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Checking existence of files with both title.exists and title.file.exists increments the expensive function count by two
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With gerrit 178698, Scribunto's mw.title objects no longer increment the expensive parser function count upon creation, instead incrementing it when "expensive" properties such as title.exists are accessed.

While playing around with this new functionality, I found that for files, existence checks using title.exists and title.file.exists increment the expensive function count separately.

For example:

local title = 'File:Example.png' )
local temp = title.exists
temp = title.file.exists

This code will increment the expensive function count by two, even though it's checking essentially the same thing. The same goes for checking the other way around:

local title = 'File:Example.png' )
local temp = title.file.exists
temp = title.exists

That's also +2 to the expensive function count.

Ideally, both of these examples would only add one to the expensive function count, although I can't see this problem actually affecting modules in practice, as I can't imagine a reason for using both title.exists and title.file.exists on the same file.

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MrStradivarius assigned this task to Jackmcbarn.
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I agree we can probably make the second example cheap, but not the first one. Remember that a file description page can exist without a file existing.

Good point - I was forgetting that. It looks like the documentation needs to be changed then. At the moment it says that title.exists is an alias for title.file.exists, but the two return different results if the file description exists but the file doesn't.

Ah, the docs say the Media namespace, not the file namespace, so actually they were correct. I'll edit them a bit to make the distinction between Media namespace titles and File namespace titles clearer.

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