Add default values to HelpBuilder output

[NikiforovAll]

Fixes: #619

And output deviates from the initially discussed format in favour of a format that resembles docopt style. Please see the added tests for more details.

[jonsequitur]

Thanks, @NikiforovAll! Aligning to docopt's format makes good sense.

It occurs to me while looking at the code that it would be helpful to have an example of the complete test output. ApprovalTests provides a great way to do this by capturing output into a file that serves as a testable artifact in the repo. Would you mind adding a test using this approach for a single root command help, with a good variety of features in use (give the root command a custom name, options and arguments with and without default values, required and non-required options, and an enum so we can see the values list)?

/cc @KathleenDollard @Keboo

[NikiforovAll]

Yes, sure thing.

[NikiforovAll]

@jonsequitur As I understand, ApprovalTests approach is not used in this repo at the moment. Do you want me to create another issue + PR to add support for ApprovalTests to keep things nice and clean?

[jonsequitur]

Adding commits to the same PR is fine.

[jonsequitur]

This is super helpful.

[NikiforovAll]

I've tried to figure this out, but no luck. It looks like in some cases the content of .approved.txt is empty and in others, the file could not be accessed.

File: Windows_NT_Windows Release - System.CommandLine.Tests_netcoreapp3.1_x64.log

Assert.Equal() Failure � (pos 0) Expected: Actual: the-root-command:\r\n Test description\r\n\r\nъъъ � (pos 0)

File: Linux_Ubuntu 16.04 Debug - System.CommandLine.Tests_netcoreapp3.1_x64.log

System.UnauthorizedAccessException : Access to the path '/_/src/System.CommandLine.Tests/ApprovalTests/Help/Approvals' is denied. --- System.IO.IOException : Permission denied

[jonsequitur]

I haven't seen this kind of issue before. I won't get a chance to dig into it today but a few experiments I would try:

• Put the approvals files in the same directory as the .cs files instead of a subdirectory.
• Add log output for a few file operations (e.g. File.Exists, File.ReadAllText). The exception might be misleading.
• The Assent library is an equivalent library that's based on ApprovalTests but has been .NET Core compatible for longer and I've been using it for a couple years without issues, so maybe try that one instead and see if it's more successful?

Apologies for the complications. I can try these investigations myself in a couple of days if you don't have the time.

Thanks.

[NikiforovAll]

Turns out ApprovalTests.Net doesn't work in the case of deterministic assemblies. So the workaround is <DeterministicSourcePaths>false</DeterministicSourcePaths>. I'm not sure if it' the way to go. LMKWYT

---

StructuredLogViewer query: $property DeterministicSourcePaths under($project System.CommandLIne.Tests)

The thingy that sets MSBuild property.

<PropertyGroup>
    <DeterministicSourcePaths Condition="'$(DeterministicSourcePaths)' == '' and '$(Deterministic)' == 'true' and '$(ContinuousIntegrationBuild)' == 'true'">true</DeterministicSourcePaths>
</PropertyGroup>

[jonsequitur]

Thanks, @NikiforovAll! This is a really nice addition.