2 files changed, 442 insertions, 0 deletions
diff --git a/cli/internal/globwatcher/globwatcher.go b/cli/internal/globwatcher/globwatcher.go
new file mode 100644
index 0000000..9226cfa
--- /dev/null
+++ b/cli/internal/globwatcher/globwatcher.go
@@ -0,0 +1,210 @@
+package globwatcher
+
+import (
+	"errors"
+	"fmt"
+	"path/filepath"
+	"sync"
+
+	"github.com/hashicorp/go-hclog"
+	"github.com/vercel/turbo/cli/internal/doublestar"
+	"github.com/vercel/turbo/cli/internal/filewatcher"
+	"github.com/vercel/turbo/cli/internal/fs"
+	"github.com/vercel/turbo/cli/internal/turbopath"
+	"github.com/vercel/turbo/cli/internal/util"
+)
+
+// ErrClosed is returned when attempting to get changed globs after glob watching has closed
+var ErrClosed = errors.New("glob watching is closed")
+
+type globs struct {
+	Inclusions util.Set
+	Exclusions util.Set
+}
+
+// GlobWatcher is used to track unchanged globs by hash. Once a glob registers a file change
+// it is no longer tracked until a new hash requests it. Once all globs for a particular hash
+// have changed, that hash is no longer tracked.
+type GlobWatcher struct {
+	logger       hclog.Logger
+	repoRoot     turbopath.AbsoluteSystemPath
+	cookieWaiter filewatcher.CookieWaiter
+
+	mu         sync.RWMutex // protects field below
+	hashGlobs  map[string]globs
+	globStatus map[string]util.Set // glob -> hashes where this glob hasn't changed
+
+	closed bool
+}
+
+// New returns a new GlobWatcher instance
+func New(logger hclog.Logger, repoRoot turbopath.AbsoluteSystemPath, cookieWaiter filewatcher.CookieWaiter) *GlobWatcher {
+	return &GlobWatcher{
+		logger:       logger,
+		repoRoot:     repoRoot,
+		cookieWaiter: cookieWaiter,
+		hashGlobs:    make(map[string]globs),
+		globStatus:   make(map[string]util.Set),
+	}
+}
+
+func (g *GlobWatcher) setClosed() {
+	g.mu.Lock()
+	g.closed = true
+	g.mu.Unlock()
+}
+
+func (g *GlobWatcher) isClosed() bool {
+	g.mu.RLock()
+	defer g.mu.RUnlock()
+	return g.closed
+}
+
+// WatchGlobs registers the given set of globs to be watched for changes and grouped
+// under the given hash. This method pairs with GetChangedGlobs to determine which globs
+// out of a set of candidates have changed since WatchGlobs was called for the same hash.
+func (g *GlobWatcher) WatchGlobs(hash string, globsToWatch fs.TaskOutputs) error {
+	if g.isClosed() {
+		return ErrClosed
+	}
+	// Wait for a cookie here
+	// that will ensure that we have seen all filesystem writes
+	// *by the calling client*. Other tasks _could_ write to the
+	// same output directories, however we are relying on task
+	// execution dependencies to prevent that.
+	if err := g.cookieWaiter.WaitForCookie(); err != nil {
+		return err
+	}
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	g.hashGlobs[hash] = globs{
+		Inclusions: util.SetFromStrings(globsToWatch.Inclusions),
+		Exclusions: util.SetFromStrings(globsToWatch.Exclusions),
+	}
+
+	for _, glob := range globsToWatch.Inclusions {
+		existing, ok := g.globStatus[glob]
+		if !ok {
+			existing = make(util.Set)
+		}
+		existing.Add(hash)
+		g.globStatus[glob] = existing
+	}
+	return nil
+}
+
+// GetChangedGlobs returns the subset of the given candidates that we are not currently
+// tracking as "unchanged".
+func (g *GlobWatcher) GetChangedGlobs(hash string, candidates []string) ([]string, error) {
+	if g.isClosed() {
+		// If filewatching has crashed, return all candidates as changed.
+		return candidates, nil
+	}
+	// Wait for a cookie here
+	// that will ensure that we have seen all filesystem writes
+	// *by the calling client*. Other tasks _could_ write to the
+	// same output directories, however we are relying on task
+	// execution dependencies to prevent that.
