Caching SVG doesn't cache CSS class name and Viewbox settings

[drpeck]

There is an issue where caching an SVG with a class name (or Viewbox setting) causes the class name to be contained in the cache. If outputting the same SVG later includes the class name from the first usage.

This PR splits the caching so that the file read is independently cached from the Css class name and Viewbox settings.

[drpeck]

Honestly, I'm pretty confident about this PR but it shouldn't be merged yet. I'm not sure how best to test it. The unit tests all pass but I failed to create new unit tests as I couldn't work out how to mock the AppCache correctly. Any ideas how to do this? Do you also have an existing method of testing this on a 'real' site, or should I work something out for that?

[Copilot]

Pull Request Overview

This PR fixes a caching bug where SVG content was cached with CSS classes and ViewBox settings, causing subsequent renders of the same SVG to incorrectly inherit attributes from previous usages. The solution separates the caching of file contents from attribute processing.

• Splits SVG caching into two levels: raw file content and processed content with attributes
• Extracts cache key calculation and configuration fetching into separate methods
• Refactors attribute processing into a dedicated method for better separation of concerns

Comments suppressed due to low confidence (1)

Our.Umbraco.TagHelpers/InlineSvgTagHelper.cs:244

• [nitpick] The method name 'ParseAndSetAttrs' uses an abbreviation. Consider renaming to 'ParseAndSetAttributes' for better readability and consistency with the rest of the codebase.

        private string ParseAndSetAttrs (string cleanedFileContents) {

[Copilot]

Using GetHashCode() for cache keys can cause collisions since GetHashCode() is not guaranteed to be unique or consistent across application restarts. Consider using a more deterministic approach like combining the actual values or using a cryptographic hash.

Suggested change

	=> $"SvgWithAttributes ({CssClass?.GetHashCode()}_{cleanedFileContents.GetHashCode()})";
	{
	// Use actual values or a deterministic hash for the cache key
	var cssClassValue = CssClass ?? string.Empty;
	var combined = cssClassValue + "|" + cleanedFileContents;
	var hash = ComputeSHA256Hash(combined);
	return $"SvgWithAttributes ({hash})";
	}
	private static string ComputeSHA256Hash(string input)
	{
	using (var sha256 = SHA256.Create())
	{
	var bytes = Encoding.UTF8.GetBytes(input);
	var hashBytes = sha256.ComputeHash(bytes);
	var sb = new StringBuilder();
	foreach (var b in hashBytes)
	{
	sb.Append(b.ToString("x2"));
	}
	return sb.ToString();
	}
	}