20200213_choria_config_blog

gen.go

// reads config.go and includes parsing of comments
d, err := parser.ParseFile(token.NewFileSet(), "config.go", nil, parser.ParseComments)
panicIfErr(err)

ast.Inspect(d, func(n ast.Node) bool {
    // this function filters and parses the ast, return false to stop descending into a
    // branch of the AST, so we skip over everything till we reach Config struct

    switch t := n.(type) {
    case *ast.TypeSpec:
        // once we reach our Config structure keep going deeper, else skip over
        return t.Name.Name == "Config"
    case *ast.StructType:
        // every field in Config
        for _, field := range t.Fields.List {
            tag := ""
            doc := ""

            // get the tag and clean it up a bit, we need to only touch "confkeys" not other stuff
            if field.Tag != nil && field.Tag.Kind == token.STRING {
            	tag = strings.TrimRight(strings.TrimLeft(field.Tag.Value, "`"), "`")
            }

            // extract the comments
            switch {
            case len(strings.TrimSpace(field.Doc.Text())) > 0:   // comments above the field
                doc = field.Doc.Text()
            
            case len(strings.TrimSpace(field.Comment.Text())) > 0:  // comments after the field like in "Servers"
                doc = field.Comment.Text()
            }

            if strings.Contains(tag, "confkey") && doc != "" {
                // process the doc and generate the above docStrings
            }
        }
    }

    return true
})