Parsing AST in go

ast_parsing.go

package schemagen

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"strings"
)

// getStructsWithBuildTag retrieves all the structs in a Go source file that have a doc string containing a certain build tag.
func GetStructsWithBuildTag(filename, buildTag string) ([]string, error) {
	var result []string

	// Parse the file and generate an AST
	fset := token.NewFileSet()
	node, err := parser.ParseFile(fset, filename, nil, parser.AllErrors|parser.ParseComments)
	if err != nil {
		return nil, err
	}

	// Iterate through all the declarations in the file
	for _, decl := range node.Decls {
		// Check if the declaration is a type declaration
		if genDecl, ok := decl.(*ast.GenDecl); ok && genDecl.Tok == token.TYPE {
			// Doc comment on type declaration
			var typeMatchesTag = strings.Contains(genDecl.Doc.Text(), buildTag)

			// Iterate through all the specs in the type declaration
			for _, spec := range genDecl.Specs {
				if typeSpec, ok := spec.(*ast.TypeSpec); ok {
					// Check if the type is a struct and has a doc string containing the build tag
					if stype, ok := typeSpec.Type.(*ast.StructType); ok {
						// Print struct fields
						for _, field := range stype.Fields.List {
							if i, ok := field.Type.(*ast.Ident); ok {
								fieldType := i.Name

								for _, name := range field.Names {
									fmt.Printf("\tField: name=%s type=%s\n", name.Name, fieldType)
								}
							}
						}

						if typeMatchesTag {
							result = append(result, typeSpec.Name.Name)
							continue
						}

						// type on struct name
						if typeSpec.Doc != nil && strings.Contains(typeSpec.Doc.Text(), buildTag) {
							result = append(result, typeSpec.Name.Name)

						}

					}
				}
			}
		}
	}

	return result, nil
}

/*
print struct field
structType := typeSpec.Type.(*ast.StructType)
for _, field := range structType.Fields.List {
	i := field.Type.(*ast.Ident)
	fieldType := i.Name

	for _, name := range field.Names {
		fmt.Printf("\tField: name=%s type=%s\n", name.Name, fieldType)
	}

}

*/