The testable example "ExamplePrivateHandle" is incorrectly passing

[ameowlia]

👋 Hello,

I am investigating the golang issue: golang/go#48362, where testable examples are causing false positives when the output comment block is not the last comment block example.

I ran a parser against the top golang repos, including this repo and I found this bug with your ExamplePrivateHandle testable example.

If you combine the comment blocks to test as intended (see below) your test fails because the id is not 1234 like the output expects.

This is the code I suspect that you intended:

func ExamplePrivateHandle() {
	dns.PrivateHandle("APAIR", TypeAPAIR, NewAPAIR)
	defer dns.PrivateHandleRemove(TypeAPAIR)

	rr, err := dns.NewRR("miek.nl. APAIR (1.2.3.4    1.2.3.5)")
	if err != nil {
		log.Fatal("could not parse APAIR record: ", err)
	}
	fmt.Println(rr)

	m := new(dns.Msg)
	m.Id = 12345
	m.SetQuestion("miek.nl.", TypeAPAIR)
	m.Answer = append(m.Answer, rr)

	fmt.Println(m)
	
	// Output: miek.nl.	3600	IN	APAIR	1.2.3.4 1.2.3.5
	// ;; opcode: QUERY, status: NOERROR, id: 12345
	// ;; flags: rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
	//
	// ;; QUESTION SECTION:
	// ;miek.nl.	IN	 APAIR
	//
	// ;; ANSWER SECTION:
	// miek.nl.	3600	IN	APAIR	1.2.3.4 1.2.3.5
}

This fails with:

$ go test ./...
--- FAIL: ExamplePrivateHandle (0.00s)
got:
miek.nl.        3600    IN      APAIR   1.2.3.4 1.2.3.5
;; opcode: QUERY, status: NOERROR, id: 49593
;; flags: rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;miek.nl.       IN       APAIR

;; ANSWER SECTION:
miek.nl.        3600    IN      APAIR   1.2.3.4 1.2.3.5
want:
miek.nl.        3600    IN      APAIR   1.2.3.4 1.2.3.5
;; opcode: QUERY, status: NOERROR, id: 12345
;; flags: rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;miek.nl.       IN       APAIR

;; ANSWER SECTION:
miek.nl.        3600    IN      APAIR   1.2.3.4 1.2.3.5
FAIL
FAIL    github.com/miekg/dns    2.974s
ok      github.com/miekg/dns/dnsutil    (cached)
FAIL

[tmthrgd]

Thanks! I've never been a huge fan of how Go did Example testing and clearly it can be quite britle.

Would you care to open a PR and fix it? If not, let me know and I'll be happy to.

[ameowlia]

This isn't simple "just move one comment" case. In this case the id changes every time you run this code. I'll let you handle this PR @tmthrgd 😄

[miekg]

You can provide a function that returns an ID that is static for this test.

…

On Thu, 18 Nov 2021, 22:09 Amelia Downs, ***@***.***> wrote: This isn't simple "just move one comment" case. In this case the id changes every time you run this code. I'll let you handle this PR @tmthrgd <https://github.com/tmthrgd> 😄 — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1299 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AACWIW45DIV4YLTXCJMO4ADUMVTPHANCNFSM5EPA5NIQ> .

[miekg]

Fixed via #1354