fix: open URL in browser on WSL (#128)

Here's a more elegant solution for opening URLs from WSL in your
favorite browser. It is based on `sensible-browser` which is included in
the default distribution for WSL. This avoids issues with the WSL
environment, `cmd.exe`. quoting parameters, etc.

In WSL, set the default browser using the `BROWSER` variable, for
example,

```sh
export BROWSER="/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome.exe"
or
export BROWSER="/mnt/c/Program Files (x86)/Microsoft/Edge/Application/msedge.exe"
```

Note: To permanently set the default browser, add the appropriate entry
to your shell's RC file, e.g. .bashrc or .zshrc.

To launch a URL from the WSL command line:

```sh
sensible-browser https://google.com
```

To launch a URL using `promise-spawn`:

```js
const promiseSpawn = require('@npmcli/promise-spawn')
promiseSpawn.open('https://google.com')
```

Replaces #118
Closes #62

### Test

```
os: 5.15.153.1-microsoft-standard-WSL2
node: 20.18.0
npm: 10.8.2
```


![image](https://github.com/user-attachments/assets/899801c5-6f05-477e-92c7-f2669526fa03)

---------

Co-authored-by: Gar <wraithgar@github.com>

lib/index.js

@@ -131,9 +131,19 @@ const open = (_args, opts = {}, extra = {}) => {
 
   let platform = process.platform
   // process.platform === 'linux' may actually indicate WSL, if that's the case
-  // we want to treat things as win32 anyway so the host can open the argument
+  // open the argument with sensible-browser which is pre-installed
+  // In WSL, set the default browser using, for example,
+  // export BROWSER="/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome.exe"
+  // or
+  // export BROWSER="/mnt/c/Program Files (x86)/Microsoft/Edge/Application/msedge.exe"
+  // To permanently set the default browser, add the appropriate entry to your shell's
+  // RC file, e.g. .bashrc or .zshrc.
   if (platform === 'linux' && os.release().toLowerCase().includes('microsoft')) {
-    platform = 'win32'
+    platform = 'wsl'
+    if (!process.env.BROWSER) {
+      return Promise.reject(
+        new Error('Set the BROWSER environment variable to your desired browser.'))
+    }
   }
 
   let command = options.command
@@ -146,6 +156,8 @@ const open = (_args, opts = {}, extra = {}) => {
       // accidentally interpret the first arg as the title, we stick an empty
       // string immediately after the start command
       command = 'start ""'
+    } else if (platform === 'wsl') {
+      command = 'sensible-browser'
     } else if (platform === 'darwin') {
       command = 'open'
     } else {

test/open.js

@@ -2,6 +2,7 @@
 
 const spawk = require('spawk')
 const t = require('tap')
+const os = require('node:os')
 
 const promiseSpawn = require('../lib/index.js')
 
@@ -10,6 +11,8 @@ t.afterEach(() => {
   spawk.clean()
 })
 
+const isWSL = process.platform === 'linux' && os.release().toLowerCase().includes('microsoft')
+
 t.test('process.platform === win32', (t) => {
   const comSpec = process.env.ComSpec
   const platformDesc = Object.getOwnPropertyDescriptor(process, 'platform')
@@ -118,7 +121,8 @@ t.test('process.platform === linux', (t) => {
     Object.defineProperty(process, 'platform', platformDesc)
   })
 
-  t.test('uses xdg-open in a shell', async (t) => {
+  // xdg-open is not installed in WSL by default
+  t.test('uses xdg-open in a shell', { skip: isWSL }, async (t) => {
     const proc = spawk.spawn('sh', ['-c', 'xdg-open https://google.com'], { shell: false })
 
     const result = await promiseSpawn.open('https://google.com')
@@ -130,7 +134,8 @@ t.test('process.platform === linux', (t) => {
     t.ok(proc.called)
   })
 
-  t.test('ignores shell = false', async (t) => {
+  // xdg-open is not installed in WSL by default
+  t.test('ignores shell = false', { skip: isWSL }, async (t) => {
     const proc = spawk.spawn('sh', ['-c', 'xdg-open https://google.com'], { shell: false })
 
     const result = await promiseSpawn.open('https://google.com', { shell: false })
@@ -154,58 +159,76 @@ t.test('process.platform === linux', (t) => {
     t.ok(proc.called)
   })
 
-  t.test('when os.release() includes Microsoft treats as win32', async (t) => {
-    const comSpec = process.env.ComSpec
-    process.env.ComSpec = 'C:\\Windows\\System32\\cmd.exe'
-    t.teardown(() => {
-      process.env.ComSPec = comSpec
-    })
-
+  t.test('when os.release() includes Microsoft treats as WSL', async (t) => {
     const promiseSpawnMock = t.mock('../lib/index.js', {
       os: {
         release: () => 'Microsoft',
       },
     })
+    const browser = process.env.BROWSER
+    process.env.BROWSER = '/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome.exe'
 
-    const proc = spawk.spawn('C:\\Windows\\System32\\cmd.exe',
-      ['/d', '/s', '/c', 'start "" https://google.com'],
-      { shell: false })
+    const proc = spawk.spawn('sh', ['-c', 'sensible-browser https://google.com'], { shell: false })
 
     const result = await promiseSpawnMock.open('https://google.com')
     t.hasStrict(result, {
       code: 0,
       signal: undefined,
     })
 
-    t.ok(proc.called)
-  })
-
-  t.test('when os.release() includes microsoft treats as win32', async (t) => {
-    const comSpec = process.env.ComSpec
-    process.env.ComSpec = 'C:\\Windows\\System32\\cmd.exe'
     t.teardown(() => {
-      process.env.ComSPec = comSpec
+      process.env.BROWSER = browser
     })
 
+    t.ok(proc.called)
+  })
+
+  t.test('when os.release() includes microsoft treats as WSL', async (t) => {
     const promiseSpawnMock = t.mock('../lib/index.js', {
       os: {
         release: () => 'microsoft',
       },
     })
+    const browser = process.env.BROWSER
+    process.env.BROWSER = '/mnt/c/Program Files (x86)/Google/Chrome/Application/chrome.exe'
 
-    const proc = spawk.spawn('C:\\Windows\\System32\\cmd.exe',
-      ['/d', '/s', '/c', 'start "" https://google.com'],
-      { shell: false })
+    const proc = spawk.spawn('sh', ['-c', 'sensible-browser https://google.com'], { shell: false })
 
     const result = await promiseSpawnMock.open('https://google.com')
     t.hasStrict(result, {
       code: 0,
       signal: undefined,
     })
 
+    t.teardown(() => {
+      process.env.BROWSER = browser
+    })
+
     t.ok(proc.called)
   })
 
+  t.test('fails on WSL if BROWSER is not set', async (t) => {
+    const promiseSpawnMock = t.mock('../lib/index.js', {
+      os: {
+        release: () => 'microsoft',
+      },
+    })
+    const browser = process.env.BROWSER
+    delete process.env.BROWSER
+
+    const proc = spawk.spawn('sh', ['-c', 'sensible-browser https://google.com'], { shell: false })
+
+    await t.rejects(promiseSpawnMock.open('https://google.com'), {
+      message: 'Set the BROWSER environment variable to your desired browser.',
+    })
+
+    t.teardown(() => {
+      process.env.BROWSER = browser
+    })
+
+    t.notOk(proc.called)
+  })
+
   t.end()
 })