Pass site_config as an optional arg.

This change passes a path to a site_config into vite.js's proxyOptions
so callers that don't have a standard `sites/` layout (eg frappe press
dashboard - potentially any caller using frappe-ui as a lib) can
configure the `webserver_port`.

Also includes basic node test run via `node --test`.

vite.js

@@ -4,8 +4,15 @@ const fs = require('fs')
 module.exports = function proxyOptions({
   port = 8080,
   source = '^/(app|login|api|assets|files)',
- } = {}) {
-  const config = getCommonSiteConfig()
+  site_config_path = null,
+} = {}) {
+  const config = site_config_path ?
+    (
+      JSON.parse(fs.readFileSync(site_config_path))
+    ) :
+    (
+      getCommonSiteConfig()
+    )
   const webserver_port = config ? config.webserver_port : 8000
   if (!config) {
     console.log('No common_site_config.json found, using default port 8000')

vite.test.js

@@ -0,0 +1,62 @@
+const { describe, it, afterEach, beforeEach } = require('node:test')
+const frappeui = require('./vite.js')
+const fs = require('fs/promises')
+const path = require('path')
+const assert = require('assert')
+const os = require('os')
+
+
+describe('Test site_config resolution', () => {
+
+  let tmpDir
+  let site_config_path
+  let cwd
+  const jsonData = { webserver_port: "1001" }
+  const proxySource = '^/(app|login|api|assets|files)'
+  const localhostTarget = 'http://127.0.0.1'
+
+  beforeEach(async () => {
+    dirPath = path.join(os.tmpdir(), ts())
+    tmpDir = await fs.mkdtemp(dirPath)
+    await fs.mkdir(path.join(tmpDir, 'sites'))
+    await fs.mkdir(path.join(tmpDir, 'apps'))
+    const sitesDir = path.join(tmpDir, 'sites')
+    scp = path.join(sitesDir, 'common_site_config.json')
+    await fs.writeFile(scp, JSON.stringify(jsonData), 'utf8')
+
+    // TODO: avoid chdir in tests. Unfortunately the code under test uses 
+    // relative paths, and changing that will need a bigger change than 
+    // simply doing this. 
+    cwd = process.cwd()
+    process.chdir(sitesDir)
+  })
+
+  afterEach(async () => {
+    process.chdir(cwd)
+    await fs.rm(tmpDir, { recursive: true })
+  })
+
+  it('should find commmon_site_config.json', () => {
+    site_config = frappeui()
+    got_target = site_config.config().server.proxy[proxySource].target
+    want_target = localhostTarget + ':' + jsonData.webserver_port
+    assert.ok(got_target == want_target)
+  })
+
+  it('should read the provided commmon_site_config.json', async () => {
+    let testConfigPath = path.join(tmpDir, 'test.json')
+    let testConfig = { webserver_port: "1002" }
+    await fs.writeFile(testConfigPath, JSON.stringify(testConfig), 'utf8')
+
+    site_config = frappeui({ site_config_path: testConfigPath })
+    got_target = site_config.config().server.proxy[proxySource].target
+    want_target = localhostTarget + ':' + testConfig.webserver_port
+    assert.ok(got_target == want_target)
+  })
+})
+
+function ts() {
+  const now = new Date();
+  const ts = now.toISOString().replace(/[-:]/g, '')
+  return ts
+}