Synchronize access to route singletons

[julianlocke]

Makes objective-c route singleton access thread safe by synchronizing over a lock object per file. This has been live in our production iOS app for a week without incident. Example output:

static NSObject *lockObj = nil;
+ (void)initialize {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    lockObj = [[NSObject alloc] init];
  });
}

+ (DBRoute *)DBACCOUNTAppleLogin {
  @synchronized(lockObj) {
    if (!DBACCOUNTAppleLogin) {
      DBACCOUNTAppleLogin =
          [[DBRoute alloc] init:@"apple_login"
                           namespace_:@"account"
                           deprecated:@NO
                           resultType:[DBACCOUNTAppleLoginResult class]
                            errorType:[DBACCOUNTAppleLoginError class]
                                attrs:@{
                                  @"auth" : @"app",
                                  @"host" : @"api",
                                  @"style" : @"rpc"
                                }
                dataStructSerialBlock:nil
              dataStructDeserialBlock:nil];
    }
    return DBACCOUNTAppleLogin;
  }
}

+ (DBRoute *)DBACCOUNTAppleSignup {
  @synchronized(lockObj) {
    if (!DBACCOUNTAppleSignup) {
      DBACCOUNTAppleSignup =
          [[DBRoute alloc] init:@"apple_signup"
                           namespace_:@"account"
                           deprecated:@NO
                           resultType:[DBACCOUNTAppleSignupResult class]
                            errorType:[DBACCOUNTAppleSignupError class]
                                attrs:@{
                                  @"auth" : @"app",
                                  @"host" : @"api",
                                  @"style" : @"rpc"
                                }
                dataStructSerialBlock:nil
              dataStructDeserialBlock:nil];
    }
    return DBACCOUNTAppleSignup;
  }
}
... etc.

General Contributing

• Have you read the Code of Conduct and signed the CLA?

Is This a Code Change?

• Non-code related change (markdown/git settings etc)
• Code Change
• Example/Test Code Change

Validation

• Have you ran tox?
• Do the tests pass?

[codecov]

Codecov Report

Merging #248 (43898e6) into main (b0e5ae1) will decrease coverage by 0.04%.
The diff coverage is 5.71%.

@@            Coverage Diff             @@
##             main     #248      +/-   ##
==========================================
- Coverage   51.65%   51.60%   -0.05%     
==========================================
  Files          37       37              
  Lines        8393     8400       +7     
  Branches     1790     1790              
==========================================
  Hits         4335     4335              
- Misses       3744     3751       +7     
  Partials      314      314              

Flag	Coverage Δ
unit	51.60% <5.71%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
stone/backends/obj_c_types.py	0.00% <0.00%> (ø)
stone/backends/python_rsrc/stone_validators.py	87.84% <ø> (ø)
stone/backends/swift.py	0.00% <ø> (ø)
stone/backends/swift_helpers.py	0.00% <0.00%> (ø)
stone/backends/swift_types.py	0.00% <0.00%> (ø)
stone/backends/tsd_client.py	55.31% <0.00%> (ø)
stone/backends/tsd_types.py	37.91% <0.00%> (ø)
stone/cli.py	0.00% <0.00%> (ø)
stone/frontend/parser.py	92.04% <0.00%> (ø)
stone/backend.py	83.07% <100.00%> (ø)
... and 1 more

---

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[YufeiG]

lgtm