+	if err := g.cookieWaiter.WaitForCookie(); err != nil {
+		return nil, err
+	}
+	// hashGlobs tracks all of the unchanged globs for a given hash
+	// If hashGlobs doesn't have our hash, either everything has changed,
+	// or we were never tracking it. Either way, consider all the candidates
+	// to be changed globs.
+	g.mu.RLock()
+	defer g.mu.RUnlock()
+	globsToCheck, ok := g.hashGlobs[hash]
+	if !ok {
+		return candidates, nil
+	}
+	allGlobs := util.SetFromStrings(candidates)
+	diff := allGlobs.Difference(globsToCheck.Inclusions)
+
+	return diff.UnsafeListOfStrings(), nil
+}
+
+// OnFileWatchEvent implements FileWatchClient.OnFileWatchEvent
+// On a file change, check if we have a glob that matches this file. Invalidate
+// any matching globs, and remove them from the set of unchanged globs for the corresponding
+// hashes. If this is the last glob for a hash, remove the hash from being tracked.
+func (g *GlobWatcher) OnFileWatchEvent(ev filewatcher.Event) {
+	// At this point, we don't care what the Op is, any Op represents a change
+	// that should invalidate matching globs
+	g.logger.Trace(fmt.Sprintf("Got fsnotify event %v", ev))
+	absolutePath := ev.Path
+	repoRelativePath, err := g.repoRoot.RelativePathString(absolutePath.ToStringDuringMigration())
+	if err != nil {
+		g.logger.Debug(fmt.Sprintf("could not get relative path from %v to %v: %v", g.repoRoot, absolutePath, err))
+		return
+	}
+	g.mu.Lock()
+	defer g.mu.Unlock()
+	for glob, hashStatus := range g.globStatus {
+		matches, err := doublestar.Match(glob, filepath.ToSlash(repoRelativePath))
+		if err != nil {
+			g.logger.Error(fmt.Sprintf("failed to check path %v against glob %v: %v", repoRelativePath, glob, err))
+			continue
+		}
+		// If this glob matches, we know that it has changed for every hash that included this glob
+		// and is not excluded by a hash's exclusion globs.
+		// So, we can delete this glob from every hash tracking it as well as stop watching this glob.
+		// To stop watching, we unref each of the directories corresponding to this glob.
+		if matches {
+			for hashUntyped := range hashStatus {
+				hash := hashUntyped.(string)
+				hashGlobs, ok := g.hashGlobs[hash]
+
+				if !ok {
+					g.logger.Warn(fmt.Sprintf("failed to find hash %v referenced from glob %v", hash, glob))
+					continue
+				}
+
+				isExcluded := false
+				// Check if we've excluded this path by going through exclusion globs
+				for exclusionGlob := range hashGlobs.Exclusions {
+					matches, err := doublestar.Match(exclusionGlob.(string), filepath.ToSlash(repoRelativePath))
+					if err != nil {
+						g.logger.Error(fmt.Sprintf("failed to check path %v against glob %v: %v", repoRelativePath, glob, err))
+						continue
+					}
+
+					if matches {
+						isExcluded = true
+						break
+					}
+				}
+
+				// If we have excluded this path, then we skip it
+				if isExcluded {
+					continue
+				}
+
+				// We delete hash from the globStatus entry
+				g.globStatus[glob].Delete(hash)
+
+				// If we've deleted the last hash for a glob in globStatus, delete the whole glob entry
+				if len(g.globStatus[glob]) == 0 {
+					delete(g.globStatus, glob)
+				}
+
+				hashGlobs.Inclusions.Delete(glob)
+				// If we've deleted the last glob for a hash, delete the whole hash entry
+				if hashGlobs.Inclusions.Len() == 0 {
+					delete(g.hashGlobs, hash)
+				}
+			}
+		}
+	}
+}
+
+// OnFileWatchError implements FileWatchClient.OnFileWatchError
