feat(prereqs): add Python module checks for Linux test prerequisites

src/e-test.js

@@ -7,6 +7,7 @@ const program = require('commander');
 const evmConfig = require('./evm-config');
 const { ensureNodeHeaders } = require('./utils/headers');
 const { color, fatal } = require('./utils/logging');
+const { ensureTestPrereqs } = require('./utils/prereqs');
 
 function runSpecRunner(config, script, runnerArgs) {
   const exec = process.execPath;
@@ -52,6 +53,9 @@ program
   )
   .action((specRunnerArgs, options) => {
     try {
+      // Check for required Python modules on Linux before running tests
+      ensureTestPrereqs();
+
       const config = evmConfig.current();
       if (options.node && options.nan) {
         fatal(

src/utils/prereqs.js

@@ -1,10 +1,28 @@
 const { execSync } = require('child_process');
-const { fatal } = require('./logging');
+const { color, fatal } = require('./logging');
 const semver = require('semver');
 
 const MINIMUM_PYTHON_VERSION = '3.9.0';
 const MINIMUM_NODEJS_VERSION = '22.12.0';
 
+/**
+ * Required Python modules for running Electron tests on Linux.
+ * These modules are needed for D-Bus mocking in the test suite.
+ * @see https://github.com/electron/build-tools/issues/790
+ */
+const LINUX_TEST_PYTHON_MODULES = [
+  {
+    name: 'dbusmock',
+    packageName: 'python-dbusmock',
+    description: 'D-Bus mock library for testing',
+  },
+  {
+    name: 'gi',
+    packageName: 'PyGObject',
+    description: 'Python GObject introspection bindings',
+  },
+];
+
 /**
  * Check if Python is installed and meets minimum version requirements
  * @returns {Object} Object with isValid boolean and version string
@@ -32,6 +50,48 @@ function checkPythonVersion() {
   return false;
 }
 
+/**
+ * Get the available Python command
+ * @returns {string|null} The Python command or null if not found
+ */
+function getPythonCommand() {
+  const pythonCommands = ['python3', 'python'];
+
+  for (const command of pythonCommands) {
+    try {
+      execSync(`${command} --version`, {
+        encoding: 'utf8',
+        stdio: 'pipe',
+      });
+      return command;
+    } catch (error) {
+      continue;
+    }
+  }
+
+  return null;
+}
+
+/**
+ * Check if a Python module is installed
+ * @param {string} moduleName - The name of the Python module to check
+ * @returns {boolean} True if the module is installed, false otherwise
+ */
+function checkPythonModule(moduleName) {
+  const pythonCmd = getPythonCommand();
+  if (!pythonCmd) return false;
+
+  try {
+    execSync(`${pythonCmd} -c "import ${moduleName}"`, {
+      encoding: 'utf8',
+      stdio: 'pipe',
+    });
+    return true;
+  } catch (error) {
+    return false;
+  }
+}
+
 /**
  * Check if Node.js is installed and meets minimum version requirements
  * @returns {Object} Object with isValid boolean and version string
@@ -74,6 +134,45 @@ function ensurePrereqs() {
   }
 }
 
+/**
+ * Ensure Python modules required for running Electron tests are installed.
+ * This check is only performed on Linux, as D-Bus mocking is Linux-specific.
+ * @see https://github.com/electron/build-tools/issues/790
+ */
+function ensureTestPrereqs() {
+  // D-Bus mocking is only required on Linux
+  if (process.platform !== 'linux') {
+    return;
+  }
+
+  const missingModules = [];
+
+  for (const module of LINUX_TEST_PYTHON_MODULES) {
+    if (!checkPythonModule(module.name)) {
+      missingModules.push(module);
+    }
+  }
+
+  if (missingModules.length > 0) {
+    const moduleList = missingModules
+      .map((m) => `  - ${color.cmd(m.packageName)} (${m.description})`)
+      .join('\n');
+
+    const installCmd = missingModules.map((m) => m.packageName).join(' ');
+
+    fatal(
+      `Missing Python modules required for running Electron tests on Linux:\n${moduleList}\n\n` +
+        `To install these modules, run:\n` +
+        `  ${color.cmd(`pip install ${installCmd}`)}\n\n` +
+        `Note: ${color.cmd('PyGObject')} may require system dependencies. On Fedora/RHEL:\n` +
+        `  ${color.cmd('sudo dnf install python3-devel gobject-introspection-devel cairo-gobject-devel')}\n` +
+        `On Ubuntu/Debian:\n` +
+        `  ${color.cmd('sudo apt install python3-dev libgirepository1.0-dev libcairo2-dev')}`,
+    );
+  }
+}
+
 module.exports = {
   ensurePrereqs,
+  ensureTestPrereqs,
 };

