refactor: integrate callback into motifs() function

[Copilot]

Integrates callback functionality into motifs() as an optional parameter instead of exporting a separate function. Aligns API with cluster_leading_eigen() pattern.

Changes

• motifs() function: Added optional callback parameter

  • Returns motif counts when callback = NULL (existing behavior)
  • Calls motifs_randesu_callback_closure_impl() and returns NULL invisibly when callback provided

• motifs_randesu_callback() function: Removed entirely (not exported)

• Tests: Updated to use motifs(callback = ...) syntax

• Documentation:

  • Added callback parameter docs and example showing early search termination
  • Changed "3-6" to "3 to 6"
  • Removed redundant 1-based indexing clarification

Example

g <- sample_pa(100)

# Count all motifs (existing behavior)
motifs(g, 3)

# Stop search after finding 5 motifs (new)
count <- 0
motifs(g, 3, callback = function(vids, isoclass) {
  count <<- count + 1
  count < 5
})

• By submitting this pull request, I assign the copyright of my contribution to The igraph development team.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Refine callback implementation</issue_title>
<issue_description>Address post-merge feedback in #2465 . Specifically, integrate the new _impl into the top-level motifs() function instead of exporting a new function.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Refine callback implementation #2543

---

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[krlmlr]

Drop the function entirely, not needed.

[Copilot]

Done in 1130037. The motifs_randesu_callback() function has been removed entirely. The callback functionality is now only available through the motifs(callback = ...) parameter.

[Copilot]

Pull request overview

This PR refactors the motif search callback functionality by integrating it as an optional parameter into the existing motifs() function, following the pattern established by cluster_leading_eigen(). This simplifies the API by removing the need for a separate exported function.

Changes:

• Integrated callback functionality into motifs() as an optional parameter, maintaining backward compatibility
• Removed motifs_randesu_callback() function (no longer exported)
• Updated all tests and documentation to use the new motifs(callback = ...) syntax

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
R/motifs.R	Added callback parameter to motifs() function; removed standalone motifs_randesu_callback() function; fixed error message formatting
tests/testthat/test-motifs.R	Updated all callback tests to use new motifs(callback = ...) API
tests/testthat/_snaps/motifs.md	Updated snapshot test header to reflect new API naming
man/motifs.Rd	Added callback parameter documentation and example; improved text clarity ("3 to 6" instead of "3-6")
man/motifs_randesu_callback.Rd	Removed documentation file for deleted function
man/sample_motifs.Rd	Removed reference to deleted motifs_randesu_callback() function
man/graph.motifs.Rd	Updated text clarity ("3 to 6" instead of "3-6")
man/dyad_census.Rd	Removed reference to deleted motifs_randesu_callback() function
man/count_motifs.Rd	Removed reference to deleted motifs_randesu_callback() function
NAMESPACE	Removed export of motifs_randesu_callback()
.gitignore	Minor formatting fix (added leading slash for consistency)