panic while printing panic value: type gojq.Operator

[ceving]

I would like to dump jq.Query:

package main

import (
	"fmt"
	"log"
	jq "github.com/itchyny/gojq"
	"os"
)

func ReadJsonQueryFile(fname string) (*jq.Query, error) {
	data, err := os.ReadFile(fname)
	if err != nil {
		return nil, fmt.Errorf("Can not read JSON query file %q", fname, err)
	}
	query, err := jq.Parse(string(data))
	if err != nil {
		return nil, fmt.Errorf("Can not parse JSON query file %q", fname, err)
	}
	return query, nil
}

func DumpQuery(q *jq.Query) {
	fmt.Printf("Meta: %+v\n", q.Meta)
	fmt.Printf("Imports: %+v\n", q.Imports)
	fmt.Printf("FuncDefs: %+v\n", q.FuncDefs)
	fmt.Printf("Term: %+v\n", q.Term)
	fmt.Printf("Left: %+v\n", q.Left)
	fmt.Printf("Op: %+v\n", q.Op)
	fmt.Printf("Right: %+v\n", q.Right)
	fmt.Printf("Func: %+v\n", q.Func)
}

func main() {
	q, err := ReadJsonQueryFile(os.Args[1])
	if err != nil {
		log.Fatal(err)
	}
	DumpQuery(q)
}

When I run the code, it panics:

$ go1.24.0 run jqv.go <(echo '$var')
Meta: <nil>
Imports: []
FuncDefs: []
Term: $var
Left: <nil>
fatal error: panic while printing panic value: type gojq.Operator

I think it should not do that.

[itchyny]

An undocumented assumption that user who is trying to traverse gojq.Query should know is that q.Term and q.{Left, Op, Right} are exclusive, and if q.Term is not nil, you shouldn't access the others. And zero value of Operator is not implemented because this will never be printed under this assumption. Even I don't know how to print the zero value of Operator. How do you expect it to be printed? If you still want to debug the Query struct value, use %#v formatter. gojq.Operator implements fmt.GoStringer interface because printing the struct with Go syntax format is sometimes useful for debugging.