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feat: Add native Go 1.23 iterator support for cursor-based pagination #3965

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feat: Add native Go 1.23 iterator support for cursor-based pagination
gmlewis Feb 3, 2026
312307f
Address review feedback
gmlewis Feb 4, 2026
af11dfa
Update README.md
gmlewis Feb 4, 2026
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11 changes: 9 additions & 2 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -328,7 +328,7 @@ Users who have worked with protocol buffers should find this pattern familiar.
### Pagination ###

All requests for resource collections (repos, pull requests, issues, etc.)
support pagination. Pagination options are described in the
support pagination. Pagination options using page numbers are described in the
`github.ListOptions` struct and passed to the list methods directly or as an
embedded type of a more specific list options struct (for example
`github.PullRequestListOptions`). Pages information is available via the
Expand All @@ -355,12 +355,19 @@ for {
}
```

Pagination options using string cursors are described in the `github.ListCursorOptions`
struct and passed to the list methods directly or as an
embedded type of a more specific list cursor options struct (for example
`github.ListGlobalSecurityAdvisoriesOptions`). Similarly, cursor and pages information
is available via the `github.Response` struct.

#### Iterators ####

Go v1.23 introduces the new `iter` package.

The new `github/gen-iterators.go` file auto-generates "*Iter" methods in `github/github-iterators.go`
for all methods that support page number iteration (using the `NextPage` field in each response).
for all methods that support page number iteration (using the `NextPage` field in each response)
or string cursor iteration (using the `Cursor` field in each response).
To handle rate limiting issues, make sure to use a rate-limiting transport.
(See [Rate Limiting](/#rate-limiting) above for more details.)
To use these methods, simply create an iterator and then range over it, for example:
Expand Down
133 changes: 78 additions & 55 deletions github/gen-iterators.go
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Original file line number Diff line number Diff line change
Expand Up @@ -101,24 +101,25 @@ type structDef struct {
}

type method struct {
RecvType string
RecvVar string
ClientField string
MethodName string
IterMethod string
Args string
CallArgs string
TestCallArgs string
ZeroArgs string
ReturnType string
OptsType string
OptsName string
OptsIsPtr bool
UseListOptions bool
UsePage bool
TestJSON1 string
TestJSON2 string
TestJSON3 string
RecvType string
RecvVar string
ClientField string
MethodName string
IterMethod string
Args string
CallArgs string
TestCallArgs string
ZeroArgs string
ReturnType string
OptsType string
OptsName string
OptsIsPtr bool
UseListCursorOptions bool
UseListOptions bool
UsePage bool
TestJSON1 string
TestJSON2 string
TestJSON3 string
}

// customTestJSON maps method names to the JSON response they expect in tests.
Expand Down Expand Up @@ -164,16 +165,24 @@ func (t *templateData) processStructs(f *ast.File) {
}
}

func (t *templateData) hasListCursorOptions(structName string) bool {
return t.hasOptions(structName, "ListCursorOptions")
}

func (t *templateData) hasListOptions(structName string) bool {
return t.hasOptions(structName, "ListOptions")
}

func (t *templateData) hasOptions(structName, optionsType string) bool {
sd, ok := t.Structs[structName]
if !ok {
return false
}
for _, embed := range sd.Embeds {
if embed == "ListOptions" {
if embed == optionsType {
return true
}
if t.hasListOptions(embed) {
if t.hasOptions(embed, optionsType) {
return true
}
}
Expand Down Expand Up @@ -290,11 +299,12 @@ func (t *templateData) processMethods(f *ast.File) error {
continue
}

useListCursorOptions := t.hasListCursorOptions(optsType)
useListOptions := t.hasListOptions(optsType)
usePage := t.hasIntPage(optsType)

if !useListOptions && !usePage {
logf("Skipping %s.%s: opts %s does not have ListOptions or Page int", recvType, fd.Name.Name, optsType)
if !useListCursorOptions && !useListOptions && !usePage {
logf("Skipping %s.%s: opts %s does not have ListCursorOptions, ListOptions, or Page int", recvType, fd.Name.Name, optsType)
continue
}

Expand All @@ -316,24 +326,25 @@ func (t *templateData) processMethods(f *ast.File) error {
testJSON3 := strings.ReplaceAll(testJSON, "[]", "[{},{}]") // Call 2 - return 2 items

