extension_discovery: add findPackageConfig()

[sigurdm]

This will make it easier to use from a pub workspace.

[github-actions]

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Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
extension_discovery	Non-Breaking	2.0.1-wip	2.0.1-wip	2.0.1-wip	✔️

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File	Coverage
pkgs/extension_discovery/lib/extension_discovery.dart	💚 81 %
pkgs/extension_discovery/lib/src/package_config.dart	💚 78 %

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// Copyright (c) 2024, the Dart project authors. Please see the AUTHORS file
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Package publish validation ✔️

Package	Version	Status
package:cli_config	0.2.1-wip	WIP (no publish necessary)
package:coverage	1.9.2	already published at pub.dev
package:extension_discovery	2.0.1-wip	WIP (no publish necessary)
package:graphs	2.3.3-wip	WIP (no publish necessary)
package:mime	2.0.0-wip	WIP (no publish necessary)
package:oauth2	2.0.4-wip	WIP (no publish necessary)
package:source_map_stack_trace	2.1.3-wip	WIP (no publish necessary)
package:unified_analytics	6.1.4-wip	WIP (no publish necessary)

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[jonasfj]

Suggested change

	/// package_config will be searched by looking in all parent directories.
	/// [packageConfig] will be searched by looking in all parent directories.

[kenzieschmoll]

this logic is assuming / is the separator, which won't be true for Windows. Should we be using the path package instead to support Windows paths?

CC @DanTup since you have resolved many windows path issues in the past.

[sigurdm]

Good point - I think we are good here though.

These are file urls not file paths. Urls always use / as a separator.

Eg. this program:

import 'dart:io';

void main(List<String> args) {
  print(Uri.file('c:\\abc\\def\\', windows: true));
}

Prints:

file:///c:/abc/def/

[DanTup]

Yep, this looks reasonable to me.

The things that usually cause issues are reading .path from a File URI, assuming it's correct for Windows (it's not, but it is correct for non-Windows), and going to/from Windows paths when running in the browser (because Dart always treats web as non-Windows even if the file:/// URI is a Windows path).

I note the code below is doing File.fromUri() which will call toFilePath() but since it's calling existsSync() I assume that this code only runs on the host machine (not in a browser) and therefore I don't think any of those gotchas apply here.

[sigurdm]

I assume that this code only runs on the host machine (not in a browser)

Yes, this is running on the host.