Add automatic platform detection from scheme build settings

When using session-set-defaults to configure a watchOS, tvOS, or visionOS
scheme, the simulator build tools (build_sim, build_run_sim, test_sim)
would incorrectly use "iOS Simulator" as the destination platform,
causing build failures with errors like:

  "Unable to find a device matching the provided destination specifier:
   { platform:iOS Simulator, OS:latest, name:Apple Watch Ultra 2 }"

This change adds automatic platform detection by querying the scheme's
build settings (SDKROOT and SUPPORTED_PLATFORMS) before building.
The detected platform is then used to construct the correct destination
string.

Changes:
- Add src/utils/platform-detection.ts with detectPlatformFromScheme()
- Integrate platform detection into build_sim, build_run_sim, test_sim
- Update tests to account for the additional platform detection call

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: jjfeiler

src/mcp/tools/simulator/__tests__/build_run_sim.test.ts

@@ -63,13 +63,19 @@ describe('build_run_sim tool', () => {
       const mockExecutor: CommandExecutor = async (command) => {
         callCount++;
         if (callCount === 1) {
-          // First call: build succeeds
+          // First call: platform detection succeeds
           return createMockCommandResponse({
             success: true,
-            output: 'BUILD SUCCEEDED',
+            output: 'SDKROOT = iphonesimulator\nSUPPORTED_PLATFORMS = iphonesimulator iphoneos',
           });
         } else if (callCount === 2) {
-          // Second call: showBuildSettings fails to get app path
+          // Second call: build succeeds
+          return createMockCommandResponse({
+            success: true,
+            output: 'BUILD SUCCEEDED',
+          });
+        } else if (callCount === 3) {
+          // Third call: showBuildSettings fails to get app path
           return createMockCommandResponse({
             success: false,
             error: 'Could not get build settings',
@@ -258,9 +264,13 @@ describe('build_run_sim tool', () => {
         trackingExecutor,
       );
 
-      // Should generate the initial build command
-      expect(callHistory).toHaveLength(1);
-      expect(callHistory[0].command).toEqual([
+      // Should generate two commands: platform detection + build
+      expect(callHistory).toHaveLength(2);
+      // First call is platform detection
+      expect(callHistory[0].command[0]).toBe('xcodebuild');
+      expect(callHistory[0].command).toContain('-showBuildSettings');
+      // Second call is the actual build
+      expect(callHistory[1].command).toEqual([
         'xcodebuild',
         '-workspace',
         '/path/to/MyProject.xcworkspace',
@@ -273,7 +283,7 @@ describe('build_run_sim tool', () => {
         'platform=iOS Simulator,name=iPhone 16,OS=latest',
         'build',
       ]);
-      expect(callHistory[0].logPrefix).toBe('iOS Simulator Build');
+      expect(callHistory[1].logPrefix).toBe('iOS Simulator Build');
     });
 
     it('should generate correct build command after finding simulator', async () => {
@@ -285,26 +295,16 @@ describe('build_run_sim tool', () => {
       }> = [];
 
       let callCount = 0;
-      // Create tracking executor that succeeds on first call (list) and fails on second
+      // Create tracking executor: platform detection, then build (fails)
       const trackingExecutor: CommandExecutor = async (command, logPrefix, useShell, opts) => {
         callHistory.push({ command, logPrefix, useShell, opts });
         callCount++;
 
         if (callCount === 1) {
-          // First call: simulator list succeeds
+          // First call: platform detection succeeds
           return createMockCommandResponse({
             success: true,
-            output: JSON.stringify({
-              devices: {
-                'iOS 16.0': [
-                  {
-                    udid: 'test-uuid-123',
-                    name: 'iPhone 16',
-                    state: 'Booted',
-                  },
-                ],
-              },
-            }),
+            output: 'SDKROOT = iphonesimulator\nSUPPORTED_PLATFORMS = iphonesimulator iphoneos',
             error: undefined,
           });
         } else {
@@ -326,39 +326,29 @@ describe('build_run_sim tool', () => {
         trackingExecutor,
       );
 
-      // Should generate build command and then build settings command
+      // Should generate platform detection and then build command
       expect(callHistory).toHaveLength(2);
 
-      // First call: build command
-      expect(callHistory[0].command).toEqual([
-        'xcodebuild',
-        '-workspace',
-        '/path/to/MyProject.xcworkspace',
-        '-scheme',
-        'MyScheme',
-        '-configuration',
-        'Debug',
-        '-skipMacroValidation',
-        '-destination',
-        'platform=iOS Simulator,name=iPhone 16,OS=latest',
-        'build',
-      ]);
-      expect(callHistory[0].logPrefix).toBe('iOS Simulator Build');
+      // First call: platform detection
+      expect(callHistory[0].command[0]).toBe('xcodebuild');
+      expect(callHistory[0].command).toContain('-showBuildSettings');
+      expect(callHistory[0].logPrefix).toBe('Platform Detection');
 