+func (g *GlobWatcher) OnFileWatchError(err error) {
+	g.logger.Error(fmt.Sprintf("file watching received an error: %v", err))
+}
+
+// OnFileWatchClosed implements FileWatchClient.OnFileWatchClosed
+func (g *GlobWatcher) OnFileWatchClosed() {
+	g.setClosed()
+	g.logger.Warn("GlobWatching is closing due to file watching closing")
+}
diff --git a/cli/internal/globwatcher/globwatcher_test.go b/cli/internal/globwatcher/globwatcher_test.go
new file mode 100644
index 0000000..6fb89a7
--- /dev/null
+++ b/cli/internal/globwatcher/globwatcher_test.go
@@ -0,0 +1,232 @@
+package globwatcher
+
+import (
+	"testing"
+
+	"github.com/hashicorp/go-hclog"
+	"github.com/vercel/turbo/cli/internal/filewatcher"
+	"github.com/vercel/turbo/cli/internal/fs"
+	"github.com/vercel/turbo/cli/internal/turbopath"
+	"gotest.tools/v3/assert"
+)
+
+func setup(t *testing.T, repoRoot turbopath.AbsoluteSystemPath) {
+	// Directory layout:
+	// <repoRoot>/
+	//   my-pkg/
+	//     irrelevant
+	//     dist/
+	//       dist-file
+	//       distChild/
+	//         child-file
+	//     .next/
+	//       next-file
+	distPath := repoRoot.UntypedJoin("my-pkg", "dist")
+	childFilePath := distPath.UntypedJoin("distChild", "child-file")
+	err := childFilePath.EnsureDir()
+	assert.NilError(t, err, "EnsureDir")
+	f, err := childFilePath.Create()
+	assert.NilError(t, err, "Create")
+	err = f.Close()
+	assert.NilError(t, err, "Close")
+	distFilePath := repoRoot.UntypedJoin("my-pkg", "dist", "dist-file")
+	f, err = distFilePath.Create()
+	assert.NilError(t, err, "Create")
+	err = f.Close()
+	assert.NilError(t, err, "Close")
+	nextFilePath := repoRoot.UntypedJoin("my-pkg", ".next", "next-file")
+	err = nextFilePath.EnsureDir()
+	assert.NilError(t, err, "EnsureDir")
+	f, err = nextFilePath.Create()
+	assert.NilError(t, err, "Create")
+	err = f.Close()
+	assert.NilError(t, err, "Close")
+	irrelevantPath := repoRoot.UntypedJoin("my-pkg", "irrelevant")
+	f, err = irrelevantPath.Create()
+	assert.NilError(t, err, "Create")
+	err = f.Close()
+	assert.NilError(t, err, "Close")
+}
+
+type noopCookieWaiter struct{}
+
+func (*noopCookieWaiter) WaitForCookie() error {
+	return nil
+}
+
+var _noopCookieWaiter = &noopCookieWaiter{}
+
+func TestTrackOutputs(t *testing.T) {
+	logger := hclog.Default()
+
+	repoRootRaw := t.TempDir()
+	repoRoot := fs.AbsoluteSystemPathFromUpstream(repoRootRaw)
+
+	setup(t, repoRoot)
+
+	globWatcher := New(logger, repoRoot, _noopCookieWaiter)
+
+	globs := fs.TaskOutputs{
+		Inclusions: []string{
+			"my-pkg/dist/**",
+			"my-pkg/.next/**",
+		},
+		Exclusions: []string{"my-pkg/.next/cache/**"},
+	}
+
+	hash := "the-hash"
+	err := globWatcher.WatchGlobs(hash, globs)
+	assert.NilError(t, err, "WatchGlobs")
+
+	changed, err := globWatcher.GetChangedGlobs(hash, globs.Inclusions)
+	assert.NilError(t, err, "GetChangedGlobs")
+	assert.Equal(t, 0, len(changed), "Expected no changed paths")
+
+	// Make an irrelevant change
+	globWatcher.OnFileWatchEvent(filewatcher.Event{
+		EventType: filewatcher.FileAdded,
+		Path:      repoRoot.UntypedJoin("my-pkg", "irrelevant"),
+	})
+
+	changed, err = globWatcher.GetChangedGlobs(hash, globs.Inclusions)
+	assert.NilError(t, err, "GetChangedGlobs")
+	assert.Equal(t, 0, len(changed), "Expected no changed paths")
+
+	// Make an excluded change
+	globWatcher.OnFileWatchEvent(filewatcher.Event{
+		EventType: filewatcher.FileAdded,
+		Path:      repoRoot.Join("my-pkg", ".next", "cache", "foo"),
+	})
+
+	changed, err = globWatcher.GetChangedGlobs(hash, globs.Inclusions)
