brew alias automatically re-symlinks missing aliases

[kabel]

Allows aliases saved from a backup of BASE_DIR to be rewritten and symlinked into Homebrew install.

[MikeMcQuaid]

Nice work, thanks for the PR! Wondering if it might be worth doing this automatically on all/any other commands instead/as well? Could you try to benchmark with hyperfine?

[kabel]

Thanks. It might be useful to just bake this in automatically to the standard brew alias listing command, but that would seem to add side-effects to an otherwise read-only operation. Having an explicit command to re-write the alias file and symlink seems the most appropriate for users to invoke as desired to fix an alias that exists but doesn't execute (missing symlink in path).

I haven't done any benchmark with hyperfine before, but it seems pretty straightforward. The command will likely scale with the number of file-defined aliases. The slowest part of my script was just setting up 50 test aliases, which is slower than you'd expect.

#!/bin/bash

# setup test aliases, removing bin
for i in {1..50}
do
    NAME="test$i"
    brew alias "$NAME=info"
    rm -f "$HOMEBREW_PREFIX/bin/brew-$NAME"
done

# measure repair
hyperfine "brew alias --repair"

function finish {
    # cleanup
    for i in {1..50}
    do
        NAME="test$i"
        brew unalias "$NAME"
    done
}

trap finish EXIT

Results are pretty typical:

Benchmark 1: brew alias --repair
  Time (mean ± σ):      1.212 s ±  0.020 s    [User: 0.572 s, System: 0.365 s]
  Range (min … max):    1.186 s …  1.252 s    10 runs

[MikeMcQuaid]

Thanks. It might be useful to just bake this in automatically to the standard brew alias listing command, but that would seem to add side-effects to an otherwise read-only operation.

Would that operation not fail (or at least fail to produce the expected output) without running --repair?

[kabel]

Would that operation not fail (or at least fail to produce the expected output) without running --repair?

Not exactly, which is the confusing part. brew alias will still be able to read and list the file that have been saved in the $HOME/.brew-aliases. However, invoking those commands will not work until --repair puts them back into $HOMEBREW_PREFIX/bin with the appropriate brew- bin prefix.

Example problem:

% brew alias test1=info
% rm -f $HOMEBREW_PREFIX/bin/brew-test1
% brew alias
brew alias test1='info'
% brew test1
Error: Unknown command: test1
% brew alias --repair
% brew test1
255 kegs, 132,498 files, 4.2GB

[MikeMcQuaid]

However, invoking those commands will not work until --repair puts them back into $HOMEBREW_PREFIX/bin with the appropriate brew- bin prefix.

I feel like brew alias commands would ideally just do the repair automatically given how relatively fast it is. This feels more useful to users rather than learning another flag. Thoughts?

[MikeMcQuaid]

Yeh, this makes a lot more sense to me, thanks @kabel!