-      // Second call: build settings command to get app path
+      // Second call: build command (which fails)
       expect(callHistory[1].command).toEqual([
         'xcodebuild',
-        '-showBuildSettings',
         '-workspace',
         '/path/to/MyProject.xcworkspace',
         '-scheme',
         'MyScheme',
         '-configuration',
         'Debug',
+        '-skipMacroValidation',
         '-destination',
         'platform=iOS Simulator,name=iPhone 16,OS=latest',
+        'build',
       ]);
-      expect(callHistory[1].logPrefix).toBe('Get App Path');
+      expect(callHistory[1].logPrefix).toBe('iOS Simulator Build');
     });
 
     it('should generate correct build settings command after successful build', async () => {
@@ -370,26 +360,16 @@ describe('build_run_sim tool', () => {
       }> = [];
 
       let callCount = 0;
-      // Create tracking executor that succeeds on first two calls and fails on third
+      // Create tracking executor: platform detection, build, then build settings for app path
       const trackingExecutor: CommandExecutor = async (command, logPrefix, useShell, opts) => {
         callHistory.push({ command, logPrefix, useShell, opts });
         callCount++;
 
         if (callCount === 1) {
-          // First call: simulator list succeeds
+          // First call: platform detection succeeds
           return createMockCommandResponse({
             success: true,
-            output: JSON.stringify({
-              devices: {
-                'iOS 16.0': [
-                  {
-                    udid: 'test-uuid-123',
-                    name: 'iPhone 16',
-                    state: 'Booted',
-                  },
-                ],
-              },
-            }),
+            output: 'SDKROOT = iphonesimulator\nSUPPORTED_PLATFORMS = iphonesimulator iphoneos',
             error: undefined,
           });
         } else if (callCount === 2) {
@@ -420,11 +400,16 @@ describe('build_run_sim tool', () => {
         trackingExecutor,
       );
 
-      // Should generate build command and build settings command
-      expect(callHistory).toHaveLength(2);
+      // Should generate platform detection, build command, and build settings command
+      expect(callHistory).toHaveLength(3);
+
+      // First call: platform detection
+      expect(callHistory[0].command[0]).toBe('xcodebuild');
+      expect(callHistory[0].command).toContain('-showBuildSettings');
+      expect(callHistory[0].logPrefix).toBe('Platform Detection');
 
-      // First call: build command
-      expect(callHistory[0].command).toEqual([
+      // Second call: build command
+      expect(callHistory[1].command).toEqual([
         'xcodebuild',
         '-workspace',
         '/path/to/MyProject.xcworkspace',
@@ -437,10 +422,10 @@ describe('build_run_sim tool', () => {
         'platform=iOS Simulator,name=iPhone 16',
         'build',
       ]);
-      expect(callHistory[0].logPrefix).toBe('iOS Simulator Build');
+      expect(callHistory[1].logPrefix).toBe('iOS Simulator Build');
 
-      // Second call: build settings command
-      expect(callHistory[1].command).toEqual([
+      // Third call: build settings command for app path
+      expect(callHistory[2].command).toEqual([
         'xcodebuild',
         '-showBuildSettings',
         '-workspace',
@@ -452,7 +437,7 @@ describe('build_run_sim tool', () => {
         '-destination',
         'platform=iOS Simulator,name=iPhone 16',
       ]);
-      expect(callHistory[1].logPrefix).toBe('Get App Path');
+      expect(callHistory[2].logPrefix).toBe('Get App Path');
     });
 
     it('should handle paths with spaces in command generation', async () => {
@@ -482,9 +467,13 @@ describe('build_run_sim tool', () => {
         trackingExecutor,
       );
 
-      // Should generate build command first
-      expect(callHistory).toHaveLength(1);
-      expect(callHistory[0].command).toEqual([
+      // Should generate two commands: platform detection + build
+      expect(callHistory).toHaveLength(2);
+      // First call is platform detection
+      expect(callHistory[0].command[0]).toBe('xcodebuild');
+      expect(callHistory[0].command).toContain('-showBuildSettings');
+      // Second call is the actual build with paths containing spaces
+      expect(callHistory[1].command).toEqual([
         'xcodebuild',
         '-workspace',
         '/Users/dev/My Project/MyProject.xcworkspace',
@@ -497,7 +486,7 @@ describe('build_run_sim tool', () => {
         'platform=iOS Simulator,name=iPhone 16 Pro,OS=latest',
         'build',
       ]);
-      expect(callHistory[0].logPrefix).toBe('iOS Simulator Build');
+      expect(callHistory[1].logPrefix).toBe('iOS Simulator Build');
     });
   });
 

src/mcp/tools/simulator/__tests__/build_sim.test.ts

@@ -217,9 +217,13 @@ describe('build_sim tool', () => {
         trackingExecutor,
       );
 
