Gulp docs say it's a string: https://github.com/gulpjs/gulp/blob/4.0/docs/API.md#gulplastruntaskname-timeresolution

Undertaker docs say it's either a string or a function: https://www.npmjs.com/package/undertaker#lastruntask-timeresolution

Is this patch as a result of something breaking or from reading docs?

(I actually prefer the function syntax. Just wondering)

It was failing when I used a string - maybe that's a bug.

The error is AssertionError: Only functions can check lastRun when passing a string.

I believe it tries to look up the task function by string and checks last-run of the function. That assertion might be due to a failed lookup of the string. I'm on mobile currently and can't dig into the code.

Just tested the example and it works. However, because it is a snippet, it doesn't portray that the images function needs to be registered as a task with gulp.task(images). When it isn't registered as a task, I get a thrown error but it isn't the same as the one @jakearchibald encountered.

@jakearchibald would you like to change this PR to include the task registration portion? I think that would make more sense to new users.

I don't have strong feelings, but gulp.lastRun(fn) feels easier to understand than gulp.lastRun(string).

With since: gulp.lastRun(images) I read "Since the last run of the images function".

With since: gulp.lastRun("images") I wasn't sure. I figured that the string might just be an ID, so it'd be "Since the last call of gulp.lastRun("images")", but then that didn't work. If I also saw gulp.task(images) I'd be similarly confused, as I'd need to know that somewhere behind the scenes it was getting the name of the function images and storing it.

I'm fine with that change too.

If you're happy with lastRun(fn), then this PR is good to go, unless I'm missing something.

Thanks! 😃

@jakearchibald would you like to change this PR to include the task registration portion? I think that would make more sense to new users.

I guess that's why it wasn't merged! May have merged this prematurely - my mistake. 😳

I'll add the task registration to the README now.

The task registration portion isn't needed if you're providing a function to lastRun.

Right, makes sense now. Whoops!