Stabilize simulator screen recording

Author: DjDeveloperr

cli/XCWSimctl.m

@@ -6,6 +6,7 @@
 #import "XCWPrivateSimulatorBooter.h"
 #import "XCWProcessRunner.h"
 
+#import <dispatch/dispatch.h>
 #import <errno.h>
 #import <math.h>
 #import <signal.h>
@@ -53,10 +54,47 @@ - (BOOL)installIPAAtPath:(NSString *)ipaPath simulatorUDID:(NSString *)udid erro
     return [value isKindOfClass:[NSString class]] ? value : @"";
 }
 
+static NSString *XCWTrimmedString(NSString *value) {
+    return [value stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceAndNewlineCharacterSet];
+}
+
 static NSNumber *XCWNumberValue(id value) {
     return [value isKindOfClass:[NSNumber class]] ? value : nil;
 }
 
+static NSString *XCWStringFromData(NSData *data) {
+    return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] ?: @"";
+}
+
+static NSData *XCWDataSnapshot(NSMutableData *data) {
+    @synchronized(data) {
+        return [data copy];
+    }
+}
+
+static void XCWAppendAvailableData(NSFileHandle *handle, NSMutableData *destination) {
+    @try {
+        NSData *chunk = [handle availableData];
+        if (chunk.length > 0) {
+            @synchronized(destination) {
+                [destination appendData:chunk];
+            }
+        }
+    } @catch (NSException *exception) {
+    }
+}
+
+static BOOL XCWWaitForTaskExit(NSTask *task, NSTimeInterval timeoutSeconds) {
+    NSDate *deadline = [NSDate dateWithTimeIntervalSinceNow:timeoutSeconds];
+    while (task.running && [deadline timeIntervalSinceNow] > 0) {
+        usleep(10 * 1000);
+    }
+    if (!task.running) {
+        return YES;
+    }
+    return NO;
+}
+
 static NSString * _Nullable XCWCreateTemporaryDirectory(NSString *prefix, NSError * _Nullable __autoreleasing *error) {
     NSString *templatePath = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"%@-XXXXXX", prefix]];
     char *directoryTemplate = strdup(templatePath.fileSystemRepresentation);
@@ -682,38 +720,136 @@ - (nullable NSData *)screenRecordingMP4ForSimulatorUDID:(NSString *)udid
 
     NSString *filename = [NSString stringWithFormat:@"simdeck-%@.mp4", NSUUID.UUID.UUIDString];
     NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:filename];
-    XCWProcessResult *result = [self.class runSimctl:@[
-        @"io",
-        udid,
-        @"recordVideo",
-        @"--codec=h264",
-        @"--force",
-        path,
-    ]
-                                          timeoutSec:durationSeconds
-                                       timeoutSignal:SIGINT
-                                               error:error];
-    if (result == nil) {
+    XCWProcessResult *resolvedSimctl = [XCWProcessRunner runLaunchPath:@"/usr/bin/xcrun"
+                                                             arguments:@[@"-f", @"simctl"]
+                                                             inputData:nil
+                                                                 error:error];
+    if (resolvedSimctl == nil) {
         [[NSFileManager defaultManager] removeItemAtPath:path error:nil];
         return nil;
     }
-
-    BOOL expectedStop = result.terminationStatus == 0 || result.terminationStatus == 124 || result.terminationStatus == 130;
-    if (expectedStop) {
-        NSData *data = [NSData dataWithContentsOfFile:path options:0 error:error];
+    NSString *simctlPath = XCWTrimmedString(XCWStringFromData(resolvedSimctl.stdoutData));
+    if (resolvedSimctl.terminationStatus != 0 || simctlPath.length == 0) {
         [[NSFileManager defaultManager] removeItemAtPath:path error:nil];
-        if (data.length > 0) {
-            return data;
+        if (error != NULL) {
+            NSString *message = resolvedSimctl.stderrString.length > 0 ? resolvedSimctl.stderrString : @"Unable to locate simctl.";
+            *error = [self.class errorWithDescription:message code:34];
         }
-        if (error != NULL && *error == nil) {
-            *error = [self.class errorWithDescription:@"Simulator screen recording command produced an empty MP4." code:34];
+        return nil;
+    }
+
+    NSTask *task = [[NSTask alloc] init];
+    task.launchPath = simctlPath;
+    task.arguments = @[@"io", udid, @"recordVideo", @"--codec=h264", @"--force", path];
+    task.standardInput = NSFileHandle.fileHandleWithNullDevice;
+    NSPipe *stdoutPipe = [NSPipe pipe];
+    NSPipe *stderrPipe = [NSPipe pipe];
+    task.standardOutput = stdoutPipe;
+    task.standardError = stderrPipe;
+
+    NSMutableData *stdoutData = [NSMutableData data];
+    NSMutableData *stderrData = [NSMutableData data];
+    NSFileHandle *stdoutHandle = stdoutPipe.fileHandleForReading;
+    NSFileHandle *stderrHandle = stderrPipe.fileHandleForReading;
+    dispatch_semaphore_t recordingStartedSemaphore = dispatch_semaphore_create(0);
+    __block BOOL recordingStarted = NO;
+
+    stdoutHandle.readabilityHandler = ^(NSFileHandle *handle) {
+        XCWAppendAvailableData(handle, stdoutData);
+    };
+    stderrHandle.readabilityHandler = ^(NSFileHandle *handle) {
+        @try {
+            NSData *chunk = [handle availableData];
+            if (chunk.length == 0) {
+                return;
+            }
+            BOOL shouldSignal = NO;
+            @synchronized(stderrData) {
+                [stderrData appendData:chunk];
+                NSString *text = XCWStringFromData(stderrData);
+                if (!recordingStarted && [text rangeOfString:@"Recording started"].location != NSNotFound) {
+                    recordingStarted = YES;
+                    shouldSignal = YES;
+                }
+            }
+            if (shouldSignal) {
+                dispatch_semaphore_signal(recordingStartedSemaphore);
+            }
+        } @catch (NSException *exception) {
+        }
+    };
+
+    NSError *launchError = nil;
+    if (![task launchAndReturnError:&launchError]) {
+        stdoutHandle.readabilityHandler = nil;
+        stderrHandle.readabilityHandler = nil;
+        [[NSFileManager defaultManager] removeItemAtPath:path error:nil];
+        if (error != NULL) {
+            *error = launchError ?: [self.class errorWithDescription:@"Unable to launch simulator screen recording." code:34];
         }
         return nil;
     }
 
