improved user-facing error messages to explain the underlying problem

[technosophos]

Signed-off-by: Matt Butcher matt.butcher@microsoft.com

What this PR does / why we need it:

The issue #7747 is a little bit meandering, but at root, the solution is to fix our error messages to be clearer on why a chart load failed. This replaces a terse error message with one that is more easily understood.

I added some tests, and also modified some existing tests.

Special notes for your reviewer:

If applicable:

• this PR contains documentation
• this PR contains unit tests
• this PR has been tested for backwards compatibility

[bridgetkromhout]

This seems clearer, in that you are explicit about the name of the file Helm is expecting to find here. If someone has named their file with another name, that could provide a pointer as to what to fix.

[bacongobbler]

This certainly clarifies the error message better for users of the CLI, and I appreciate the effort to improve the error message for these users.

However, at the point where c.Validate() is called, we've already loaded the chart in memory. Users who consume the SDK may be "loading" a chart from a JSON stream or constructing the chart in some manner that would not utilize a Chart.yaml. Some might even construct a chart by hand like we do in the unit tests. This error message may confuse those users as no Chart.yaml was consumed while loading their chart.

Is there a way we can instead return this error message during LoadFiles instead, before Validate is called? That way we can enforce the validation when a Chart.yaml is not present in an archive/directory.

[technosophos]

@bacongobbler Done.

[bacongobbler]

LGTM!