Show better warning when dependency recipe is overridden

[raxod502]

We currently have a warning

Two different recipes given for org-noter (:flavor cannot be both melpa and nil)

which is produced when a recipe conflict happens, see #518. However this is not very informative to the end user in the most common case, which is that the package was pulled in as a dependency unbeknownst to them, using the default recipe, and then they try to specify a custom recipe for it. We have the data available to detect when this has happened, so we should use it and display a different warning, like

Custom recipe given for org-noter, but it was already pulled in as a dependency using the default recipe

[matthuszagh]

Is it possible to also specify the package that pulled in the dependency? This would make it easier to rearrange an init file so that the custom recipe is evaluated first.

[raxod502]

Yep, sounds like a good idea and simple to implement (the data already exists at the right place as it is used when displaying messages about build system status).

[blak3mill3r]

As things stand today, is there any good way to inspect the tree of transitive dependencies? I have no idea which of my packages is pulling in cider via the default recipe.

The only way I know to find it is commenting out packages, which is tedious.

[raxod502]

We don't have anything graphical at the moment, but all the needed information is available in the straight--build-cache variable. For example, in mine there's an entry for

               "cider"
               ("2021-05-02 05:30:15"
                ("emacs" "clojure-mode" "parseedn" "pkg-info" "queue" "spinner" "seq" "sesman")
                (:type git :flavor melpa :files
                       ("*.el"
                        (:exclude ".dir-locals.el")
                        "cider-pkg.el")
                       :host github :repo "clojure-emacs/cider" :package "cider" :local-repo "cider"))

which indicates that the cider package has dependencies on all of ("emacs" "clojure-mode" "parseedn" "pkg-info" "queue" "spinner" "seq" "sesman"). In my installation, since cider doesn't appear anywhere else, I know nothing else depends on it. Presumably, in your installation, you'd find a different result.

[jasonhemann]

This variable might be worth mentioning in the README file. I had a hard time finding it.

[progfolio]

@jasonhemann the straight-dependents command is available for this now.

[raxod502]

Right, we want to avoid documenting such internal variables, and instead we want to provide user-facing commands that have a stable and well-designed API, like the one @progfolio mentioned.

[jasonhemann]

Even better