Fix "Cannot set properties of undefined" error in validated() method when credentials are missing (#170)

This PR fixes a critical issue where the plugin would crash with `Cannot
set properties of undefined (setting 'installId')` when the homebridge
config file didn't have a properly initialized `credentials` object for
the August platform.

## Problem

The error occurred in the `validated()` method when trying to set
properties on `pluginConfig.credentials`:

```typescript
pluginConfig.credentials.installId = this.config.credentials?.installId
```

This happened because:
1. When `credentials` was completely missing from the config file, it
would be `undefined`
2. When `credentials` was explicitly set to `null`, the existing check
`typeof pluginConfig.credentials !== 'object'` would pass (since `typeof
null === 'object'` in JavaScript), but then trying to set properties on
`null` would fail

## Solution

Updated the `pluginConfig()` method to properly handle both `null` and
`undefined` credentials:

```typescript
// Before: Only checked for non-object types
if (typeof pluginConfig.credentials !== 'object') {
  throw new TypeError('pluginConfig.credentials is not an object')
}

// After: Explicitly check for null and undefined, then initialize
if (typeof pluginConfig.credentials !== 'object' || pluginConfig.credentials === null) {
  pluginConfig.credentials = {}
}
```

Now when the `validated()` method runs, it can safely set properties on
`pluginConfig.credentials` because the object is guaranteed to exist.

## Testing

Added comprehensive tests to verify:
- Undefined credentials in config file are handled gracefully
- Null credentials in config file are handled gracefully  
- The credentials object is properly initialized and the installId is
saved

All existing tests continue to pass, ensuring no regressions.

Fixes #169.

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---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: Donavan Becker <[email protected]>
Co-authored-by: donavanbecker <[email protected]>

Author: Copilot

src/platform.test.ts

@@ -8,10 +8,18 @@ import type { AugustPlatformConfig } from './settings.js'
 
 // Mock august-yale module
 vi.mock('august-yale', () => {
+  const MockAugust = vi.fn().mockImplementation(() => ({
+    end: vi.fn(),
+  }))
+  
+  // Type assertion to add static methods
+  const MockConstructor = MockAugust as any
+  MockConstructor.details = vi.fn()
+  MockConstructor.authorize = vi.fn()
+  MockConstructor.validate = vi.fn()
+  
   return {
-    default: {
-      details: vi.fn(),
-    },
+    default: MockConstructor,
   }
 })
 
@@ -167,4 +175,74 @@ describe('AugustPlatform', () => {
       expect(lockSpy).toHaveBeenCalledWith([mockDevice])
     })
   })
+
+  describe('validated method', () => {
+    it('should handle undefined credentials in config file gracefully', async () => {
+      // Mock config file with undefined credentials
+      const mockConfigFile = {
+        platforms: [
+          {
+            platform: 'August',
+            name: 'Test August',
+            // credentials is undefined here
+          },
+        ],
+      }
+
+      vi.mocked(readFileSync).mockReturnValue(JSON.stringify(mockConfigFile))
+
+      platform = new AugustPlatform(mockLog, mockConfig, mockApi)
+
+      // This should not throw an error when trying to set installId
+      await expect(platform.validated()).resolves.toBeUndefined()
+    })
+
+    it('should handle null credentials in config file gracefully', async () => {
+      // Mock config file with null credentials
+      const mockConfigFile = {
+        platforms: [
+          {
+            platform: 'August',
+            name: 'Test August',
+            credentials: null,
+          },
+        ],
+      }
+
+      vi.mocked(readFileSync).mockReturnValue(JSON.stringify(mockConfigFile))
+
+      platform = new AugustPlatform(mockLog, mockConfig, mockApi)
+
+      // This should not throw an error when trying to set installId
+      await expect(platform.validated()).resolves.toBeUndefined()
+    })
+
+    it('should initialize credentials object and save installId when credentials are missing', async () => {
+      // Mock config file with undefined credentials
+      const mockConfigFile = {
+        platforms: [
+          {
+            platform: 'August',
+            name: 'Test August',
+            // credentials is undefined here
+          },
+        ],
+      }
+
+      vi.mocked(readFileSync).mockReturnValue(JSON.stringify(mockConfigFile))
+
+      platform = new AugustPlatform(mockLog, mockConfig, mockApi)
+
+      await platform.validated()
+
+      // Verify that writeFileSync was called (meaning the config was updated)
+      expect(writeFileSync).toHaveBeenCalled()
+
+      // Verify the credentials object was created and populated
+      const writeCall = vi.mocked(writeFileSync).mock.calls[0]
+      const savedConfig = JSON.parse(writeCall[1] as string)
+      expect(savedConfig.platforms[0].credentials).toBeDefined()
+      expect(savedConfig.platforms[0].credentials.installId).toBeDefined()
+    })
+  })
 })

src/platform.ts

@@ -225,8 +225,10 @@ export class AugustPlatform implements DynamicPlatformPlugin {
       throw new Error(`Cannot find config for ${PLATFORM_NAME} in platforms array`)
     }
     // check the .credentials is an object before doing object things with it
-    if (typeof pluginConfig.credentials !== 'object') {
-      throw new TypeError('pluginConfig.credentials is not an object')
+    // Note: typeof null === 'object' is true, so we need to explicitly check for null and undefined
+    if (typeof pluginConfig.credentials !== 'object' || pluginConfig.credentials === null) {
+      // Initialize credentials as an empty object if it doesn't exist or is null
+      pluginConfig.credentials = {}
     }
     return { pluginConfig, currentConfig }
   }