audit: fix "version should not decrease" check.

[MikeMcQuaid]

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---

Fix the "version should not decrease" check so it correctly handlesversion_schemes.

CC @ilovezfs @zmwangx

Fixes #1489.

[ilovezfs]

Library/Homebrew/formula_versions.rb:78:11: C: Use next to skip iteration.

[ilovezfs]

Crash bug with dbus:

iMac-TMP:~ joe$ brew audit dbus
dbus:
  * version should not decrease
Error: 1 problem in 1 formula
iMac-TMP:~ joe$ brew pull https://github.com/Homebrew/brew/pull/1493
==> Fetching patch 
Patch: https://github.com/Homebrew/brew/pull/1493.patch
==> Applying patch
Applying: audit: fix "version should not decrease" check.
==> Patch closes issue #1493
==> Patch changed:
 Library/Homebrew/dev-cmd/audit.rb    | 37 ++++++++++++++++++++++++------------
 Library/Homebrew/formula_versions.rb | 16 +++++++++++++---
 2 files changed, 38 insertions(+), 15 deletions(-)
iMac-TMP:~ joe$ brew audit dbus
Error: undefined method `empty?' for nil:NilClass
Please report this bug:
  https://git.io/brew-troubleshooting
/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:675:in `block (2 levels) in audit_revision_and_version_scheme'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:670:in `each'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:670:in `block in audit_revision_and_version_scheme'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:669:in `each'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:669:in `audit_revision_and_version_scheme'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:1065:in `audit'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:72:in `block in audit'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:68:in `each'
/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:68:in `audit'
/usr/local/Homebrew/Library/Homebrew/brew.rb:94:in `<main>'

[MikeMcQuaid]

Fixed those issues but dbus will still fail because we've got a version number decrease without a version_scheme bump. Need to think how best to address that but probably worth merging this as-is for now as it's not any worse.

[ilovezfs]

Maybe not worse, but it did change the output

iMac-TMP:Homebrew joe$ brew audit dbus
dbus:
  * stable version should not decrease
Error: 1 problem in 1 formula

[MikeMcQuaid]

Yeh, it adds "stable" on to be clear which spec it's referring to. I think that's probably better in figuring out what's happened.

[ilovezfs]

Should this really close #1489 if the dbus problem is still unfixed?

[ilovezfs]

any way to avoid the repetitiveness of 671-672 and 674-675?

[MikeMcQuaid]

Not really, nope.

[ilovezfs]

can attributes_map[:revision] be nil?

[MikeMcQuaid]

No.

[MikeMcQuaid]

Should this really close #1489 if the dbus problem is still unfixed?

Yes because the issue described in the title/body has been addressed: this is now considering version_scheme. It's a different problem to figure out how we do this with "latest" vs. "compare the last 10 formula changes".

[MikeMcQuaid]

Arguably we should consider bumping version_scheme whenever we accidentally pull a too-new version and revert back to a stable one. The audit check is correct in this case, it's just not how we want it to behave.

[MikeMcQuaid]

To be clear though: I'm definitely 👍 on having a new issue describing how we do want this to behave in the dbus case.

[ilovezfs]

Since version_scheme didn't exist then, and the too new one was rolled back minutes later, it seems goofy to have to slap a version scheme on it at this point, and an abuse of what that DSL was for.