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gmlewis merged 3 commits into from
Feb 4, 2026
+1,573 −2,224
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feat: Add native Go 1.23 iterator support for cursor-based pagination #3965

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378c150
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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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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