NightOwl888 edited a comment on issue #308:
URL: https://github.com/apache/lucenenet/issues/308#issuecomment-666186961
> Debug.Assert(!SlowFileExists(directory, newFileName), "file \"" +
newFileName + "\" already exists; siFiles=" +
string.Format(J2N.Text.StringFormatter.InvariantCulture, "{0}", siFiles)); ...
Since this only runs in Debug builds, i wonder if the unit tests on the build
server are running in debug mode? This assertion actually comes with a lot of
overhead!! It also takes a lock on the same lock that we are waiting on within
MockDirectoryWrapper.locker.
This goes to the heart of one of a few dozen issues that I have written down
in a notebook that I haven't reported on GitHub yet.
In Java, it is possible to turn on and off asserts in a production build,
they aren't simply compiled out of the build. They are turned on during
testing. What this effectively means is that there are a whole suite of tests
(namely anything that is using `System.Diagnostics.Debug.Assert()` currently)
that we are completely skipping. To make matters even more complicated, some
parts of the test framework are designed to catch the `AssertionError` that is
thrown from those asserts when they fail and ignore them, and other parts are
designed to fail the test in those cases.
I recently "fixed" a related issue (#299) by throwing
`InvalidOperationException`, but I see that may have been the wrong approach,
since the test framework has different behavior for `AssertionException` and
`InvalidOperationException` in some cases.
I have been considering ways of reproducing the Java assertion behavior
without producing negative performance impacts in production. But one of the
main things to note is that `Debug.Assert()` is implemented as a regular
function in .NET, meaning that both parameters are resolved first before it is
called. Putting an expensive function call and/or expensive string building
operation there is what is causing this problem in Debug builds. In Java, the
asserts are not implemented as a function, and I suspect the compiler doesn't
run the string building operation unless the assert fails, and I am sure
neither of them are run if assertions are disabled.
What is needed is to come up with a solution that allows us to turn on
asserts during testing in a way that doesn't hamper debug or runtime
performance. One option I have been considering is to create a wrapper for
`Debug.Assert`, something like:
```c#
internal static class Debugging
{
public static bool AssertsEnabled { get; set; } =
SystemProperties.GetPropertyAsBoolean("assert", false);
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static void Assert(Func<bool> conditionFactory, Func<string>
messageFactory)
{
if (AssertsEnabled)
{
if (!conditionFactory())
throw new AssertionException(messageFactory());
}
else
{
Debug.Assert(conditionFactory(), messageFactory()); // Note this
line is completely removed from Release builds
}
}
}
```
Which can be used like:
```c#
Debugging.Assert(() => !SlowFileExists(directory, newFileName), () => "file
\"" + newFileName + "\" already exists; siFiles=" +
string.Format(J2N.Text.StringFormatter.InvariantCulture, "{0}", siFiles));
```
I suspect to get optimal production performance, we will probably also have
to duplicate the `AssertsEnabled` check, even though it is not DRY. That will
completely cut off the execution path to the fallback `Debug.Assert()` call in
debug mode, but being that it is implemented as a function, it is probably best
that we don't include it for debugging anyway and just rely on turning
assertions "on" or "off".
```c#
if (Debugging.AssertsEnabled)
Debugging.Assert(() => !SlowFileExists(directory, newFileName), () =>
"file \"" + newFileName + "\" already exists; siFiles=" +
string.Format(J2N.Text.StringFormatter.InvariantCulture, "{0}", siFiles));
```
Do note that the `AssertionException` already exists in the test framework.
I have been trying to avoid putting testing code in the release, but it appears
in order to duplicate this behavior we will either need to or come up with a
solution that involves injecting a class for testing purposes or include it in
the release code. Certainly to turn "on" and "off" asserts in production, it
would be easier to follow the former approach.
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