Optimize modules dict iteration with early return when empty

[enjoy-binbin]

Avoid dictIterator allocation overhead by checking dictSize(modules) == 0
in all functions that iterate over the modules dictionary, returning early
with the appropriate default value.

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR adds early-exit checks across the modules subsystem: when the modules dictionary is empty, 12 functions now return immediately with appropriate empty results (NULL, 0, C_OK, or input value), avoiding iterator creation and per-module loops in config loading, type lookup, capability verification, persistence, info collection, and lifecycle operations.

Changes

Early-exit optimization across modules subsystem for empty module dictionary

Layer / File(s)	Summary
Config module-loading early-exit src/config.c	rewriteConfigLoadmoduleOption() checks if modules is empty, marks loadmodule option processed, and returns immediately, skipping iterator creation.
Module type lookup early-exits src/module.c	moduleTypeLookupModuleByNameInternal() and moduleTypeLookupModuleByID() return NULL immediately when modules is empty, avoiding cache traversal and iterator setup.
Module capability verification early-exits src/module.c	moduleAllDatatypesHandleErrors(), moduleAllModulesHandleReplAsyncLoad(), and moduleVerifyAllAllowAtomicSlotMigrationOrReply() return their appropriate empty-case values immediately when modules is empty.
Module persistence and info collection early-exits src/module.c	rdbSaveModulesAux(), modulesCollectInfo(), and genModulesInfoString() return immediately with appropriate empty results when modules is empty, skipping iteration loops.
Module lifecycle and reply early-exits src/module.c	moduleUnloadAllModules() returns immediately, addReplyLoadedModules() sends empty array and returns, and moduleDefragGlobals() returns immediately when modules is empty.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 76.92% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description is directly related to the changeset, explaining the optimization approach of checking dictSize(modules) == 0 and returning early across modules iteration.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title accurately describes the main optimization implemented throughout the pull request: adding early-return checks when the modules dictionary is empty to avoid iterator creation and loops.

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[codecov]

Codecov Report

❌ Patch coverage is 68.75000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.73%. Comparing base (436dcae) to head (b9230f9).
⚠️ Report is 11 commits behind head on unstable.

Files with missing lines	Patch %	Lines
src/module.c	76.92%	3 Missing ⚠️
src/config.c	33.33%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #4002      +/-   ##
============================================
- Coverage     76.75%   76.73%   -0.02%     
============================================
  Files           162      162              
  Lines         81017    81035      +18     
============================================
- Hits          62187    62185       -2     
- Misses        18830    18850      +20     

Files with missing lines	Coverage Δ
src/config.c	78.84% <33.33%> (-0.09%)	⬇️
src/module.c	25.44% <76.92%> (+0.12%)	⬆️

... and 22 files with indirect coverage changes

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