Checks a cookbook, or your local recipes, for mix composer.cookbook.lint.

Lint is a set of plain functions: it takes discovered cookbooks, prints nothing and never raises. Every problem is a Composer.Lint.Diagnostic, located where it is written (see Composer.Error.anchor/1 and Composer.Recipe.Locator), in a stable order. Recipes are checked in two passes: each entry of each recipe on its own (so every bad reference is reported), then each recipe as a whole (for cycles and conflicting installs); a problem is reported once, in the recipe that has it.

Errors, for a package cookbook (run/3):

• every step has a summary, an action and a stability
• every step has a test at test/composer/<cookbook>/steps/<id>_test.exs
• every step reference in requires resolves
• the committed manifest holds the same data as a freshly built one
• the recipe group rules below
• every recipe resolves (with every include followed); this also reports a cookbook alias named like an installed cookbook
• a leftover cookbook-level templates/ directory
• a file under steps/ that no step owns: it is not in a step's template directory (steps/_<id>/, beside steps/<id>.ex)
• a step's templates in an unprefixed steps/<id>/ directory
• a .ex file under steps/ that is not a compiled step module
• a template/1 path that does not exist

Files under steps/ that git ignores are skipped.

Errors, for local (local/2):

• a steps/ or templates/ directory (local holds recipes only)
• any other entry besides recipes/ that composer does not recognize
• the recipe group rules below
• every recipe resolves

Recipe group rules:

• a subdirectory under recipes/ (groups are files)
• a group file with an invalid name
• a group file that is not a keyword list of recipes
• a duplicate recipe name within a group
• a recipe missing shortdoc or steps, with an unknown key, or with a value of the wrong type; a shortdoc on more than one line
• an if: flag that the recipe does not declare in its own flags
• an invalid, reserved (core, hex, local), duplicate or atom-valued cookbook alias, or one whose target is not a package cookbook name
• a recipe named like a group of the same cookbook

Warnings:

• an empty group
• a cookbook alias that none of the recipe's own references use
• an alias that names different cookbooks in two recipes of one group
• a step and a recipe share an id, which is allowed but confusing
• a file in a step's template directory that its template/1 calls never refer to (skipped for a step whose template/1 path is computed at run time)

A file belongs to the step named by the first directory on its path that starts with _: steps/ash/_postgres/x/y belongs to ash/postgres. Step path segments never start with _, so a steps/<id>/ directory only ever holds child steps.