ -0,0 +1,76 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+'use strict';
+
+import fs = require('fs');
+import lsp = require('vscode-languageclient');
+import vscode = require('vscode');
+import path = require('path');
+
+export function activate(ctx: vscode.ExtensionContext): void {
+  let document = vscode.window.activeTextEditor.document;
+  let config = vscode.workspace.getConfiguration('golsp', document.uri);
+  let golspFlags: string[] = config['flags'];
+  let serverOptions:
+      lsp.ServerOptions = {command: getBinPath('golsp'), args: golspFlags};
+  let clientOptions: lsp.LanguageClientOptions = {
+    initializationOptions: {},
+    documentSelector: ['go'],
+    uriConverters: {
+      code2Protocol: (uri: vscode.Uri): string =>
+          (uri.scheme ? uri : uri.with({scheme: 'file'})).toString(),
+      protocol2Code: (uri: string) => vscode.Uri.parse(uri),
+    },
+    revealOutputChannelOn: lsp.RevealOutputChannelOn.Never,
+  };
+  const c = new lsp.LanguageClient('golsp', serverOptions, clientOptions);
+  c.onReady().then(() => {
+    const capabilities = c.initializeResult && c.initializeResult.capabilities;
+    if (!capabilities) {
+      return vscode.window.showErrorMessage(
+          'The language server is not able to serve any features at the moment.');
+    }
+  });
+  ctx.subscriptions.push(c.start());
+}
+
+function getBinPath(toolName: string): string {
+  toolName = correctBinname(toolName);
+  let tool = findToolIn(toolName, 'PATH', false);
+  if (tool) {
+    return tool;
+  }
+  return findToolIn(toolName, 'GOPATH', true);
+}
+
+function findToolIn(
+    toolName: string, envVar: string, appendBinToPath: boolean): string {
+  let value = process.env[envVar];
+  if (value) {
+    let paths = value.split(path.delimiter);
+    for (let i = 0; i < paths.length; i++) {
+      let binpath = path.join(paths[i], appendBinToPath ? 'bin' : '', toolName);
+      if (fileExists(binpath)) {
+        return binpath;
+      }
+    }
+  }
+  return null;
+}
+
+function fileExists(filePath: string): boolean {
+  try {
+    return fs.statSync(filePath).isFile();
+  } catch (e) {
+    return false;
+  }
+}
+
+function correctBinname(toolName: string) {
+  if (process.platform === 'win32')
+    return toolName + '.exe';
+  else
+    return toolName;
+}

cmd/golsp/integration/vscode/tsconfig.json

@@ -0,0 +1,15 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "target": "es6",
+        "outDir": "out",
+        "rootDir": "src",
+        "lib": [
+            "es6"
+        ],
+        "sourceMap": true
+    },
+    "exclude": [
+        "node_modules"
+    ]
+}

cmd/golsp/integration/vscode/tslint.json

@@ -0,0 +1,12 @@
+{
+    "rules": {
+        "indent": [
+            true,
+            "tabs"
+        ],
+        "semicolon": [
+            true,
+            "always"
+        ]
+    }
+}