[Feature Request]: Types for file paths and plain text

[jrdodds]

Summary

In documentation/specs/proposed, security-metadata.md states:

We envision MSBuild to have a first-class-[citizen] type system for [its] data and tasks. 'Secret' would be one of the data types ...

If a type system is introduced, please include a file path type and a plain text type.

Background and Motivation

When a TaskItem is constructed (or ItemSpec is set), the value is passed through FileUtilities.FixFilePath:

msbuild/src/Utilities/TaskItem.cs

Lines 75 to 81 in 1725b24

	public TaskItem(
	string itemSpec)
	{
	ErrorUtilities.VerifyThrowArgumentNull(itemSpec, nameof(itemSpec));
	_itemSpec = FileUtilities.FixFilePath(itemSpec);
	}

msbuild/src/Utilities/TaskItem.cs

Lines 152 to 163 in 1725b24

	public string ItemSpec
	{
	get => _itemSpec == null ? string.Empty : EscapingUtilities.UnescapeAll(_itemSpec);
	set
	{
	ErrorUtilities.VerifyThrowArgumentNull(value, nameof(ItemSpec));
	_itemSpec = FileUtilities.FixFilePath(value);
	_fullPath = null;
	}
	}

msbuild/src/Shared/FileUtilities.cs

Lines 543 to 546 in 1725b24

	internal static string FixFilePath(string path)
	{
	return string.IsNullOrEmpty(path) || Path.DirectorySeparatorChar == '\\' ? path : path.Replace('\\', '/'); // .Replace("//", "/");
	}

FixFilePath makes no change under Windows (where Path.DirectorySeparatorChar will be '\\') but on *NIX OSs (macOS and Linux) a \ character will be replaced with a / character. This makes some sense for file paths but when an Item collection is used for data that is not file paths and that contains \ characters, the data is corrupted.

This issue shows up in multiple places and ways but one example is using the ReadLinesFromFile task to read a JavaScript file that has code using regular expressions. The \ character is an escape character in REs. The same MSBuild project will work correctly on Windows and corrupt the RE expressions on Linux and macOS.

Proposed Feature

• Have a plain text type for values that should not be interpreted.
• Have a file path type that supports making file paths portable/convertible.
  • Can be defined with a relative path in either a Windows style or a UNIX style and, when its value is accessed, it tries to default to the current platform.
  • It should be possible to explicitly get a UNIX style path under Windows and vice versa.
  • Converting fully qualified paths may not be supported.

Alternative Designs

No response

[jrdodds]

See bugs #1622 and #3468.

[JanKrivanek]

FYI @baronfel

Thank you @jrdodds for a nice suggestion.
The strong type system is not yet on the top of MSBuild team priority list (though it's something that was discussed internaly couple times).

[lonix1]

SO question issue that started this issue.