Add assign_child_by_anchor method for anchor-based resource assignment

[rickwierenga]

Summary

Adds a new assign_child_by_anchor() method to the Resource class that allows assigning child resources by aligning anchor points instead of specifying absolute coordinates. This provides a more intuitive and flexible way to position resources relative to each other.

Key Features

• Anchor-based alignment: Align any combination of anchors (left/center/right, front/center/back, bottom/center/top)
• Dual syntax support:
  • Tuple syntax: parent_anchor=("c", "c", "b")
  • String syntax: parent_anchor="ccb" (more concise)
• Default behavior: Defaults to left-front-bottom (LFB) alignment
• Full integration: Maintains all existing callbacks, validation, and reassignment logic

Example Usage

# Default: align LFB of both resources
parent.assign_child_by_anchor(child)

# Center a child resource
parent.assign_child_by_anchor(child, parent_anchor="ccb", child_anchor="ccb")

# Stack resources on top of each other
parent.assign_child_by_anchor(child, parent_anchor="lft", child_anchor="lfb")

Implementation Details

• Added helper function _compute_location_from_anchors() to calculate the location from anchor specifications
• Method internally calls assign_child_resource() with computed location
• Supports validation of string anchor length (must be exactly 3 characters)
• Uses named arguments for clarity

Test Plan

• 17 comprehensive unit tests added covering:
  • Default LFB alignment
  • All x, y, and z anchor combinations (27 subtests)
  • Center-center-bottom alignment
  • Corner alignments (LFB, RBT)
  • Stacking operations
  • Mixed anchor combinations
  • String and tuple syntax
  • Mixed string/tuple usage
  • Long-form anchor names ("center" vs "c")
  • Invalid string anchor length handling
  • Reassignment between parents
  • Callback triggering
• All 48 resource tests pass
• Pre-commit hooks pass (formatting, linting)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR adds a new assign_child_by_anchor() method to the Resource class that enables anchor-based positioning of child resources, providing a more intuitive alternative to calculating absolute coordinates manually.

Changes:

• Added _compute_location_from_anchors() helper function to calculate relative locations from anchor specifications
• Added assign_child_by_anchor() method supporting both tuple ("l", "f", "b") and string "lfb" anchor syntax
• Added 17 comprehensive unit tests covering all anchor combinations, syntax variations, and edge cases

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
pylabrobot/resources/resource.py	Added _compute_location_from_anchors() helper and assign_child_by_anchor() method with dual syntax support for anchor-based child resource assignment
pylabrobot/resources/resource_tests.py	Added TestAssignChildByAnchor test class with 17 comprehensive tests covering all anchor combinations, syntax variations, reassignment, and callbacks

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