All pub command is unavailble after a pub add command

[Taoduhui]

Running pub upgrade...
Null check operator used on a null value
package:pub/src/system_cache.dart 50:52                SystemCache.defaultDir.<fn>
package:pub/src/system_cache.dart 60:5                 SystemCache.defaultDir
package:pub/src/system_cache.dart                      SystemCache.defaultDir
package:pub/src/system_cache.dart 98:42                new SystemCache
package:pub/src/command.dart 65:34                     PubCommand.cache
package:pub/src/command.dart                           PubCommand.cache
package:pub/src/command.dart 78:29                     PubCommand.entrypoint
package:pub/src/command.dart                           PubCommand.entrypoint
package:pub/src/command/upgrade.dart 112:25            UpgradeCommand.runProtected
package:pub/src/command.dart 190:45                    PubCommand.run.<fn>
dart:async                                             new Future.sync
package:pub/src/utils.dart 111:12                      captureErrors.wrappedCallback
dart:async                                             runZonedGuarded
package:pub/src/utils.dart 128:5                       captureErrors
package:pub/src/command.dart 190:13                    PubCommand.run
package:args/command_runner.dart 212:27                CommandRunner.runCommand
package:pub/src/command_runner.dart 176:24             PubCommandRunner.runCommand
package:pub/src/command_runner.dart 161:20             PubCommandRunner.run
package:dartdev/dartdev.dart 49:47                     runDartdev
C:\b\s\w\ir\x\w\sdk\pkg\dartdev\bin\dartdev.dart 11:9  main
An unexpected error was encountered by the Dart CLI.
Please file an issue at https://github.com/dart-lang/sdk/issues/new with the following details:

Invocation: 'dart __deprecated_pub upgrade --verbosity=error --no-precompile'
Exception: 'Null check operator used on a null value'
Stack Trace:
#0      SystemCache.defaultDir.<anonymous closure> (package:pub/src/system_cache.dart:50:52)
dart-lang/sdk#1      SystemCache.defaultDir (package:pub/src/system_cache.dart:60:5)
dart-lang/sdk#2      SystemCache.defaultDir (package:pub/src/system_cache.dart)
dart-lang/sdk#3      new SystemCache (package:pub/src/system_cache.dart:98:42)
dart-lang/sdk#4      PubCommand.cache (package:pub/src/command.dart:65:34)
dart-lang/sdk#5      PubCommand.cache (package:pub/src/command.dart)
dart-lang/sdk#6      PubCommand.transcriptPath (package:pub/src/command.dart:337:19)
dart-lang/sdk#7      PubCommand.run (package:pub/src/command.dart:204:6)
<asynchronous suspension>
dart-lang/sdk#8      CommandRunner.runCommand (package:args/command_runner.dart:212:13)
<asynchronous suspension>
dart-lang/sdk#9      PubCommandRunner.runCommand (package:pub/src/command_runner.dart:176:12)
<asynchronous suspension>
dart-lang/sdk#10     PubCommandRunner.run (package:pub/src/command_runner.dart:161:14)
<asynchronous suspension>
dart-lang/sdk#11     runDartdev (package:dartdev/dartdev.dart:49:18)
<asynchronous suspension>
dart-lang/sdk#12     main (file:///C:/b/s/w/ir/x/w/sdk/pkg/dartdev/bin/dartdev.dart:11:3)
<asynchronous suspension>

Error (255): Unable to 'pub upgrade' flutter tool. Retrying in five seconds... (5 tries left)

after i run pub add file_picker, all pub command will throw above error.
i try to repair it by pub clean and pub cache repair, looks no effect.
then i reinstall the dart sdk, no effect too.

[sigurdm]

@Taoduhui

• What version of flutter are you using?
• What version of windows?
• Did you do anything that would set the APPDATA environment variable?

The line that fails is:

pub/lib/src/system_cache.dart

Line 50 in 14b1310

var appData = Platform.environment['APPDATA']!;

Somehow you do not have a APPDATA variable defined in you environment.

According to https://stackoverflow.com/questions/59410900/can-the-appdata-environment-variable-ever-be-missing-on-windows this should only ever happen if you explicitly unset the APPDATA variable - could you have done that?

In the next release of flutter we no longer look into APPDATA (we prefer LOCALAPPDATA), and we give a nice error message if that is unset: #3831 so there this would not happen.

[sigurdm]

You can try running this command in the shell

SET

To list all environment variables. It should show APPDATA.

You can also try using the flutter beta channel to see if the fix works.

[Taoduhui]

Yes, as you said, I tried to reproduce the issue and found that it was caused by my proxy software clearing the APPDATA and LOCALAPPDATA environment variables.