Dart Resolve Package ConflictsSAFE

An agent skill published by flutter.

The instruction file, verbatim from the audited commit — this is the text the model reads, and the surface the audit's instruction layer examines. Quoted here so you can judge it without cloning anything.

---
name: dart-resolve-package-conflicts
description: Workflow for fixing package version conflicts. Use this when `pub get` fails due to incompatible package versions.
metadata:
  model: models/gemini-3.1-pro-preview
  last_modified: Fri, 24 Apr 2026 15:11:14 GMT
---
# Managing Dart Dependencies

## Contents
- [Core Concepts](#core-concepts)
- [Version Constraints](#version-constraints)
- [Workflow: Auditing Dependencies](#workflow-auditing-dependencies)
- [Workflow: Upgrading Dependencies](#workflow-upgrading-dependencies)
- [Workflow: Resolving Version Conflicts](#workflow-resolving-version-conflicts)
- [Examples](#examples)

## Core Concepts

Dart enforces a strict single-version rule for dependencies: a project and all its transitive dependencies must resolve to a single, shared version of any given package. This prevents runtime type mismatches but introduces the risk of "version lock."

To mitigate version lock, Dart relies on version constraints rather than pinned versions in the `pubspec.yaml`. The `pubspec.lock` file maintains the exact resolved versions for reproducible builds.

Understand the output columns of `dart pub outdated`:
*   **Current:** The version currently recorded in `pubspec.lock`.
*   **Upgradable:** The latest version allowed by the constraints in `pubspec.yaml`. `dart pub upgrade` resolves to this.
*   **Resolvable:** The absolute latest version that can be resolved when factoring in all other dependencies in the project.
*   **Latest:** The latest published version of the package (excluding prereleases).

## Version Constraints

*   **Use Caret Syntax:** Always use caret syntax (e.g., `^1.2.3`) for dependencies in `pubspec.yaml`. This allows `pub` to select newer, non-breaking versions (up to, but not including, the next major version) during resolution.
*   **Tighten Dev Dependencies:** Set the lower bound of `dev_dependencies` to the exact version currently used. This reduces resolution complexity and prevents older, incompatible dev tools from being selected.
*   **Enforce Lockfiles in CI:** Use `dart pub get --enforce-lockfile` in CI/CD pipelines to ensure the exact versions tested locally are used in production.

## Workflow: Auditing Dependencies

Run this workflow periodically to identify stale packages that may impact stability or performance.

**Task Progress:**
- [ ] Run `dart pub outdated`.
- [ ] Review the **Upgradable** column to identify packages that can be updated without modifying `pubspec.yaml`.
- [ ] Review the **Resolvable** column to identify packages that require constraint modifications in `pubspec.yaml` to update.
- [ ] Identify any packages marked as retracted or discontinued.

## Workflow: Upgrading Dependencies

Use conditional logic based on the audit results to upgrade dependencies.

**Task Progress:**
- [ ] **If updating to "Upgradable" versions:**
  - [ ] Run `dart pub upgrade`.
  - [ ] Run `dart pub upgrade --tighten` to automatically update the lower bounds in `pubspec.yaml` to match the newly resolved versions.
- [ ] **If updating to "Resolvable" versions (Major updates):**
  - [ ] Manually edit `pubspec.yaml` to bump the version constraint to match the "Resolvable" column (e.g., change `^0.11.0` to `^0.12.1`).
  - [ ] Run `dart pub upgrade` to resolve the new constraints and update `pubspec.lock`.
- [ ] **Feedback Loop:**
  - [ ] Run `dart analyze` -> review errors -> fix breaking API changes.
  - [ ] Run `dart test` -> review failures -> fix regressions.

## Workflow: Resolving Version Conflicts

When `pub` cannot find a set of concrete versions that satisfy all constraints, or when dealing with a retracted package version, manipulate the lockfile surgically.

**NEVER** delete the entire `pubspec.lock` file and run `dart pub get`. This causes uncontrolled upgrades across the entire dependency graph.

**Task Progress:**
- [ ] Open `pubspec.lock`.
- [ ] Locate the specific YAML block for the conflicting or retracted package.
- [ ] Delete ONLY that package's entry from the lockfile.
- [ ] Run `dart pub get` to fetch the newest compatible, non-retracted version for that specific package.
- [ ] **Feedback Loop:**
  - [ ] Run `dart pub deps` -> verify the dependency graph resolves correctly.
  - [ ] If resolution fails, identify the transitive dependency causing the lock, update its constraint in `pubspec.yaml`, and retry.

## Examples

### Tightening Constraints
When `dart pub outdated` shows a package is resolvable to a higher minor/patch version, use the `--tighten` flag to update the `pubspec.yaml` automatically.

**Input (`pubspec.yaml`):**
```yaml
dependencies:
  http: ^0.13.0
```

**Command:**
```bash
dart pub upgrade --tighten http
```

**Output (`pubspec.yaml`):**
```yaml
dependencies:
  http: ^0.13.5
```

### Surgical Lockfile Removal
If `package_a` is retracted or locked in a conflict, remove only its block from `pubspec.lock`.

**Before (`pubspec.lock`):**
```yaml
packages:
  package_a:
    dependency: "direct main"
    description:
      name: package_a
      url: "https://pub.dev"
    source: hosted
    version: "1.0.0" # Retracted version
  package_b:
    dependency: "direct main"
    # ...
```

**Action:** Delete the `package_a` block entirely. Leave `package_b` untouched. Run `dart pub get`.

SAFEgrade B · trust 89/100 Nothing in the source contradicts what it says it does. Grade A is reserved for packages that have also passed the behavioural sandbox.

What the source does

Filesystem

none-observed

Network

none-observed

Shell

none-observed

Dependencies

pinned

Secrets in source

none-found

Findings (0)

No findings outside the package's declared scope.

Gates applied: no_behavioural_pass.

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