[Windows]: Null Safety Migration tool 404 error

[iqfareez]

Error occurred when trying to migrate old Flutter project.

Steps to Reproduce

1. Create a new Flutter project

flutter create migration_error

2. Open pubspec.yaml and change the enviroment sdk to

sdk: ">=2.7.0 <3.0.0"

This is needed to disable null safety feature.
3. Make minor changes to main.dart
4. Run

dart migrate

Expected results:

Normal migration page

Actual results:

NNBD Migration Preview with 404 error.

Logs

Migrating D:\Iqmal\Documents\Flutter apps\Experiments\migration_error

See https://dart.dev/go/null-safety-migration for a migration guide.


Generating migration suggestions...
[--------------------------------------------------------------------------------------------------------------------]
Compiling instrumentation information...
[--------------------------------------------------------------------------------------------------------------------]
View the migration suggestions by visiting:
  http://127.0.0.1:61335/D:/Iqmal/Documents/Flutter%20apps/Experiments/migration_error?authToken=XE0nxcea0AQ%3D

Use this interactive web view to review, improve, or apply the results.
When finished with the preview, hit ctrl-c to terminate this process.

If you make edits outside of the web view (in your IDE), use the 'Rerun from
sources' action.

[√] Flutter (Channel stable, 2.10.3, on Microsoft Windows [Version
    10.0.22000.556], locale en-MY)
    • Flutter version 2.10.3 at C:\src\flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 7e9793dee1 (13 days ago), 2022-03-02 11:23:12 -0600
    • Engine revision bd539267b4
    • Dart version 2.16.1
    • DevTools version 2.9.2

[√] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at C:\Users\Iqmal\AppData\Local\Android\Sdk
    • Platform android-31, build-tools 30.0.3
    • ANDROID_HOME = C:\Users\Iqmal\AppData\Local\Android\Sdk
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 11.0.11+9-b60-7590822)
    • All Android licenses accepted.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe

[√] Visual Studio - develop for Windows (Visual Studio Community 2019 16.11.10)
    • Visual Studio at C:\Program Files (x86)\Microsoft Visual
      Studio\2019\Community
    • Visual Studio Community 2019 version 16.11.32126.315
    • Windows 10 SDK version 10.0.19041.0

[√] Android Studio (version 2021.1)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin can be installed from:
       https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
       https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 11.0.11+9-b60-7590822)

[√] IntelliJ IDEA Community Edition (version 2021.2)
    • IntelliJ at D:\Program Files\IntelliJ IDEA Community Edition 2021.2
    • Flutter plugin version 61.2.4
    • Dart plugin version 212.4746.57

[√] VS Code, 64-bit edition (version 1.65.1)
    • VS Code at C:\Program Files\Microsoft VS Code
    • Flutter extension version 3.36.0

[√] Connected device (3 available)
    • Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version
      10.0.22000.556]
    • Chrome (web)      • chrome  • web-javascript • Google Chrome 99.0.4844.51
    • Edge (web)        • edge    • web-javascript • Microsoft Edge 99.0.1150.39

[√] HTTP Host Availability
    • All required HTTP hosts are available

• No issues found!

[mattetti]

Quick workaround until there is a fix: edit the URL and change your Windows drive letter from d: to D: (from lowercase to uppercase), the tool doesn't seem to be able to load the repo if the drive letter is lowercase.

[iqfareez]

That works! Cheers man. In the terminal it shows the correct D:, then why in the browser it changed to d:? 🤔

[darshankawar]

@iqfareez
I tried replicating the use case you reported, but was unable to see the error. I get below as expected after accessing the link generated:

I verified this on same stack as you, ie, on Windows 10 and used latest stable 2.10.3.

The path is correctly captured by the tool, but not sure in your case, how did it get converted int lowercase d:

Do you consistently get the error everytime or was it one-off ?

I also see that you have space in your folder name D:\Iqmal\Documents\Flutter apps\Experiments\migration_errorD:\Iqmal\Documents\Flutter apps\Experiments\migration_error.

Can you remove the space and have FlutterApps instead and try again to see if the error still replicates ?

[iqfareez]

Thank you for your reply.

Actually, I'm on Windows 11.

I tried your suggestion, and the problem still exists. However, I think it is the vscode terminal fault. I run dart migrate on standalone cmd, and the link can open correctly.

Can you confirm by try to run it on vscode integrated terminal?

[darshankawar]

Thanks for the update. I don't use vscode so can't verify it.
Per your comment, since this is happening using vscode, I suggest you to open this issue in dedicated repo: https://github.com/Dart-Code/Dart-Code/issues and see what they say. I'll keep this issue open mean time.

[mattetti]

For what it's worth, i did repro on Windows 11, Dart 2.16 and VSCode. I clicked the link from the powershell terminal after running dart migrate.

[darshankawar]

Thanks for the feedback @mattetti. Although I don't have Windows 11, but I'll again try to replicate this using VSCode and check.

[iqfareez]

I suggest you to open this issue in dedicated repo: https://github.com/Dart-Code/Dart-Code/issues and see what they say.

I don't think it is related to the plugin. Nevertheless, I've opened an issue in vscode microsoft/vscode#145195. Let's hear what they will say about it.

But, if the issue is not solved on vscode side, perhaps we can make the migration tools 'read' the lowercase drive letter.

[darshankawar]

I tried again on Windows 10 using VSCode and Dart 2.16 but have been unable to replicate this issue. The link I access gets opened properly as mentioned in my previous findings: #100134 (comment)

I am going ahead and labeling it for further investigation from the team. Per Reporters, they are seeing this on Windows 11.