fix: add modifying nested struct diagnostic

[TimothyMakkison]

Add diagnostic for modifying a temporary value type

Description

Added check for if a nested value type is being modified.

Probably not a common issue so I went with a diagnostic.
I considered nested chain assignment or a with expression ie target.NestedValue = target.NestedValue with { StringValue = src.StringValue }; (can repeatedly chain)

Fixes #516

Checklist

• The existing code style is followed
• The commit message follows our guidelines
• Performed a self-review of my code
• Hard-to-understand areas of my code are commented
• The documentation is updated (as applicable)
• Unit tests are added/updated
• Integration tests are added/updated (as applicable, especially if feature/bug depends on roslyn or framework version in use)

[codecov]

Codecov Report

Merging #551 (c15c130) into main (3ee2e96) will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #551      +/-   ##
==========================================
+ Coverage   90.89%   90.94%   +0.05%     
==========================================
  Files         172      172              
  Lines        6106     6141      +35     
  Branches      777      782       +5     
==========================================
+ Hits         5550     5585      +35     
  Misses        378      378              
  Partials      178      178              

Files Changed	Coverage Δ
...pingBodyBuilders/ObjectMemberMappingBodyBuilder.cs	100.00% <100.00%> (ø)
...Riok.Mapperly/Diagnostics/DiagnosticDescriptors.cs	100.00% <100.00%> (ø)

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[TimothyMakkison]

Sorry, I though I had fixed all of this a week ago. Turns out I forgot to push it 😅

• fixed indentation
• use correct bool
• update test to verify mapping is not generated
• use indexer instead of linq
• added support for struct fields

This only checks the second last item, but couldn't be any in the path except for the last item be a problem?

Yeah, I'm still not sure about this. I decided that the only the last two values mattered.. Even if all the preceeding members are structs, the error only occurs when trying to set the final struct property. If the penultimate member is a class the error won't occur.

Cone to think of it, this probably isn't true when accessing fields

[latonz]

@TimothyMakkison ah yep on a second thought I think that makes sense, that only the second last is checked.

[TimothyMakkison]

Added CS1612 to error message.

Modified the check to iterate backwards, checking for value type properties. Checking the penultimate member would work if field types didn't exist

[TimothyMakkison]

Analyzer doesn't like the length of ValidateMappingSpecification. I've extracted the struct method but it's still too long.
Might be a bit controversial but I've temporarily disabled the warning. I'd argue a a long method with simple checks is easier to understand than one method calling 6 simple methods. Especially when the bulk of the length are arguments placed on new lines.
WDYT?

[latonz]

IMO its okay here to ignore the warning, could you change it to suppressmessage attribute? Often the readability is improved that when reading a method and submethods are called instead of inlined code, code which I'm not interested in reading can be skipped easier.

[TimothyMakkison]

IMO its okay here to ignore the warning, could you change it to suppressmessage attribute?

Added attribute

Often the readability is improved that when reading a method and submethods are called instead of inlined code, code which I'm not interested in reading can be skipped easier.

Should I extract all the methods?

[latonz]

Nope, should be fine like this, just my general opinion on the topic…

[github-actions]

🎉 This PR is included in version 3.1.0-next.2 🎉

The release is available on:

• GitHub release
• v3.1.0-next.2

Your semantic-release bot 📦🚀

[github-actions]

🎉 This PR is included in version 3.1.0 🎉

The release is available on:

• GitHub release
• v3.1.0

Your semantic-release bot 📦🚀