feat(gengapic): generate helpers for Go 1.23 iterators

This changes starts generating build tag protected adapters for
using our iterator types in Go range expressions.

Related: googleapis/gax-go#358

internal/gengapic/auxiliary.go

@@ -79,6 +79,10 @@ func (g *generator) genAuxFile() error {
  g.commit(filepath.Join(g.opts.outDir, "auxiliary.go"), g.opts.pkgName)
  g.reset()
 
+ g.genIteratorsGo123()
+ g.commitWithBuildTag(filepath.Join(g.opts.outDir, "auxiliary_go123.go"), g.opts.pkgName, "go1.23")
+ g.reset()
+
  return nil
 }
 
@@ -123,6 +127,17 @@ func (g *generator) genIterators() error {
  return nil
 }
 
+// genIteratorsGo123 generates adapters for Go iterators for Go versions 1.23+.
+func (g *generator) genIteratorsGo123() {
+ // Sort iterators to generate by type name to
+ // avoid spurious regenerations created by
+ // non-deterministic map traversal order.
+ iters := sortIteratorMap(g.aux.iters)
+ for _, iter := range iters {
+ g.pagingIterGo123(iter)
+ }
+}
+
 // sortIteratorMap sorts the map of iterator types by iterTypeName.
 func sortIteratorMap(m map[string]*iterType) []*iterType {
  var iters []*iterType

internal/gengapic/auxiliary_test.go

@@ -444,6 +444,22 @@ func TestGenIterators(t *testing.T) {
  }
 
  txtdiff.Diff(t, g.pt.String(), filepath.Join("testdata", "gen_iterators.want"))
+
+ g.reset()
+
+ wantImports = map[pbinfo.ImportSpec]bool{
+ {Path: "iter"}: true,
+ {Path: "github.com/googleapis/gax-go/v2/iterator"}: true,
+ {Name: "examplepb", Path: "cloud.google.com/go/example/apiv1/examplepb"}: true,
+ }
+
+ g.genIteratorsGo123()
+
+ if diff := cmp.Diff(g.imports, wantImports); diff != "" {
+ t.Errorf("imports got(-),want(+):\n%s", diff)
+ }
+
+ txtdiff.Diff(t, g.pt.String(), filepath.Join("testdata", "gen_iterators_go123.want"))
 }
 
 func TestSortOperationWrapperMap(t *testing.T) {

internal/gengapic/generator.go

@@ -221,12 +221,19 @@ func (g *generator) printf(s string, a ...interface{}) {
 
 // TODO(chrisdsmith): Add generator_test.go with TestCommit
 
+func (g *generator) commit(fileName, pkgName string) int {
+ return g.commitWithBuildTag(fileName, pkgName, "")
+}
+
 // commit adds header, etc to current pt and returns the line length of the
 // final file output.
-func (g *generator) commit(fileName, pkgName string) int {
+func (g *generator) commitWithBuildTag(fileName, pkgName, buildTag string) int {
  var header strings.Builder
  fmt.Fprintf(&header, license.Apache, time.Now().Year())
  header.WriteString(g.headerComments.String() + "\n")
+ if buildTag != "" {
+ fmt.Fprintf(&header, "//go:build %s\n\n", buildTag)
+ }
  fmt.Fprintf(&header, "package %s\n\n", pkgName)
 
  var imps []pbinfo.ImportSpec

internal/gengapic/paging.go

@@ -389,3 +389,20 @@ func (g *generator) pagingIter(pt *iterType) {
  g.imports[spec] = true
  }
 }
+
+func (g *generator) pagingIterGo123(pt *iterType) {
+ p := g.printf
+
+ p("// All returns an iterator. If an error is returned by the iterator, the")
+ p("// iterator will stop after that iteration.")
+ p("func (it *%s) All() iter.Seq2[%s, error] {", pt.iterTypeName, pt.elemTypeName)
+ p(" return iterator.RangeAdapter[%s](it.Next)", pt.elemTypeName)
+ p("}")
+ p("")
+
+ g.imports[pbinfo.ImportSpec{Path: "iter"}] = true
+ g.imports[pbinfo.ImportSpec{Path: "github.com/googleapis/gax-go/v2/iterator"}] = true
+ for _, spec := range pt.elemImports {
+ g.imports[spec] = true
+ }
+}

internal/gengapic/testdata/gen_iterators_go123.want

@@ -0,0 +1,6 @@
+// All returns an iterator. If an error is returned by the iterator, the
+// iterator will stop after that iteration.
+func (it *FooIterator) All() iter.Seq2[*examplepb.Foo, error] {
+ return iterator.RangeAdapter[*examplepb.Foo](it.Next)
+}
+