extract: use downcased version in filename

[scpeters]

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Formula filenames are required to be lowercase, so the brew extract command should downcase the version before using it to construct the filename. I noticed this while performing brew extract tbb@2020, which has version 2020_U3 and resulted in a formula with filename tbb@2020_U3.rb

[BrewTestBot]

Review period will end on 2021-05-27 at 06:33:02 UTC.

[scpeters]

I suppose that we may also want to add a diagnostic to complain about capital letters in formula filenames, since it took me a little while to figure out what the problem was that led to this fix

[Bo98]

it took me a little while to figure out what the problem was that led to this fix

What were you seeing when it had an uppercase character? An error?

[scpeters]

it took me a little while to figure out what the problem was that led to this fix

What were you seeing when it had an uppercase character? An error?

I was trying to build bottles for tbb@2020_U3 and a dependent in the same pull request (osrf/homebrew-simulation#1483). The tbb@2020_U3 bottle built fine, but when installing dependencies for the dependent formula, it was trying to fetch the bottle that it had just built, even though it was still installed:

• https://build.osrfoundation.org/job/generic-release-homebrew_triggered_bottle_builder/462/label=osx_catalina/console

==> Running Formulae#formula!(osrf/simulation/gazebo11)
==> Determining dependencies...
==> brew fetch --retry ampl-mp aom ... tbb tbb@2020_U3 ... zimg
==> FAILED
...
==> Fetching tbb@2020_U3 from osrf/simulation
==> Downloading https://osrf-distributions.s3.amazonaws.com/bottles-simulation/tbb%402020_U3-2020_U3.catalina.bottle.tar.gz
curl: (22) The requested URL returned error: 404 Not Found
==> Retrying download
==> Downloading https://osrf-distributions.s3.amazonaws.com/bottles-simulation/tbb%402020_U3-2020_U3.catalina.bottle.tar.gz
curl: (22) The requested URL returned error: 404 Not Found
Error: Failed to download resource "tbb@2020_U3"
Download failed: https://osrf-distributions.s3.amazonaws.com/bottles-simulation/tbb%402020_U3-2020_U3.catalina.bottle.tar.gz

I couldn't pinpoint the exact problem, but it may be related to a downcase call in formulary.rb. I also noticed in the formula cookbook that "Filenames should be all lowercase".

[BrewTestBot]

Review period ended.

[Bo98]

Hmm yeah it should probably handled a bit better. This fix is correct to make anyway.

[scpeters]

I suppose that we may also want to add a diagnostic to complain about capital letters in formula filenames

#11447

[MikeMcQuaid]

Nice work here @scpeters!