m := &method{
RecvType: recType,
RecvVar: recvVar,
ClientField: clientField,
MethodName: fd.Name.Name,
IterMethod: fd.Name.Name + "Iter",
Args: strings.Join(args, ", "),
CallArgs: strings.Join(callArgs, ", "),
TestCallArgs: strings.Join(testCallArgs, ", "),
ZeroArgs: strings.Join(zeroArgs, ", "),
ReturnType: eltType,
OptsType: optsType,
OptsName: optsName,
OptsIsPtr: optsIsPtr,
UseListOptions: useListOptions,
UsePage: usePage,
TestJSON1: testJSON1,
TestJSON2: testJSON2,
TestJSON3: testJSON3,
RecvType: recType,
RecvVar: recvVar,
ClientField: clientField,
MethodName: fd.Name.Name,
IterMethod: fd.Name.Name + "Iter",
Args: strings.Join(args, ", "),
CallArgs: strings.Join(callArgs, ", "),
TestCallArgs: strings.Join(testCallArgs, ", "),
ZeroArgs: strings.Join(zeroArgs, ", "),
ReturnType: eltType,
OptsType: optsType,
OptsName: optsName,
OptsIsPtr: optsIsPtr,
UseListCursorOptions: useListCursorOptions,
UseListOptions: useListOptions,
UsePage: usePage,
TestJSON1: testJSON1,
TestJSON2: testJSON2,
TestJSON3: testJSON3,
}
t.Methods = append(t.Methods, m)
}
Expand Down Expand Up @@ -432,12 +443,26 @@ func ({{.RecvVar}} *{{.RecvType}}) {{.IterMethod}}({{.Args}}) iter.Seq2[{{.Retur
}
}

{{if and .UseListCursorOptions .UseListOptions}}
if resp.Cursor == "" && resp.NextPage == 0 {
break
}
{{.OptsName}}.ListCursorOptions.Cursor = resp.Cursor
{{.OptsName}}.ListOptions.Page = resp.NextPage
{{else if .UseListCursorOptions}}
if resp.Cursor == "" {
break
}
{{.OptsName}}.ListCursorOptions.Cursor = resp.Cursor
{{else if .UseListOptions}}
if resp.NextPage == 0 {
break
}
{{if .UseListOptions}}
{{.OptsName}}.ListOptions.Page = resp.NextPage
{{else}}
if resp.NextPage == 0 {
break
}
{{.OptsName}}.Page = resp.NextPage
{{end -}}
}
Expand All @@ -464,20 +489,23 @@ func Test{{.RecvType}}_{{.IterMethod}}(t *testing.T) {
callNum++
switch callNum {
case 1:
{{- if .UseListCursorOptions}}
w.Header().Set("Link", ` + "`" + `<https://api.github.com/?cursor=yo>; rel="next"` + "`" + `)
{{else}}
w.Header().Set("Link", ` + "`" + `<https://api.github.com/?page=1>; rel="next"` + "`" + `)
fmt.Fprint(w, ` + "`" + `{{.TestJSON1}}` + "`" + `) // Call 1 below: return 3 items, NextPage=1, no errors
{{end -}}
fmt.Fprint(w, ` + "`" + `{{.TestJSON1}}` + "`" + `)
case 2:
fmt.Fprint(w, ` + "`" + `{{.TestJSON2}}` + "`" + `) // still Call 1 below: return 4 more items, no next page, no errors
fmt.Fprint(w, ` + "`" + `{{.TestJSON2}}` + "`" + `)
case 3:
fmt.Fprint(w, ` + "`" + `{{.TestJSON3}}` + "`" + `) // Call 2 below: return 2 items, no next page, no errors
fmt.Fprint(w, ` + "`" + `{{.TestJSON3}}` + "`" + `)
case 4:
w.WriteHeader(http.StatusNotFound) // Call 3 below: endpoint returns an error
w.WriteHeader(http.StatusNotFound)
case 5:
fmt.Fprint(w, ` + "`" + `{{.TestJSON3}}` + "`" + `) // Call 4 below: return 2 items, no next page, no errors
fmt.Fprint(w, ` + "`" + `{{.TestJSON3}}` + "`" + `)
}
})

// Call 1: iterator using zero values
iter := client.{{.ClientField}}.{{.IterMethod}}({{.ZeroArgs}})
var gotItems int
for _, err := range iter {
Expand All @@ -490,10 +518,9 @@ func Test{{.RecvType}}_{{.IterMethod}}(t *testing.T) {
t.Errorf("client.{{.ClientField}}.{{.IterMethod}} call 1 got %v items; want %v", gotItems, want)
}

// Call 2: iterator using non-nil opts
{{.OptsName}} := &{{.OptsType}}{}
iter = client.{{.ClientField}}.{{.IterMethod}}({{.TestCallArgs}})
gotItems = 0 // reset
gotItems = 0
for _, err := range iter {
gotItems++
if err != nil {
Expand All @@ -504,9 +531,8 @@ func Test{{.RecvType}}_{{.IterMethod}}(t *testing.T) {
t.Errorf("client.{{.ClientField}}.{{.IterMethod}} call 2 got %v items; want %v", gotItems, want)
}

// Call 3: iterator returns an error
iter = client.{{.ClientField}}.{{.IterMethod}}({{.ZeroArgs}})
gotItems = 0 // reset
gotItems = 0
for _, err := range iter {
gotItems++
if err == nil {
Expand All @@ -517,16 +543,13 @@ func Test{{.RecvType}}_{{.IterMethod}}(t *testing.T) {
t.Errorf("client.{{.ClientField}}.{{.IterMethod}} call 3 got %v items; want 1 (an error)", gotItems)
}

// Call 4: iterator returns false
iter = client.{{.ClientField}}.{{.IterMethod}}({{.ZeroArgs}})
gotItems = 0 // reset
gotItems = 0
iter(func(item {{.ReturnType}}, err error) bool {
gotItems++
if err != nil {
t.Errorf("Unexpected error: %v", err)
}
// Force the iterator to hit:
// if !yield(item, nil) { return }
return false
})
if gotItems != 1 {
Expand Down
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