Илия a634f089ab
Improve Container color/decoration error message clarity (#178823)
## Description

This PR improves the clarity of the error message shown when developers
provide both `color` and `decoration` parameters to a `Container`
widget.

### Problem

The previous assertion message was confusing and contradictory:
```
Cannot provide both a color and a decoration
To provide both, use "decoration: BoxDecoration(color: color)".
```

This message stated "Cannot provide **both**" but then suggested "To
provide **both**, use...", which confused developers about the actual
requirement. The suggestion appeared to offer a workaround to use both
parameters together, when in fact it was explaining how to migrate from
using `color` to using `decoration` exclusively.

### Solution

Updated the assertion message to clearly explain:
- The `color` parameter is a shorthand for `decoration:
BoxDecoration(color: color)`
- Developers should use **either** `color` OR `decoration`, not both
- To use both a color and other decoration properties (like borders,
shadows, etc.), set the color within the `BoxDecoration` instead

**New message:**
```
Cannot provide both a color and a decoration.
The color argument is just a shorthand for "decoration: BoxDecoration(color: color)".
To use both a color and other decoration properties, set the color in the BoxDecoration instead.
```

## Related Issues

Fixes #119484

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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[test-exempt]:
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[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

Co-authored-by: Tong Mu <dkwingsmt@users.noreply.github.com>
2025-12-31 00:08:37 +00:00
..
2025-12-19 23:45:25 +00:00