Fix #2856: resolver receive previous implementation on render

[roneli]

Fix #2856

When implementing the plugin.ResolverImplementer (for example, to make a CRUD method), the original template initialization code will override that code.

This PR gives the resolver implementor the previous method body, so it will be empty if no previous body was created before.

It does break the interface, but I would assume its a minor inconvenience for anyone who uses this interface to update.

I have:

• Added tests covering the bug / feature (see testing)
• Updated any relevant documentation (see docs)

[coveralls]

coverage: 75.824% (-0.04%) from 75.865%
when pulling 7adcefe on roneli:feat-gqlgen-2854-resolver
into 5524a39 on 99designs:master.

[roneli]

Hi @StevenACoffman,

I would actually find this PR useful for my project if possible for us to merge this also?

I can create a config option that by default that keeps the old version that doesn't "regenerate" after first render which will keep the original intention, and when the flag is on then the resolver will always regenerate + get past generation

WDYT?

[StevenACoffman]

Sorry for not responding earlier.

I was sort of confused with some of the description of this PR and in the issue, so I've gone back and collected the original issues and changed the description.

Breaking an interface is not ideal, and breaking compatibility with someone's established usage is even worse.

If there was a config option that would be better.

[tsingsun]

I added a rewriter to solve the interface changed in 17.41. Now I have updated to 17.45, the code generation is the same as before, thank you for your work.

[bagnaram]

Is there an example of the rewriter? We are experiencing this issue in our codebase with schemeas being overwritten.

[tsingsun]

@bagnaram https://github.com/woocoos/knockout-go/tree/5a6b2d2377263aa42d541167038c0a0761102382/codegen/gqlx

hope it helps