redo comment parsing to set up for field-level config

generate/comments.go

@@ -0,0 +1,47 @@
+package generate
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/vektah/gqlparser/v2/ast"
+	"github.com/vektah/gqlparser/v2/parser"
+)
+
+func (g *generator) parsePrecedingComment(pos *ast.Position) (comment string, directives []*ast.Directive, err error) {
+	var commentLines []string
+	sourceLines := strings.Split(pos.Src.Input, "\n")
+	for i := pos.Line - 1; i > 0; i-- {
+		line := strings.TrimSpace(sourceLines[i-1])
+		trimmed := strings.TrimSpace(strings.TrimPrefix(line, "#"))
+		if strings.HasPrefix(line, "# @genqlient") {
+			directive, err := parseDirective(trimmed, pos)
+			if err != nil {
+				return "", nil, err
+			}
+			directives = append(directives, directive)
+		} else if strings.HasPrefix(line, "#") {
+			commentLines = append(commentLines, trimmed)
+		} else {
+			break
+		}
+	}
+
+	reverse(commentLines)
+
+	return strings.TrimSpace(strings.Join(commentLines, "\n")), directives, nil
+}
+
+func parseDirective(line string, pos *ast.Position) (*ast.Directive, error) {
+	// HACK: parse the "directive" by making a fake query containing it.
+	fakeQuery := fmt.Sprintf("query %v { field }", line)
+	doc, err := parser.ParseQuery(&ast.Source{
+		Name: fmt.Sprintf("@genqlient directive at %v:%v:%v",
+			pos.Src.Name, pos.Line, pos.Column),
+		Input: fakeQuery,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return doc.Operations[0].Directives[0], nil
+}