FOEPD-1417 fix pipeline type from/to json

[swheaton]

What changes are proposed in this pull request?

Pipeline type was messed up on-disk in a way that unit tests didn't catch but voxelhub did. This fixes that discrepancy.

How is this patch tested? If it is not, please explain why.

Added more unit tests

Release Notes

Is this a user-facing change that should be mentioned in the release notes?

• No. You can skip the rest of this section.
• Yes. Give a description of this change to be included in the release
  notes for FiftyOne users.

What areas of FiftyOne does this PR affect?

• App: FiftyOne application changes
• Build: Build and test infrastructure changes
• Core: Core fiftyone Python library changes
• Documentation: FiftyOne documentation changes
• Other

Summary by CodeRabbit

• Refactor

  • Pipeline JSON format changed to an object with a "stages" field instead of a plain list; serialization and deserialization use this shape and default to an empty "stages" list when absent.

• Tests

  • Added and updated unit tests for pipeline and stage creation, ordering, serialization/deserialization, round-trip behavior, and validation (e.g., missing operator, non-positive distributed task counts).

[coderabbitai]

Walkthrough

Pipeline JSON shape changed from a list to a dict with a top-level "stages" key; Pipeline.from_json now accepts that dict and Pipeline.to_json returns {"stages": [...]}. Unit tests added for Pipeline/PipelineStage creation, staging, serialization round-trip, and validation errors.

Changes

Cohort / File(s)	Summary
Pipeline JSON contract change fiftyone/operators/_types/pipeline.py	from_json signature changed to accept a dict and read stages from json_dict.get("stages", []); to_json now returns a dict {"stages": [...]} (previously a list); docstrings/examples updated; serialization uses dataclasses.asdict(self).
Operator types unit tests tests/unittests/operators/types_tests.py	Added tests covering Pipeline and PipelineStage construction, staging order via constructor and .stage(), serialization (to_json) and deserialization (from_json) with the new dict format, and validation errors for missing or invalid operator_uri and num_distributed_tasks.
Factory doc test adjustment tests/unittests/factory/delegated_operation_doc_tests.py	Updated assertion to compare the serialized pipeline field against op_doc.pipeline.to_json() instead of manual per-element dicts, reflecting the canonical pipeline JSON representation and preserving round-trip comparison via from_pymongo.

Sequence Diagram(s)

sequenceDiagram
    participant Client
    participant Pipeline
    participant JSON as "JSON Dict\n{\"stages\": [...]}"

    Note over Pipeline,JSON: Serialization (new shape)
    Client->>Pipeline: to_json()
    Pipeline-->>Client: {"stages": [ stage_json, ... ]}

    Note over Pipeline,JSON: Deserialization (new input)
    Client->>Pipeline: from_json({"stages": [ stage_json, ... ]})
    Pipeline-->>Client: Pipeline(stages=[...])

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

A rabbit taps keys with a curious hop,
Packing stages tidy in one little top—
"stages" in a dict, neat rows in a line,
Tests sniff and hop, then give them a sign.
Hooray for small changes that make JSON fine. 🥕

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title Check	✅ Passed	The title succinctly highlights the primary change—fixing the Pipeline type’s JSON serialization and deserialization—and directly relates to the core update in the changeset. It is concise, clear, and focused on the main purpose of the pull request.
Description Check	✅ Passed	The pull request description follows the repository template by including the required headings for proposed changes, testing details, release notes, and affected areas, and each section is properly filled out with relevant information.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/foepd-1417-fix-pipeline-type

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📥 Commits

Reviewing files that changed from the base of the PR and between e6a90d8 and 5240c39.

📒 Files selected for processing (2)

• fiftyone/operators/_types/pipeline.py (1 hunks)
• tests/unittests/factory/delegated_operation_doc_tests.py (1 hunks)

🔇 Additional comments (3)

fiftyone/operators/_types/pipeline.py (2)

117-130: LGTM!

The implementation correctly uses dataclasses.asdict(self) to produce the dict format with "stages" key. This is clean and maintainable.

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99-115: LGTM! Verify all call sites are updated.

The implementation correctly handles the new dict format with a "stages" key. The use of json_dict.get("stages") or [] properly handles missing keys and None values, and PipelineStage validation will catch invalid stage data.

However, since this is a breaking API change (from accepting a list to accepting a dict), ensure all call sites have been updated accordingly.

Run the following script to verify all call sites of Pipeline.from_json() are passing a dict:

tests/unittests/factory/delegated_operation_doc_tests.py (1)

72-72: LGTM! Improved test maintainability.

Excellent change to use op_doc.pipeline.to_json() instead of manually constructing the expected dict. This makes the test more maintainable and accurately tests the actual serialization output. The round-trip verification on line 75 ensures deserialization works correctly.

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[CamronStaley]