Fixing version comparison & adding support for build comparisons

[pudquick]

This is both a bug fix and a new feature.

First the bug fix - here's an example situation:

• expectedVersion set to: 10.14.3
• systemVersion read as: 10.15.1

This logic: https://github.com/google/macops/blob/master/deprecation_notifier/DeprecationNotifier/DNAppDelegate.m#L60-L63

  } else if (([expectedVersionArray[0] intValue] <= [systemVersionArray[0] intValue]) &&
             ([expectedVersionArray[1] intValue] <= [systemVersionArray[1] intValue]) &&
             ([expectedVersionArray[2] intValue] <= [systemVersionArray[2] intValue])) {
    NSLog(@"Exiting: OS is already %@ or greater", expectedVersion);

10 <= 10: true
14 <= 15: true
3 <= 1: false

The comparison will fail when it shouldn't.

This PR includes better comparison logic.

It additionally adds support for a new optional Localizable string value: expectedBuilds

The value of this string should be a comma delimited string (no spaces) of allowed builds.

If the OS is detected to be exactly the expectedVersion, then:

• if no expectedBuilds is defined, Deprecation Notifier will determine the OS meets the requirement
• if expectedBuilds is defined, the system build is looked for in expectedBuilds - if and only if the build is present, then the OS meets the requirement

Use case: for environments that are supporting a major OS version which has now gone into Security Updates, Deprecation Notifier is unable to tell a "fully patched" OS version without looking at the build information.

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[pudquick]

I signed it!

[googlebot]

CLAs look good, thanks!

[russellhancox]

This logic, while correct, is a bit more difficult to read as it's quite repetitive. Could we flip it around?

if ([expectedVersionArray isEqualToArray:systemVersionArray]) {
  NSLog(@"Checking: running OS is equal to %@, checking build version", expectedVersion);
  if (!expectedBuilds.count) {
    NSLog(@"Exiting: No preferred build, so considered equal");
    [NSApp terminate:nil];
  }
  if ([expectedBuilds containsObject:systemBuild]) {
    NSLog(@"Exiting: OS build is one of the expected builds %@", expectedBuilds);
    [NSApp terminate:nil];
  }
  NSLog(@"Checking: OS build not found in expected builds %@", expectedBuilds);
} else if ([systemVersionArray[0] intValue] < [expectedVersionArray[0] intValue] ||
           [systemVersionArray[1] intValue] < [expectedVersionArray[1] intValue] ||
           [systemVersionArray[2] intValue] < [expectedVersionArray[2] intValue]) {
  NSLog(@"Checking: OS build is lower than required");
} else {
  NSLog(@"Exiting: OS build is greater than required");
  [NSapp terminate:nil];
}

[russellhancox]

Use expectedBuilds.count == 0 or !expectedBuilds.count to catch both nil and an empty array

[russellhancox]

As the last line of the first condition exits, there's no need for the else, might as well remove it and reduce the indentation.

[tburgin]

nit: For large expectedBuilds builds list, a set theoretically has faster lookups.

NSString *buildsKey = @"expectedBuilds";
NSString *builds = NSLocalizedString(buildsKey, @"");
NSSet *expectedBuilds = [NSSet setWithArray:[builds componentsSeparatedByString:@","]];
if (!expectedBuilds.count || [expectedBuilds containsObject:buildsKey]) expectedBuilds = nil;