cfe44351

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

Skip a build directory by its whole name, not by a prefix of it

The discovery walk skipped any directory whose name started with "result",
meaning to skip a nix build output. It also skipped one called "results", and
every package under it went missing from discovery with nothing reported: a
walk that finds no cabal file and a walk that refused to look are the same
answer to a caller.

The two build directories it still skips are compared as whole names now, and
so is anything hidden. "result" is not named at all: it is a symlink to a build
output, which the walk follows like any other directory and which holds no cabal
file to find. Refusing to follow a symlink would have been the same silent loss
in a different guise, because a repository that links a package in has one to
find there.

The predicate is top-level and exported, where the walk had it in a where clause
with no signature and no test. It is pure, so the prefix case is a unit test
rather than a walk over a fixture, and there is a fixture too: a package two
levels under a directory called results, which is what was being dropped.

The fixture needed a line in .gitignore. The global ignore file has result*,
which hides a directory called results the same way this walk did.

Timeline