Warn about missing libraries in brew info

[HaraldNordgren]

This bit me when on an old version of ffmpeg, after upgrading it it started working. So I can't reproduce the exact issue.

But manually breaking a library to show what it looks like: mv /Users/Harald/git-repos/github.com/Homebrew/brew/Cellar/gmp/6.3.0/lib/libgmp.10.dylib{,.bak}

❯ ./bin/brew info gmp shellcheck
==> gmp ⚠: stable 6.3.0 (bottled), HEAD
GNU multiple precision arithmetic library
https://gmplib.org/
Installed (as dependency)
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/g/gmp.rb
License: LGPL-3.0-or-later OR GPL-2.0-or-later
==> Installed Kegs and Versions
gmp ✔ 6.3.0 (22 files, 3.4MB)
==> Dependencies
Missing libraries (1): libgmp.10.dylib ✘

==> shellcheck ✔: stable 0.11.0 (bottled), HEAD
Static analysis and lint tool, for (ba)sh scripts
https://www.shellcheck.net/
Installed (on request)
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/s/shellcheck.rb
License: GPL-3.0-or-later
==> Installed Kegs and Versions
shellcheck ✔ 0.11.0 (8 files, 68.4MB)
==> Dependencies
Required (1): gmp ⚠
Recursive Runtime (1): all installed ✔
Dependents: 1

---

• Have you followed our Contributing guidelines?
• Have you checked for other open Pull Requests for the same change?
• Have you explained what your changes do? Performance claims (e.g. "this is faster") must include Hyperfine benchmarks.
• Have you explained why you'd like these changes included, not just what they do?
• For bug fixes, have you given step-by-step brew commands to reproduce the bug?
• Have you written new tests (excluding integration tests)? Here's an example.
• Have you successfully run brew lgtm (style, typechecking and tests) locally?

---

• AI was used to generate or assist with generating this PR.

Claud Code wrote the code with my guidance.

---

[github-actions]

Thanks for your pull request. This has been closed because it appears to use an incomplete or outdated pull request template.

Please edit this pull request to fill in the current pull request template. This workflow will reopen this pull request automatically once the template is complete. Do not open a new pull request for this.

[HaraldNordgren]

Benchmarks:

❯ hyperfine --warmup 3 --runs 15 \
  -L cache cold,warm \
  -L term 'gmp shellcheck' \
  -L sha 'main,info-missing-libraries-warning' \
  --prepare '
    mv /Users/Harald/git-repos/github.com/Homebrew/brew/Cellar/gmp/6.3.0/lib/libgmp.10.dylib{,.bak}
    set -e
    git checkout {sha}
    if [ "{cache}" = "cold" ]; then
      rm -f ~/Library/Caches/Homebrew/linkage.json
    fi
  ' \
  "./bin/brew info {term}"
Benchmark 1: ./bin/brew info gmp shellcheck (cache = cold, sha = main)
  Time (mean ± σ):     644.1 ms ±  10.9 ms    [User: 406.3 ms, System: 100.7 ms]
  Range (min … max):   627.9 ms … 664.3 ms    15 runs

Benchmark 2: ./bin/brew info gmp shellcheck (cache = warm, sha = main)
  Time (mean ± σ):     640.8 ms ±   8.7 ms    [User: 407.1 ms, System: 98.1 ms]
  Range (min … max):   629.1 ms … 652.0 ms    15 runs

Benchmark 3: ./bin/brew info gmp shellcheck (cache = cold, sha = info-missing-libraries-warning)
  Time (mean ± σ):     674.2 ms ±   8.1 ms    [User: 422.9 ms, System: 113.8 ms]
  Range (min … max):   658.3 ms … 683.5 ms    15 runs

Benchmark 4: ./bin/brew info gmp shellcheck (cache = warm, sha = info-missing-libraries-warning)
  Time (mean ± σ):     645.1 ms ±   7.4 ms    [User: 409.5 ms, System: 98.5 ms]
  Range (min … max):   635.5 ms … 655.8 ms    15 runs

Summary
  ./bin/brew info gmp shellcheck (cache = warm, sha = main) ran
    1.01 ± 0.02 times faster than ./bin/brew info gmp shellcheck (cache = cold, sha = main)
    1.01 ± 0.02 times faster than ./bin/brew info gmp shellcheck (cache = warm, sha = info-missing-libraries-warning)
    1.05 ± 0.02 times faster than ./bin/brew info gmp shellcheck (cache = cold, sha = info-missing-libraries-warning)

[MikeMcQuaid]

Thanks! Can you benchmark this on big formulae/those with lots of linkage e.g. ffmpeg-full, llvm, boost?

[MikeMcQuaid]

Avoid ternary here, I think it makes it harder to read. Would prefer ||= on both variables.