Validate `PUB_HOSTED_URL` variable format

[dongfuting]

Running "flutter packages upgrade" in flutter_app...
Illegal scheme character (at character 7)
export PUB_HOSTED_URL=https://pub.flutter-io.cn/api/packages/cupertino_icons
^
dart:core Uri.parse
package:pub/src/source/hosted.dart 165:16 BoundHostedSource._makeUrl
package:pub/src/source/hosted.dart 132:15 BoundHostedSource.doGetVersions
===== asynchronous gap ===========================
package:pub/src/source.dart 167:12 BoundSource.getVersions
package:pub/src/solver/package_lister.dart 76:44 PackageLister._versions..
dart:async runZoned
package:pub/src/http.dart 272:10 withDependencyType
package:pub/src/solver/package_lister.dart 75:33 PackageLister._versions.
===== asynchronous gap ===========================
dart:async new Future.sync
package:async/src/async_memoizer.dart 43:42 AsyncMemoizer.runOnce
package:pub/src/solver/package_lister.dart 74:58 PackageLister._versions
package:pub/src/solver/package_lister.dart 111:21 PackageLister.countVersions
===== asynchronous gap ===========================
package:pub/src/solver/version_solver.dart 354:44 VersionSolver._choosePackageVersion.
===== asynchronous gap ===========================
package:pub/src/utils.dart 301:39 minByAsync
===== asynchronous gap ===========================
package:pub/src/solver/version_solver.dart 350:25 VersionSolver._choosePackageVersion
===== asynchronous gap ===========================
package:pub/src/solver/version_solver.dart 97:22 VersionSolver.solve
===== asynchronous gap ===========================
package:pub/src/solver.dart 35:10 resolveVersions.
package:pub/src/log.dart 378:18 progress
package:pub/src/solver.dart 32:10 resolveVersions
package:pub/src/entrypoint.dart 200:24 Entrypoint.acquireDependencies
===== asynchronous gap ===========================
package:pub/src/command/upgrade.dart 43:22 UpgradeCommand.run
===== asynchronous gap ===========================
package:args/command_runner.dart 194:27 CommandRunner.runCommand
===== asynchronous gap ===========================
package:pub/src/command_runner.dart 168:39 PubCommandRunner.runCommand.
dart:async new Future.sync
package:pub/src/utils.dart 109:12 captureErrors.
dart:async runZoned
package:pub/src/utils.dart 126:5 captureErrors
package:pub/src/command_runner.dart 168:13 PubCommandRunner.runCommand
===== asynchronous gap ===========================
package:pub/src/command_runner.dart 117:11 PubCommandRunner.run
===== asynchronous gap ===========================
E:\b\build\slave\Windows_Engine\build\src\third_party\dart\third_party\pkg\pub\bin\pub.dart 8:22 main
This is an unexpected error. Please run

pub --trace --verbosity=warning upgrade --no-precompile

and include the logs in an issue on https://github.com/dart-lang/pub/issues/new

pub upgrade failed (65)
Process finished with exit code 65

[natebosch]

@dongfuting - it looks like you've configured the PUB_HOSTED_URL to be the entire command to set the environment variable, not the value of the variable itself. You might want to look up how to set environment variables on your OS. I think you'll want the value to be https://pub.flutter-io.cn/ and not the full URI you have in your example since that points to a specific package.

@mit-mit - I've been seeing this flavor of issue crop up a lot. A while back I added a little more validation before using this evironment variable but it looks like there is more we can do, and probably can handle it with a nicer error message and a link to some instructions. This might be something we should prioritize soon.

[mit-mit]

cc @jonasfj

[mit-mit]

cc @natebosch did you not add this already in #1972 ?

[natebosch]

I think that what I added in #1972 was incomplete, I handled some malformed config, but I think we need to catch a FormatException thrown by Uri.parse.

[mit-mit]

OK, maybe @jonasfj can help with that?

[sigurdm]

I believe this was fixed in #3030