Implicit order of choosing parameter names changed in 6.x, but still inconsistent with documentation

[amiryal]

From the documentation:

If all names for a parameter contain dashes, the internal name is generated automatically by taking the longest argument and converting all dashes to underscores.

However, in the implementation, when the possible names are sorted, it’s only for the purpose of grouping them “long options first” — meaning “options with two dashes first”, not “longest name first”.

See current master:

click/click/core.py

Line 1641 in 2e856a5

possible_names.sort(key=lambda x: -len(x[0])) # group long options first

And compare with branch 5.x:

click/click/core.py

Line 1506 in 7ede2db

possible_names.sort(key=lambda x: len(x[0]))

Between version 5.x and 6.x, the implicit (misdocumented) order had changed, which broke my script.

This bug manifests only when multiple long parameter (option) names are specified, i.e.:

@click.option('--shorter', '--longer-option')

…in which case different versions of Click would choose a different name between shorter and longer_option instead of always choosing longer_option as suggested in the documentation.

[davidism]

Duplicate of #1140