🐛 Map: restore .item as deprecated alias

[GeigerJ2]

TL;DR Restore Map.item (and the placeholder kwarg) as deprecated aliases so 0.9.0 doesn't break 0.8.1 downstream.

#792 dropped map_zone.item for .value/.key, reasoning "with no stable release, z.item is dropped outright." But v0.8.1 shipped .item, so that removed a released public API with no deprecation, and 0.8.1 code using map_zone.item.value/.key breaks on upgrade.

Ahead of the 0.9.0 release:

• Map.item returns the map-item outputs namespace again, emitting a DeprecationWarning pointing to .value/.key, and resolving to the same sockets.
• Map(source, placeholder=...) accepts placeholder again, ignored with a warning, so a 0.8.1-style call doesn't TypeError (it's been a no-op since Update map #510).

Tests assert both aliases still work and warn.

From a v0.8.1..main audit, .item was the only user-facing public break in the 17 PRs since 0.8.1. The one non-shimmable change is #787's stricter task-name validation (intentional; only affects non-identifier task names).

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📥 Commits

Reviewing files that changed from the base of the PR and between 32ea9af and 96a0a0a.

📒 Files selected for processing (3)

• src/aiida_workgraph/manager.py
• src/aiida_workgraph/tasks/builtins.py
• tests/test_map.py

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📝 Walkthrough

Walkthrough

The Map API now accepts the deprecated placeholder argument with a warning. The Map.item property restores the deprecated socket alias with a warning. Tests verify both compatibility paths.

Changes

Map API compatibility

Layer / File(s)	Summary
Placeholder argument compatibility src/aiida_workgraph/manager.py, tests/test_map.py	Map accepts the deprecated placeholder keyword, ignores its value, and emits a DeprecationWarning.
Deprecated item socket alias src/aiida_workgraph/tasks/builtins.py, tests/test_map.py	Map.item returns the map-item outputs namespace and emits a DeprecationWarning. Tests compare its sockets with Map.value and Map.key.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 96a0a

The change restores deprecated Map aliases while preserving existing key/value behavior and warning callers to migrate; no actionable merge-blocking risk remains after normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the backward-compatibility changes to Map.item and the placeholder keyword, including the deprecation behavior and tests.
Title check	✅ Passed	The title clearly identifies the main change: restoring Map.item as a deprecated alias. It is concise and directly related to the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 85.71% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 3 files.
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.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.96%. Comparing base (32ea9af) to head (96a0a0a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #815      +/-   ##
==========================================
+ Coverage   90.94%   90.96%   +0.03%     
==========================================
  Files          46       46              
  Lines        3199     3207       +8     
==========================================
+ Hits         2909     2917       +8     
  Misses        290      290              

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