-      // Should generate one build command
-      expect(callHistory).toHaveLength(1);
-      expect(callHistory[0].command).toEqual([
+      // Should generate two commands: platform detection + build
+      expect(callHistory).toHaveLength(2);
+      // First call is platform detection
+      expect(callHistory[0].command[0]).toBe('xcodebuild');
+      expect(callHistory[0].command).toContain('-showBuildSettings');
+      // Second call is the actual build
+      expect(callHistory[1].command).toEqual([
         'xcodebuild',
         '-workspace',
         '/path/to/MyProject.xcworkspace',
@@ -232,7 +236,7 @@ describe('build_sim tool', () => {
         'platform=iOS Simulator,name=iPhone 16,OS=latest',
         'build',
       ]);
-      expect(callHistory[0].logPrefix).toBe('iOS Simulator Build');
+      expect(callHistory[1].logPrefix).toBe('iOS Simulator Build');
     });
 
     it('should generate correct build command with minimal parameters (project)', async () => {
@@ -262,9 +266,13 @@ describe('build_sim tool', () => {
         trackingExecutor,
       );
 
-      // Should generate one build command
-      expect(callHistory).toHaveLength(1);
-      expect(callHistory[0].command).toEqual([
+      // Should generate two commands: platform detection + build
+      expect(callHistory).toHaveLength(2);
+      // First call is platform detection
+      expect(callHistory[0].command[0]).toBe('xcodebuild');
+      expect(callHistory[0].command).toContain('-showBuildSettings');
+      // Second call is the actual build
+      expect(callHistory[1].command).toEqual([
         'xcodebuild',
         '-project',
         '/path/to/MyProject.xcodeproj',
@@ -277,7 +285,7 @@ describe('build_sim tool', () => {
         'platform=iOS Simulator,name=iPhone 16,OS=latest',
         'build',
       ]);
-      expect(callHistory[0].logPrefix).toBe('iOS Simulator Build');
+      expect(callHistory[1].logPrefix).toBe('iOS Simulator Build');
     });
 
     it('should generate correct build command with all optional parameters', async () => {
@@ -311,9 +319,13 @@ describe('build_sim tool', () => {
         trackingExecutor,
       );
 
-      // Should generate one build command with all parameters
-      expect(callHistory).toHaveLength(1);
-      expect(callHistory[0].command).toEqual([
+      // Should generate two commands: platform detection + build
+      expect(callHistory).toHaveLength(2);
+      // First call is platform detection
+      expect(callHistory[0].command[0]).toBe('xcodebuild');
+      expect(callHistory[0].command).toContain('-showBuildSettings');
+      // Second call is the actual build with all parameters
+      expect(callHistory[1].command).toEqual([
         'xcodebuild',
         '-workspace',
         '/path/to/MyProject.xcworkspace',
@@ -329,7 +341,7 @@ describe('build_sim tool', () => {
         '--verbose',
         'build',
       ]);
-      expect(callHistory[0].logPrefix).toBe('iOS Simulator Build');
+      expect(callHistory[1].logPrefix).toBe('iOS Simulator Build');
     });
 
     it('should handle paths with spaces in command generation', async () => {
@@ -359,9 +371,13 @@ describe('build_sim tool', () => {
         trackingExecutor,
       );
 
-      // Should generate one build command with paths containing spaces
-      expect(callHistory).toHaveLength(1);
-      expect(callHistory[0].command).toEqual([
+      // Should generate two commands: platform detection + build
+      expect(callHistory).toHaveLength(2);
+      // First call is platform detection
+      expect(callHistory[0].command[0]).toBe('xcodebuild');
+      expect(callHistory[0].command).toContain('-showBuildSettings');
+      // Second call is the actual build with paths containing spaces
+      expect(callHistory[1].command).toEqual([
         'xcodebuild',
         '-workspace',
         '/Users/dev/My Project/MyProject.xcworkspace',
@@ -374,7 +390,7 @@ describe('build_sim tool', () => {
         'platform=iOS Simulator,name=iPhone 16 Pro,OS=latest',
         'build',
       ]);
-      expect(callHistory[0].logPrefix).toBe('iOS Simulator Build');
+      expect(callHistory[1].logPrefix).toBe('iOS Simulator Build');
     });
 
     it('should generate correct build command with useLatestOS set to true', async () => {
@@ -405,9 +421,13 @@ describe('build_sim tool', () => {
         trackingExecutor,
       );
 
-      // Should generate one build command with OS=latest
-      expect(callHistory).toHaveLength(1);
-      expect(callHistory[0].command).toEqual([
+      // Should generate two commands: platform detection + build
+      expect(callHistory).toHaveLength(2);
+      // First call is platform detection
+      expect(callHistory[0].command[0]).toBe('xcodebuild');
+      expect(callHistory[0].command).toContain('-showBuildSettings');
+      // Second call is the actual build with OS=latest
+      expect(callHistory[1].command).toEqual([
         'xcodebuild',
         '-workspace',
         '/path/to/MyProject.xcworkspace',
@@ -420,7 +440,7 @@ describe('build_sim tool', () => {
         'platform=iOS Simulator,name=iPhone 16,OS=latest',
         'build',
       ]);
-      expect(callHistory[0].logPrefix).toBe('iOS Simulator Build');
+      expect(callHistory[1].logPrefix).toBe('iOS Simulator Build');
     });
   });