Aspect Ordering & Precedence Rules

Ordering Rules

1. Aspects execute in ascending order - AspectExpansionProcessor sorts applicable aspects with Comparator.comparingInt(PipelineAspectModel::order) and appends synthetic steps in that sorted order.

2. Lower order executes earlier - For both BEFORE_STEP and AFTER_STEP, lower order values are emitted earlier than higher order values.

3. Same position chaining - If multiple aspects target the same position, BEFORE_STEP aspects execute before the step in ascending order, and AFTER_STEP aspects execute after the step in ascending order. This follows the AspectExpansionProcessor sort-and-append logic directly.

4. Default order is 0 - If no order is specified, aspects default to order 0.

5. Tie-breaking - When multiple aspects share the same order and position, execution order is deterministic but unspecified; implementations MUST preserve declaration order.

6. Order is signed - Order is a signed integer. Negative values are allowed and execute before zero-valued aspects.

7. Position precedence - BEFORE_STEP aspects always execute before the step, and AFTER_STEP aspects always execute after the step, regardless of order value.

Example

Consider these aspects applied to a single step:

• Aspect A: position=BEFORE_STEP, order=10
• Aspect B: position=BEFORE_STEP, order=5
• Aspect C: position=AFTER_STEP, order=0
• Aspect D: position=AFTER_STEP, order=1

The execution order would be:

1. Aspect B executes (BEFORE_STEP, order=5)
2. Aspect A executes (BEFORE_STEP, order=10)
3. Actual step executes
4. Aspect C executes (AFTER_STEP, order=0)
5. Aspect D executes (AFTER_STEP, order=1)

This creates the following logical pipeline:

Input -> Aspect B -> Aspect A -> Step -> Aspect C -> Aspect D -> Output