Fix "new Flutter Version" error on FlutterRun

[obemu]

About

This PR implements a fix for #473.

Problem

The first time a user executes any command or sub-command of the flutter CLI tool, they are greeted with the Welcome to Flutter! banner and if their Flutter SDK is not up-to-date, or if it has been a while since the last time they executed any command, they are also greeted with the New Flutter Version banner. Both may be displayed at the same time.

These banners are always printed to STDOUT, if the conditions explained above are met, including running the Flutter debug adapter (flutter debug_adapter), which is executed when running the command FlutterRun. This interferes with nvim-daps ability to parse JsonRPC messages, which in turn causes the internal parser loop of nvim-dap to crash, resulting in this error:

.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:97: .../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:30: Content-Length not found in headers: 
┌─────────────────────────────────────────────────────────┐
│ A new version of Flutter is available!                  │
│                                                         │
│ To update to the latest version, run "flutter upgrade". │
└─────────────────────────────────────────────────────────┘

  ╔════════════════════════════════════════════════════════════════════════════╗
  ║                 Welcome to Flutter! - https://flutter.dev                  ║
  ║                                                                            ║
  ║ The Flutter tool uses Google Analytics to anonymously report feature usage ║
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Content-Length: 584
Content-Type: application/vscode-jsonrpc; charset=utf-8

stack traceback:
	[C]: in function 'parse_chunk'
	.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:97: in function <.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:85>
Error executing callback:
.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:97: cannot resume dead coroutine
stack traceback:
	[C]: in function 'parse_chunk'
	.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:97: in function <.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:85>
Error executing callback:
.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:97: cannot resume dead coroutine
stack traceback:
	[C]: in function 'parse_chunk'
	.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:97: in function <.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:85>
Error executing callback:
.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:97: cannot resume dead coroutine
stack traceback:
	[C]: in function 'parse_chunk'
	.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:97: in function <.../.local/share/nvim/plugged/nvim-dap/lua/dap/rpc.lua:85>

Fix

My Solution

As I can't modify the code of the nvim-dap plugin to ignore these banners, I needed to prevent them from showing up. This has been implemented with the banner.lua module. This new module exposes two public functions:

• clear_startup_banners(...) and
• reset_cache()

Executing clear_startup_banners(...) executes the flutter CLI tool in the background and detects any banners, after the command is done the API user receives table with flags set for each banner. This method is used in commands.lua, before the DebugRunner:run or JobRunner:run method gets executed, which allows this plugin to inform the user of a new Flutter SDK version and the Runner to execute without triggering any errors.

Another possible Solution

To create a custom script for each platform (Windows and Unix) that executes the flutter debug_adapter command and detects any banners. The scripts would then be used to register a debug adapter in nvim-dap, for example:

    ...
    dap.adapters.dart = {
      type = "executable",
      command = is_windows and custom_flutter_dap.bat or custom_flutter_dap.sh
      args = { },
    }
    ...

NOTE: I haven't tested this second solution, it is just something I thought of.

Testing

You can manually trigger the banners to be shown again by deleting certain files.

• Delete $FLUTTER_SDK/bin/cache/flutter_version_check.stamp for the New Flutter Version banner.
• Delete $HOME/.config/flutter/tool_state for the Welcome to Flutter banner.

[obemu]

@sidlatau How are we looking, do I need to change anything to get this merged?

[sidlatau]

Nice work, @obemu! Thank you for providing information how to trigger these banners, I tested it, works as expected.