implement-flet-extension

name	implement-flet-extension
description	Implement a new Flet extension/control that wraps a third-party Flutter package end-to-end, including dependency selection, version pinning, compatibility checks, Python/Flutter integration, docs, examples, tests, and CI updates. Use when adding any flet_* package backed by an external pub.dev package. Use when this capability is needed.
metadata	{"author":"flet-dev"}

Implement a Flet extension around an external Flutter package using existing flet_* packages as implementation templates.

Inputs

• Control/service name and Python package name (flet_<extension>).
• Target pub.dev package and intended version/range.
• API surface to expose in Python (properties, methods, events, types/enums).

Third-party Dependency Gate

1. Confirm package health: maintenance activity, null-safety, platform support, and open issue risk.
2. Confirm license is compatible with Flet distribution.
3. Select a conservative version strategy:

• Pin exact version when behavior stability is critical.
• Use bounded ranges when required by ecosystem constraints.

4. Record key constraints and reasons in PR notes/commit message.

Control/Service Classification

• Classify wrapped functionality before implementation:

1. LayoutControl for visual controls that participate in page/layout positioning.
2. Base Control for simple visual controls that do not require page positioning or define their own positioning rules/props (for example Draggable, Divider, MenuBar, NavigationRail).
3. Non-visual Service when functionality is not a renderable UI control.

• Inspect the wrapped Flutter package API to determine whether it includes non-visual/service functionality.
• For service patterns, follow existing extension examples: sdk/python/packages/flet-audio, sdk/python/packages/flet-flashlight, sdk/python/packages/flet-secure-storage.

API Mapping Rules

• Expose only stable and useful features first; avoid mirroring every upstream option.
• Keep Python API idiomatic and concise; avoid redundant control-name prefixes.
• Map upstream naming inconsistencies to Flet conventions when needed.
• Add custom enums/types only when they improve correctness and discoverability.

Python-side Rules

• Use LayoutControl, base Control, or Service base class according to classification.
• Implement typed properties, methods, and events exactly for chosen public API.
• Reuse existing serialization/event patterns from sibling controls/services.

Flutter-side Rules

• Use parseEnum() for enums.
• For control attributes, prefer widget.control.getBool()/getDouble()/... accessors.
• For non-control parsing, use shared parseSomething() helpers.
• Do not add one-off private parser utilities when standard helpers exist.
• Put control-specific helpers in utils/<control>.dart; shared helpers in utils/<topic>.dart.
• Prefer parse-prefixed helper names when converting input to Flutter structures.
• Avoid single-use local variables.

Default Value Matching (Critical)

Properties with default values on the Python side are not sent to Flutter when unchanged from the default. Every Dart property read must provide the same default as its Python counterpart:

• control.getDouble("size", 100.0)! when Python has size: float = 100.0
• control.getBool("animate", true)! when Python has animate: bool = True
• parseDuration(value["dur"], const Duration(milliseconds: 500))! when Python has dur: DurationValue = field(default_factory=lambda: Duration(milliseconds=500))
• control.get<List>("items")?.map(...).toList() ?? const [] when Python has items: list[str] = field(default_factory=list)

Without matching defaults, Dart receives null and either crashes or silently uses the wrong value. This applies to all property types: bools, numbers, strings, enums, durations, collections, and nested @ft.value types.

Integration Checklist

• Add dependency and registration to Flet client app.
• Add extension package to sdk/python/pyproject.toml.
• Add extension to sdk/python/packages/flet/pyproject.toml.
• Add extension to sdk/python/examples/apps/flet_build_test/pyproject.toml.
• Add extension to .github/workflows/ci.yml in both places:
  • build_flet_extensions -> PACKAGES list.
  • py_publish -> for pkg in ... publish loop.
• Add .gitignore to Flutter extension project if missing.

Docs, Examples, Tests

• Add control/service docs under website/docs/controls/<name> for controls and website/docs/services/<name> for services.
• Add all custom enums/types docs and update website/sidebars.yml navigation.
• Use markdown filenames without underscores (codeeditor.md, not code_editor.md).
• Add examples under sdk/python/examples in the appropriate category for control vs service.
• Add integration tests under packages/flet/integration_tests in the appropriate category for control vs service.
• Ensure generated screenshots are suitable for docs usage when visual examples are added.

Upgrade and Compatibility Guardrails

• Add at least one test that catches upstream behavioral changes likely to break wrapper mapping.
• Avoid exposing experimental upstream APIs unless explicitly requested.
• Keep wrapper surface narrow enough to maintain backwards compatibility across upstream updates.

Validation

• Run relevant Python and integration tests for touched areas.
• Verify Python import paths, client runtime registration, and docs navigation.
• Verify dependency resolution and lockfile updates are intentional.

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