tests/prereqs.spec.mjs

@@ -0,0 +1,107 @@
+import { execSync } from 'child_process';
+import { beforeAll, afterAll, describe, expect, it, vi } from 'vitest';
+
+const { ensurePrereqs, ensureTestPrereqs } = require('../src/utils/prereqs');
+
+// Store original platform
+const originalPlatform = process.platform;
+
+/**
+ * Helper to mock process.platform
+ */
+function mockPlatform(platform) {
+  Object.defineProperty(process, 'platform', {
+    value: platform,
+    writable: true,
+    configurable: true,
+  });
+}
+
+/**
+ * Helper to restore process.platform
+ */
+function restorePlatform() {
+  Object.defineProperty(process, 'platform', {
+    value: originalPlatform,
+    writable: true,
+    configurable: true,
+  });
+}
+
+describe('prereqs', () => {
+  describe('ensureTestPrereqs', () => {
+    afterAll(() => {
+      restorePlatform();
+    });
+
+    it('should skip checks on non-Linux platforms', () => {
+      // Mock process.platform to be darwin (macOS)
+      mockPlatform('darwin');
+
+      // Should not throw on non-Linux
+      expect(() => ensureTestPrereqs()).not.toThrow();
+
+      // Mock process.platform to be win32 (Windows)
+      mockPlatform('win32');
+
+      // Should not throw on non-Linux
+      expect(() => ensureTestPrereqs()).not.toThrow();
+
+      restorePlatform();
+    });
+
+    it('should check for required Python modules on Linux', () => {
+      // Only run this test on Linux
+      if (originalPlatform !== 'linux') {
+        return;
+      }
+
+      // Check if dbusmock is available
+      let dbusmockAvailable = false;
+      try {
+        execSync('python3 -c "import dbusmock"', { stdio: 'pipe' });
+        dbusmockAvailable = true;
+      } catch {
+        dbusmockAvailable = false;
+      }
+
+      // Check if gi is available
+      let giAvailable = false;
+      try {
+        execSync('python3 -c "import gi"', { stdio: 'pipe' });
+        giAvailable = true;
+      } catch {
+        giAvailable = false;
+      }
+
+      // If both modules are available, ensureTestPrereqs should not throw
+      // If any module is missing, it should throw with a helpful message
+      if (dbusmockAvailable && giAvailable) {
+        expect(() => ensureTestPrereqs()).not.toThrow();
+      } else {
+        // We expect it to exit with a fatal error
+        // Since fatal calls process.exit, we need to mock it
+        const mockExit = vi.spyOn(process, 'exit').mockImplementation(() => {
+          throw new Error('process.exit called');
+        });
+        const mockError = vi.spyOn(console, 'error').mockImplementation(() => {});
+
+        expect(() => ensureTestPrereqs()).toThrow('process.exit called');
+
+        // Verify the error message contains helpful information
+        expect(mockError).toHaveBeenCalled();
+        const errorCall = mockError.mock.calls[0][0];
+
+        if (!dbusmockAvailable) {
+          expect(errorCall).toContain('python-dbusmock');
+        }
+        if (!giAvailable) {
+          expect(errorCall).toContain('PyGObject');
+        }
+
+        mockExit.mockRestore();
+        mockError.mockRestore();
+      }
+    });
+  });
+});