+    NSTimeInterval startTimeout = MAX(10.0, MIN(30.0, durationSeconds + 10.0));
+    NSDate *startDeadline = [NSDate dateWithTimeIntervalSinceNow:startTimeout];
+    BOOL didStart = NO;
+    while ([startDeadline timeIntervalSinceNow] > 0) {
+        if (dispatch_semaphore_wait(recordingStartedSemaphore, DISPATCH_TIME_NOW) == 0) {
+            didStart = YES;
+            break;
+        }
+        if (!task.running) {
+            break;
+        }
+        usleep(10 * 1000);
+    }
+
+    if (didStart) {
+        NSDate *stopAt = [NSDate dateWithTimeIntervalSinceNow:durationSeconds];
+        while (task.running && [stopAt timeIntervalSinceNow] > 0) {
+            usleep(10 * 1000);
+        }
+    }
+    if (task.running) {
+        [task interrupt];
+    }
+    if (!XCWWaitForTaskExit(task, didStart ? 10.0 : 2.0) && task.running) {
+        [task terminate];
+        XCWWaitForTaskExit(task, 2.0);
+    }
+
+    stdoutHandle.readabilityHandler = nil;
+    stderrHandle.readabilityHandler = nil;
+    XCWAppendAvailableData(stdoutHandle, stdoutData);
+    XCWAppendAvailableData(stderrHandle, stderrData);
+
+    NSError *readError = nil;
+    NSData *data = nil;
+    NSDate *fileDeadline = [NSDate dateWithTimeIntervalSinceNow:2.0];
+    do {
+        data = [NSData dataWithContentsOfFile:path options:0 error:&readError];
+        if (data.length > 0) {
+            break;
+        }
+        usleep(50 * 1000);
+    } while ([fileDeadline timeIntervalSinceNow] > 0);
     [[NSFileManager defaultManager] removeItemAtPath:path error:nil];
+    if (data.length > 0) {
+        return data;
+    }
+
     if (error != NULL) {
-        *error = [self.class errorWithDescription:result.stderrString.length > 0 ? result.stderrString : @"Unable to record simulator screen." code:34];
+        NSString *stderrString = XCWStringFromData(XCWDataSnapshot(stderrData));
+        NSString *stdoutString = XCWStringFromData(XCWDataSnapshot(stdoutData));
+        NSString *details = stderrString.length > 0 ? stderrString : stdoutString;
+        if (!didStart && details.length == 0) {
+            details = @"Simulator screen recording did not start before the timeout.";
+        } else if (details.length == 0 && readError.localizedDescription.length > 0) {
+            details = readError.localizedDescription;
+        } else if (details.length == 0) {
+            details = @"Simulator screen recording command produced an empty MP4.";
+        }
+        *error = [self.class errorWithDescription:details code:34];
     }
     return nil;
 }