fix(flet-lottie): local asset files not loading on Windows desktop

[ndonkoHenri]

When src="sample.json" is passed, Flet's getAssetSource() resolves it to an absolute filesystem path (e.g. C:\Users\...\assets\sample.json). flet-lottie was passing that path to Lottie.asset(...), which is the Flutter asset-bundle API — it looks up keys registered in pubspec.yaml at build time, not arbitrary filesystem paths. On Windows this surfaces as Unable to load asset: "C:\...".

As fix, we now route filesystem paths through Lottie.file(io.File(path)) instead, for better local file handling.

Resolves #6386

Test Code

import flet as ft
import flet_lottie as ftl


def main(page: ft.Page):
    page.add(
        ft.SafeArea(
            content=ft.Column(
                controls=[
                    ftl.Lottie(
                        src="https://raw.githubusercontent.com/xvrh/lottie-flutter/master/example/assets/Mobilo/A.json",
                        reverse=False,
                        animate=True,
                        error_content=ft.Placeholder(ft.Text("Error loading Lottie")),
                        on_error=lambda e: print(f"Error loading Lottie: {e.data}"),
                    ),
                    ftl.Lottie(
                        src="sample.json",
                        reverse=False,
                        animate=True,
                        enable_merge_paths=True,
                        enable_layers_opacity=True,
                        error_content=ft.Placeholder(ft.Text("Error loading Lottie")),
                        on_error=lambda e: print(f"Error loading Lottie: {e.data}"),
                    ),
                ],
            ),
        )
    )


if __name__ == "__main__":
    ft.run(main)

Summary by Sourcery

Route local Lottie JSON asset paths through a new file-based loader to fix desktop file loading issues and keep web builds compiling.

Bug Fixes:

• Resolve failures to load local Lottie JSON assets on Windows desktop (and intermittently on other desktop platforms) when referenced via src in the app assets directory.

Enhancements:

• Introduce a platform-aware fileLottie wrapper that uses Lottie.file for filesystem paths on IO platforms while providing a stub on web.
• Bump the lottie Flutter dependency from 3.3.2 to 3.3.3 in the flet-lottie package.

Documentation:

• Add a CHANGELOG entry for version 0.85.0 documenting the desktop local asset loading fix.

[sourcery-ai]

We've reviewed this pull request using the Sourcery rules engine

[Copilot]

Pull request overview

This PR fixes flet-lottie failing to load local Lottie JSON files on Windows desktop by switching local (filesystem) sources to use Lottie.file(...) instead of Flutter’s asset-bundle API (Lottie.asset(...)), which expects build-time registered assets.

Changes:

• Route AssetSource.isFile Lottie sources through a new fileLottie() helper that calls Lottie.file(...) on IO platforms.
• Add conditional export (file_lottie.dart) with an IO implementation and a web stub to keep web builds compiling.
• Bump the Flutter lottie dependency and add a changelog entry describing the fix.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
sdk/python/packages/flet-lottie/src/flutter/flet_lottie/pubspec.yaml	Updates lottie dependency version used by the Flutter side of flet-lottie.
sdk/python/packages/flet-lottie/src/flutter/flet_lottie/lib/src/lottie.dart	Switches local file loading from Lottie.asset to the new fileLottie() wrapper.
sdk/python/packages/flet-lottie/src/flutter/flet_lottie/lib/src/file_lottie.dart	Adds conditional export to select IO vs web implementation.
sdk/python/packages/flet-lottie/src/flutter/flet_lottie/lib/src/file_lottie_io.dart	Implements fileLottie() via Lottie.file(io.File(path)) for desktop/mobile.
sdk/python/packages/flet-lottie/src/flutter/flet_lottie/lib/src/file_lottie_web.dart	Provides a web stub (throws) to keep the package compiling on web.
sdk/python/packages/flet-lottie/CHANGELOG.md	Documents the fix under a new release entry.
client/pubspec.lock	Updates resolved dependency versions for the Flutter client workspace.

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