Improve legacy package migration from mod_exeweb and mod_exescorm

[erseco]

Summary

mod_exelearning ships a non-destructive, site-wide tool that migrates legacy mod_exeweb and mod_exescorm activities into new eXeLearning activities (admin/migrate.php, classes/local/migration/*). The detection that decided what was migratable was fragile and inconsistent between the two source handlers:

• exescorm_source only treated a package as migratable when its filename ended in .elpx or the SCORM zip embedded an .elpx. A package that is itself a content.xml-bearing .zip (an eXeLearning content export / IMS export stored under a non-.elpx name) was reported nosource and silently skipped.
• exeweb_source never inspected the package contents — it returned ok whenever any file existed in the package filearea, so a package with no recoverable eXeLearning source either failed at extraction (STATUS_ERROR) or migrated as a sourceless shell.

The migratability rule is now explicit and content-based: a package is migrated only when an eXeLearning content.xml (ODE 2.0) source can be recovered from it.

Package types now covered

Package	Marker	Result
Native .elpx	content.xml at root	migrated (direct) — unchanged
eXeLearning content .zip / IMS export / web export bundling source	content.xml at root	migrated (direct) — newly recovered
eXeLearning SCORM export wrapping its source	exactly one embedded .elpx	migrated (embedded) — unchanged
Several embedded .elpx	>1 .elpx	skipped ambiguoussource
Legacy .elp	contentv3.xml, no content.xml	skipped nosource
Source-less SCORM / plain web export	no content.xml, no .elpx	skipped nosource
External / AICC URL / synced (exescorm)	exescormtype	skipped unsupported
Corrupt / unreadable archive	—	skipped nosource (no exception)

Skipped packages lose no data: the migration never deletes the source, so the legacy activity stays intact and is reported in the preflight/result table.

Changes

• New classes/local/migration/source/package_probe.php — a shared, content-based classifier/resolver used by both source handlers. It reads only the ZIP central directory (preflight-cheap), decides the verdict from a root content.xml (precedence) or a single safe embedded .elpx, and resolves the package to a temp path (whole archive for a direct package; only the embedded entry otherwise). It reuses the existing zip_utils path-traversal/symlink defences.
• exescorm_source and exeweb_source now delegate detection and resolution to package_probe. exescorm_source keeps its external/aiccurl/localsync → unsupported short-circuit; exeweb_source keeps its revision-itemid resolution with the restored-backup fallback scan.
• lang/en/exelearning.php — migratescormnote and migratestatus_nosource now state the content.xml criterion and that legacy .elp / source-less SCORM / web exports are skipped. The existing nosource bucket is reused (no new statuses or table columns).
• The extraction engine (package_manager::extract_stored), migration_service, grade sync, view.php and the DB schema are unchanged — the change is confined to source detection.

mod_exeweb vs mod_exescorm differences

• mod_exeweb stores one package in the package filearea at itemid = {exeweb}.revision and wipes the area on each save; it has no grades, so the target uses the per-iDevice grade model and no grade migration runs. Detection had to inspect contents (it previously did not).
• mod_exescorm stores its package at itemid 0, supports several exescormtypes (local, localsync, embedded = a raw .elpx, external, aiccurl), and carries grades that are copied to the target's overall grade item. External/AICC-URL and synchronized types keep no migratable static snapshot and stay unsupported. The gap was a genuine SCORM/content .zip with no embedded .elpx.

Both now share one detector, so the rule lives in exactly one place.

Testing performed

• New tests/local/migration/package_probe_test.php covers every branch (native .elpx, content.xml zip, single/multiple embedded .elpx, source-less SCORM, legacy .elp, corrupt archive, itemid threading, blocked-verdict and unsafe-entry resolution).
• Extended exescorm_source_test, exeweb_source_test and migration_service_test (end-to-end install of a content.xml zip resolved by exescorm_source).
• Full plugin PHPUnit suite green on Moodle 5.0.7 / PHP 8.3 (368 tests, 1311 assertions, 0 failures/errors).
• php -l and phpcs --standard=moodle clean on all changed/added files.

Known limitations

• The embedded-.elpx case is validated by extension (the nested zip is not opened during the cheap preflight); the extractor's index.html guard is the backstop.
• Source-less SCORM packages and plain web exports (no content.xml) are intentionally not preserved as static content — they cannot be reconstructed as editable eXeLearning activities. Offering such preservation would be a separate product decision.

Research notes

See research/analisis/notas/AN-015-deteccion-content-xml-migracion.md (Spanish) for the analysis of what each legacy plugin stores, the content.xml criterion and verdict table, the rationale for excluding legacy .elp/source-less packages, and the test matrix.

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Moodle Playground Preview

The changes in this pull request can be previewed and tested using a Moodle Playground instance.

ℹ️ The eXeLearning editor is fetched from the shared release and unpacked into the plugin when the playground boots, so the first load may take a few extra seconds. ELPX upload, viewer and preview work normally.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.07843% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.51%. Comparing base (06c53c4) to head (ad30ba7).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
classes/local/migration/source/package_probe.php	94.28%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #89      +/-   ##
============================================
+ Coverage     89.49%   89.51%   +0.02%     
- Complexity      976      980       +4     
============================================
  Files            52       53       +1     
  Lines          4236     4236              
============================================
+ Hits           3791     3792       +1     
+ Misses          445      444       -1     

Flag	Coverage Δ
javascript	94.03% <ø> (ø)
php	89.35% <96.07%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
PHP (server-side)	89.35% <96.07%> (+0.02%)	⬆️
JavaScript (SCORM tracker)	94.03% <ø> (ø)

Files with missing lines	Coverage Δ
classes/local/migration/source/exescorm_source.php	95.00% <100.00%> (+0.97%)	⬆️
classes/local/migration/source/exeweb_source.php	100.00% <100.00%> (+1.61%)	⬆️
classes/local/migration/source/package_probe.php	94.28% <94.28%> (ø)

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