Replace channel-based iterators with new-style ones (#3272)

* Convert functions to iterators

* Change things to use it

* Convert this too

* lint

src/build/build_step.go

@@ -596,8 +596,8 @@ func prepareDirectory(directory string, remove bool) error {
 
 // Symlinks the source files of this rule into its temp directory.
 func prepareSources(state *core.BuildState, graph *core.BuildGraph, target *core.BuildTarget) error {
-	for source := range core.IterSources(state, graph, target, false) {
-		if err := core.PrepareSourcePair(source); err != nil {
+	for src, tmp := range core.IterSources(state, graph, target, false) {
+		if err := core.PrepareSource(src, tmp); err != nil {
 			return err
 		}
 	}

src/build/incrementality.go

@@ -111,13 +111,13 @@ func mustSourceHash(state *core.BuildState, target *core.BuildTarget) []byte {
 // Calculate the hash of all sources of this rule
 func sourceHash(state *core.BuildState, target *core.BuildTarget) ([]byte, error) {
 	h := sha1.New()
-	for source := range core.IterSources(state, state.Graph, target, false) {
-		result, err := state.PathHasher.Hash(source.Src, false, true, false)
+	for src := range core.IterSources(state, state.Graph, target, false) {
+		result, err := state.PathHasher.Hash(src, false, true, false)
 		if err != nil {
 			return nil, err
 		}
 		h.Write(result)
-		h.Write([]byte(source.Src))
+		h.Write([]byte(src))
 	}
 	for _, tool := range target.AllTools() {
 		for _, path := range tool.FullPaths(state.Graph) {
@@ -440,8 +440,8 @@ func RuntimeHash(state *core.BuildState, target *core.BuildTarget, testRun int)
 	hash := append(RuleHash(state, target, true, false), RuleHash(state, target, true, true)...)
 	hash = append(hash, state.Hashes.Config...)
 	h := sha1.New()
-	for source := range core.IterRuntimeFiles(state.Graph, target, true, target.TestDir(testRun)) {
-		result, err := state.PathHasher.Hash(source.Src, false, true, false)
+	for src := range core.IterRuntimeFiles(state.Graph, target, true, target.TestDir(testRun)) {
+		result, err := state.PathHasher.Hash(src, false, true, false)
 		if err != nil {
 			return result, err
 		}
@@ -465,7 +465,7 @@ func PrintHashes(state *core.BuildState, target *core.BuildTarget) {
 	// Note that the logic here mimics sourceHash, but I don't want to pollute that with
 	// optional printing nonsense since it's on our hot path.
 	for source := range core.IterSources(state, state.Graph, target, false) {
-		fmt.Printf("  Source: %s: %s\n", source.Src, b64(state.PathHasher.MustHash(source.Src, target.HashLastModified())))
+		fmt.Printf("  Source: %s: %s\n", source, b64(state.PathHasher.MustHash(source, target.HashLastModified())))
 	}
 	for _, tool := range target.AllTools() {
 		if label, ok := tool.Label(); ok {

src/core/state.go

@@ -9,6 +9,7 @@ import (
 	"hash/crc64"
 	"io"
 	iofs "io/fs"
+	"iter"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -1329,23 +1330,26 @@ func (state *BuildState) DownloadAllInputs(target *BuildTarget, targetDir string
 	return state.RemoteClient.DownloadInputs(target, targetDir, isTest)
 }
 
-// IterInputs returns a channel that iterates all the input files needed for a target.
-func (state *BuildState) IterInputs(target *BuildTarget, test bool) <-chan BuildInput {
+// IterInputs returns a an iterator over all the input files needed for a target.
+func (state *BuildState) IterInputs(target *BuildTarget, test bool) iter.Seq[BuildInput] {
 	if !test {
 		return IterInputs(state, state.Graph, target, true, target.IsFilegroup)
 	}
-	ch := make(chan BuildInput)
-	go func() {
-		ch <- target.Label
+	return func(yield func(BuildInput) bool) {
+		if !yield(target.Label) {
+			return
+		}
 		for _, datum := range target.AllData() {
-			ch <- datum
+			if !yield(datum) {
+				return
+			}
 		}
-		for _, datum := range target.AllTestTools() {
-			ch <- datum
+		for _, tool := range target.AllTestTools() {
+			if !yield(tool) {
+				return
+			}
 		}
-		close(ch)
-	}()
-	return ch
+	}
 }
 
 // DisableXattrs disables xattr support for this build. This is done for filesystems that