[go] encoding/json/v2: add MarshalerTo and UnmarshalerFrom examples

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Michael Pratt (Gerrit)

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Aug 6, 2026, 2:54:18 PM (4 days ago) Aug 6

to Michael Pratt, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, golang...@luci-project-accounts.iam.gserviceaccount.com, Jonathan Amsterdam, Joseph Tsai, Damien Neil, golang-co...@googlegroups.com

Michael Pratt submitted the change with unreviewed changes

Unreviewed changes

5 is the latest approved patch-set.
The change was submitted with unreviewed changes in the following files:

```
The name of the file: src/encoding/json/v2/example_marshaljson_test.go
Insertions: 5, Deletions: 6.

@@ -36,12 +36,11 @@
 	}
 
 	for k := range keys {
-		// It's tempting to to just call
-		// enc.WriteValue(jsontext.Int(k)) here, since we have a
-		// number. Unfortunately that would ignore a global
-		// json.StringifyNumbers option. Going through MarshalEncode is
-		// the safe option, as it ensure we get all of the standard
-		// marshal behavior for the key type.
+		// Call MarshalEncode instead of Write methods on Encoder so
+		// that the "json" package can automatically handle any options
+		// that may be relevant to the representation of k.
+		// In this case, StringifyNumbers may affect whether k is
+		// quoted or not.
 		if err := json.MarshalEncode(enc, k); err != nil {
 			return err
 		}
```

Change information

Commit message:

encoding/json/v2: add MarshalerTo and UnmarshalerFrom examples

MarshalerTo and UnmarshalerFrom are the preferred way to implement
custom marshaling, but don't have any attached examples.

Add examples for a straightforward set type. I like this example because
it is fairly simple, but also encourages users to handle options.

I continue to be undecided about whether a custom type like this should
want to adhere to StringifyNumbers.

For #71497.

Change-Id: Ib8b92b58cb11cfc47ed5537b2d0740a96a6a6964

Reviewed-on: https://go-review.googlesource.com/c/go/+/810321

Reviewed-by: Jonathan Amsterdam <j...@google.com>

LUCI-TryBot-Result: golang...@luci-project-accounts.iam.gserviceaccount.com <golang...@luci-project-accounts.iam.gserviceaccount.com>

Files: