Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

encoding/json: clearer error message for boolean like prefix in invalid json strings #56332

Open
gansvv opened this issue Oct 19, 2022 · 2 comments
Labels
NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone

Comments

@gansvv
Copy link

gansvv commented Oct 19, 2022

What version of Go are you using (go version)?

$ go version
1.19

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
Using go playground. 
https://go.dev/play/p/-AeaDZbeRj1

What did you do?

Json.Unmarshal tries to box a string that starts with a boolean character ('t' or 'f') into a different error compared to a string starting with any other character. This causes the json validation error to be confusing. Can the error be fixed to be similar in both cases (first character invalid) or make the error for attempted boolean parsing to be different ("invalid boolean prefix detected", etc.).

Reproduced here:
https://go.dev/play/p/-AeaDZbeRj1

Code:

package main

import (
	"encoding/json"
	"fmt"
)

func main() {

	// check valid input
	myJsonString := `{"some":"json"}`

	// check invalid input, like boolean start character.
	myJsonString1 := `test`
	myJsonString2 := `random`
	myJsonString3 := `true`
	var s map[string]interface{}
	fmt.Println(json.Unmarshal([]byte(myJsonString), &s))
	fmt.Println(json.Unmarshal([]byte(myJsonString1), &s))
	fmt.Println(json.Unmarshal([]byte(myJsonString2), &s))
	fmt.Println(json.Unmarshal([]byte(myJsonString3), &s))
}

Output:

invalid character 'e' in literal true (expecting 'r')
invalid character 'r' looking for beginning of value
json: cannot unmarshal bool into Go value of type map[string]interface {}

Program exited.

In the above, the error showing "invalid character 'e' in literal true" can be updated to state "invalid literal..." for clarity.

What did you expect to see?

"invalid literal true, error in character 'e'"

What did you see instead?

invalid character 'e' in literal true (expecting 'r')

@dr2chase dr2chase changed the title affected/package: decode.go - Better exception message for boolean like prefix in invalid json strings encoding/json: decode.go - Better exception message for boolean like prefix in invalid json strings Oct 20, 2022
@dr2chase dr2chase added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Oct 20, 2022
@dr2chase
Copy link
Contributor

dr2chase commented Oct 20, 2022

@dsnet @mvdan

@mvdan
Copy link
Member

mvdan commented Oct 27, 2022

I see what you're saying. There's no "true" in the first input, so the error can be a bit confusing.

"invalid literal true, error in character 'e'"

I don't think this error is particularly better, for what it's worth.

All in all, note that the decoder tokenizes one byte at a time. So when it sees a t, it knows it can only be the beginning of true; same for f and false, or " and a quoted string. That's why the error messages are the way they are.

I think we could do better in terms of human-friendly messages, but I can't think of an obviously better choice right now.

@seankhliao seankhliao changed the title encoding/json: decode.go - Better exception message for boolean like prefix in invalid json strings encoding/json: clearer error message for boolean like prefix in invalid json strings Nov 1, 2022
@seankhliao seankhliao added this to the Unplanned milestone Nov 19, 2022
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Projects
None yet
Development

No branches or pull requests

4 participants