| commit | d54e85569d47be6e6406055190a66430b6a905b7 | [log] [tgz] |
|---|---|---|
| author | Joe Tsai <joetsai@digital-static.net> | Tue Jul 25 13:30:04 2017 -0700 |
| committer | GitHub <noreply@github.com> | Tue Jul 25 13:30:04 2017 -0700 |
| tree | 913c812409efa1d92f133560f2fb5bf6b7499492 | |
| parent | b8dbfba87748393ea3632df42dcc82302adf5cdf [diff] |
Expand dynamic checks of options (#20) Add checks for mutations of the input value and non-deterministic transformer outputs. A prior approach (not shown in this commit) attempted to detect mutations of the input by hashing the inputs before and after calling the option functions. However, we deemed this approach too restrictive since there are legitimate cases where some types lazily update their values upon first access (for example, accessing extensions on proto2 messages). This would cause the hashes to mismatch and provide a false-positive panic. In this approach, we accept the reality that lazy evaluators exist, but make the assumption that any lazy evaluators are protected by a mutex of some sort. Thus, we simply run the option function twice in parallel, and let the race detector detect mutations on the input. We intentionally run the options in a function named detectRaces to make it obvious from the stack trace what's going wrong. For the detection of deterministic output of Transformers, we call a special version of s.compareAny so that the outputs may be compared according to the semantics of what the user provided. The specialized wrapper s.statelessCompare preserves the comparison state such as the current result and the reporter.
This package is intended to be a more powerful and safer alternative to reflect.DeepEqual for comparing whether two values are semantically equal.
The primary features of cmp are:
When the default behavior of equality does not suit the needs of the test, custom equality functions can override the equality operation. For example, an equality function may report floats as equal so long as they are within some tolerance of each other.
Types that have an Equal method may use that method to determine equality. This allows package authors to determine the equality operation for the types that they define.
If no custom equality functions are used and no Equal method is defined, equality is determined by recursively comparing the primitive kinds on both values, much like reflect.DeepEqual. Unlike reflect.DeepEqual, unexported fields are not compared; they result in panics unless suppressed by using an Ignore option.
This is not an official Google product.
go get -u github.com/google/go-cmp/cmp
BSD - See LICENSE file