format-shell-command

I liked this script that @bbkane had posted on Reddit, especially in conjunction with the suggestion to make it into a nvim command.

I forked it to make a minor style change: unix pipes | can actually function as line continuations. Instead of

echo foo \
    | awk '{ print $1}'

I much prefer

echo foo |
    awk '{ print $1}'

Anyway, I think that responsiveness is pretty important when writing code, and the experience with this kind of code formatting may really benefit from shaving off a few milliseconds. It seemed like a good excuse for me to keep practicing my rust, even more so since much of the python code looked like it was begging to be made into an enum or a match, and I thought that the python generator (something I really miss in rust) would probaby be not terribly difficult to rewrite as an iterator.

My very naive rewrite took a few hours -- possibly longer than it would have taken me to write the python from scratch -- but its relative performance is nothing to shrug off.

I strongly suspect that opportunities for further optimizations (e.g. decreasing String allocations, implement FromStr to parse Expr, get rid of panic / proper error handling, implement the tests) would be obvious for a better rust programmer, but that's part of the point -- this was simply the most obvious way that I could get the code to compile, and it is 30 times faster.

$ hyperfine --warmup=5 $'echo "echo -n \'hi there\' | awk \'{ print $1 }\' | sed -n \'s/i/aha/p\'" | ~/gists/9acab6b3bd1478343296d
9fd02e08bc4/format_shell_cmd.py'
Benchmark #1: echo "echo -n 'hi there' | awk '{ print $1 }' | sed -n 's/i/aha/p'" | ~/gists/9acab6b3bd1478343296d9fd02e08bc4/format_shell_cmd.py
  Time (mean ± σ):     163.3 ms ±   7.4 ms    [User: 71.7 ms, System: 65.8 ms]
  Range (min … max):   153.8 ms … 182.2 ms    18 runs
 
$ hyperfine --warmup=5 $'echo "echo -n \'hi there\' | awk \'{ print $1 }\' | sed -n \'s/i/aha/p\'" | target/release/format-shell-command'
Benchmark #1: echo "echo -n 'hi there' | awk '{ print $1 }' | sed -n 's/i/aha/p'" | target/release/format-shell-command  
  Time (mean ± σ):       4.8 ms ±   3.8 ms    [User: 1.6 ms, System: 2.2 ms]
  Range (min … max):     1.6 ms …  24.4 ms    145 runs
 
  Warning: Command took less than 5 ms to complete. Results might be inaccurate.
  Warning: Statistical outliers were detected. Consider re-running this benchmark on a quiet PC without any interferences from other programs. It might help to use the '--warmup' 
or '--prepare' options.