Bash and CDPATH

Fun fact, having CDPATH exported will cause it to also emit any fuzzy matched to stdout.

I spent entirely too long digging into a Makefile where it had something clever like:

    $(eval HAS_DELTA := $(shell cd src && gofmt -l $(PKGS))
    if [[ -n "$HAS_DELTA" ]]; then echo "reformat your code please:\n$HAS_DELTA"; exit 1; fi 

Turns out that the path src didn't exist, but because I had mistakenly exported a CDPATH variable in my .bashrc (which has since been corrected):

export CDPATH="some/path:another/path/with/a/src/sub-directory"

There was a matching sub directory path that Make's $(shell cd src && ...) matched and emitted which made that clever if [[ -n "$HAS_DELTA" ]] really upset. When it failed, the message printed was the fuzzy-matched path itself.. which wasn't helpful in trying to diagnose things.

How did I diagnose this? Tracing!

# Turn on shell tracing to see where the output is printed:
SHELL = /usr/bin/bash -x

    # ...