[rewrite for single-file] add a new flag for enable_rewrite_for_single_file vs. single-file mode overwrites the existing resolver.go but build time breaking experience?

[hailyngx]

What happened?

I wanted to use the rewrite for single-file mode and made direct changes to generateSingleFile. I made changes in very similar fashion to generatePerSchema so it behaved similarly in terms of rewriting the file. However, when I run go generate at the root of gqlgen folder. One of the folder insider _examples broke, specifically type-system-extension.

What did you expect?

I understand that the current generateSingleFile does not support rewriting in single-file mode. Still, I want to integrate resolvergen to a build system that cannot work with generatePerSchema but maintaining the rewrite function is important for large schema changes.

Potential Solution

Can we add a new flag enable_rewrite_for_single_file and build on top of that? By doing so, we will not break any build from the _examples while allowing for some flexibility in using single-file. The default for this flag is false but we can use it by adding to our config file:

resolver:
  filename: resolver/resolver.go
  enable_rewrite_for_single_file: true

Potential Implementation

codegen/config/resolver.go

• Add a new boolean field EnableRewriteForSingleFile inside ResolverConfig struct.

plugin/resolvergen/resolver.go

• Add a new generateSingleFileEnableRewrite function with similar rewrite behaviors to generatePerSchema
• Inside GenerateCode

func (m *Plugin) GenerateCode(data *codegen.Data) error {
 	switch data.Config.Resolver.Layout {
 	case config.LayoutSingleFile:
		if data.Config.Resolver.EnableRewriteForSingleFile { // add a conditional statement to use rewrite for single-file
			return m.generateSingleFileEnableRewrite(data)
	}
 		return m.generateSingleFile(data)
 	case config.LayoutFollowSchema:
 		return m.generatePerSchema(data)

• Change file notice: // THIS CODE WILL BE UPDATED WITH SCHEMA CHANGES. PREVIOUS IMPLEMENTATION FOR SCHEMA CHANGES WILL BE KEPT IN THE COMMENT SECTION. IMPLEMENTATION FOR UNCHANGED SCHEMA WILL BE KEPT.
• Added unit test and testdata to cover the new function GenerateSingleFileEnableRewrite.

Would appreciate any input! 💡 Thank you for your time.

[StevenACoffman]

See #3243