dart pub downgrade

Downgrade is one of the commands of the pub tool.

$ dart pub downgrade [--[no-]offline] [-n|--dry-run] [dependencies...]

Without any additional arguments, dart pub downgrade gets the lowest versions of all the dependencies listed in the pubspec.yaml file in the current working directory, as well as their transitive dependencies. For example:

$ dart pub downgrade
Resolving dependencies... (1.2s)
+ barback 0.13.0
+ collection 0.9.1
+ path 1.2.0
+ source_maps 0.9.0
+ source_span 1.0.0
+ stack_trace 0.9.1
Changed 6 dependencies!

The dart pub downgrade command creates a lockfile. If one already exists, pub ignores that file and generates a new one from scratch, using the lowest versions of all dependencies.

See the dart pub get documentation for more information on package resolution and the system package cache.

It's possible to tell dart pub downgrade to downgrade specific dependencies to the lowest version while leaving the rest of the dependencies alone as much as possible. For example:

$ dart pub downgrade test
Resolving dependencies...
  barback 0.15.2+2
  bot 0.27.0+2
  browser 0.10.0+2
  chrome 0.6.5
  collection 1.1.0
  path 1.3.0
  pool 1.0.1
  source_span 1.0.2
< stack_trace 0.9.2 (was 1.1.1)
  stagexl 0.10.2
< test 0.10.0 (was 0.11.4)
These packages are no longer being depended on:
- matcher 0.11.3
Changed 3 dependencies!

If you are downgrading a specific dependency, pub tries to find the highest versions of any transitive dependencies that fit the new dependency constraints. Any transitive dependencies are usually also downgraded as a result.

If a dependency is added to the pubspec before dart pub downgrade is run, it gets the new dependency and any of its transitive dependencies. This shares the same behavior as dart pub get.

If a dependency is removed from the pubspec before dart pub downgrade is run, the dependency is no longer available for importing. Any transitive dependencies of the removed dependency are also removed, as long as no remaining immediate dependencies also depend on them. This is the same behavior as dart pub get.

If you don't have network access, you can still run dart pub downgrade. Because pub downloads packages to a central cache shared by all packages on your system, it can often find previously downloaded packages without needing to use the network.

However, by default, dart pub downgrade tries to go online if you have any hosted dependencies. If you don't want pub to do that, pass it the --offline flag. In offline mode, pub looks only in your local package cache, trying to find a set of versions that work with your package from what's already available.

For options that apply to all pub commands, see Global options.

By default, pub connects to the network to retrieve hosted packages (--no-offline). To use cached packages instead, use --offline. For details, see Getting while offline.

Reports what dependencies would change but doesn't change any.