+	assert.NilError(t, err, "GetChangedGlobs")
+	assert.Equal(t, 0, len(changed), "Expected no changed paths")
+
+	// Make a relevant change
+	globWatcher.OnFileWatchEvent(filewatcher.Event{
+		EventType: filewatcher.FileAdded,
+		Path:      repoRoot.UntypedJoin("my-pkg", "dist", "foo"),
+	})
+
+	changed, err = globWatcher.GetChangedGlobs(hash, globs.Inclusions)
+	assert.NilError(t, err, "GetChangedGlobs")
+	assert.Equal(t, 1, len(changed), "Expected one changed path remaining")
+	expected := "my-pkg/dist/**"
+	assert.Equal(t, expected, changed[0], "Expected dist glob to have changed")
+
+	// Change a file matching the other glob
+	globWatcher.OnFileWatchEvent(filewatcher.Event{
+		EventType: filewatcher.FileAdded,
+		Path:      repoRoot.UntypedJoin("my-pkg", ".next", "foo"),
+	})
+	// We should no longer be watching anything, since both globs have
+	// registered changes
+	if len(globWatcher.hashGlobs) != 0 {
+		t.Errorf("expected to not track any hashes, found %v", globWatcher.hashGlobs)
+	}
+
+	// Both globs have changed, we should have stopped tracking
+	// this hash
+	changed, err = globWatcher.GetChangedGlobs(hash, globs.Inclusions)
+	assert.NilError(t, err, "GetChangedGlobs")
+	assert.DeepEqual(t, globs.Inclusions, changed)
+}
+
+func TestTrackMultipleHashes(t *testing.T) {
+	logger := hclog.Default()
+
+	repoRootRaw := t.TempDir()
+	repoRoot := fs.AbsoluteSystemPathFromUpstream(repoRootRaw)
+
+	setup(t, repoRoot)
+
+	globWatcher := New(logger, repoRoot, _noopCookieWaiter)
+
+	globs := fs.TaskOutputs{
+		Inclusions: []string{
+			"my-pkg/dist/**",
+			"my-pkg/.next/**",
+		},
+	}
+
+	hash := "the-hash"
+	err := globWatcher.WatchGlobs(hash, globs)
+	assert.NilError(t, err, "WatchGlobs")
+
+	secondGlobs := fs.TaskOutputs{
+		Inclusions: []string{
+			"my-pkg/.next/**",
+		},
+		Exclusions: []string{"my-pkg/.next/cache/**"},
+	}
+
+	secondHash := "the-second-hash"
+	err = globWatcher.WatchGlobs(secondHash, secondGlobs)
+	assert.NilError(t, err, "WatchGlobs")
+
+	changed, err := globWatcher.GetChangedGlobs(hash, globs.Inclusions)
+	assert.NilError(t, err, "GetChangedGlobs")
+	assert.Equal(t, 0, len(changed), "Expected no changed paths")
+
+	changed, err = globWatcher.GetChangedGlobs(secondHash, secondGlobs.Inclusions)
+	assert.NilError(t, err, "GetChangedGlobs")
+	assert.Equal(t, 0, len(changed), "Expected no changed paths")
+
+	// Make a change that is excluded in one of the hashes but not in the other
+	globWatcher.OnFileWatchEvent(filewatcher.Event{
+		EventType: filewatcher.FileAdded,
+		Path:      repoRoot.UntypedJoin("my-pkg", ".next", "cache", "foo"),
+	})
+
+	changed, err = globWatcher.GetChangedGlobs(hash, globs.Inclusions)
+	assert.NilError(t, err, "GetChangedGlobs")
+	assert.Equal(t, 1, len(changed), "Expected one changed path remaining")
+
+	changed, err = globWatcher.GetChangedGlobs(secondHash, secondGlobs.Inclusions)
+	assert.NilError(t, err, "GetChangedGlobs")
+	assert.Equal(t, 0, len(changed), "Expected no changed paths")
+
+	assert.Equal(t, 1, len(globWatcher.globStatus["my-pkg/.next/**"]), "Expected to be still watching `my-pkg/.next/**`")
+
+	// Make a change for secondHash
+	globWatcher.OnFileWatchEvent(filewatcher.Event{
+		EventType: filewatcher.FileAdded,
+		Path:      repoRoot.UntypedJoin("my-pkg", ".next", "bar"),
+	})
+
+	assert.Equal(t, 0, len(globWatcher.globStatus["my-pkg/.next/**"]), "Expected to be no longer watching `my-pkg/.next/**`")
+}
+
+func TestWatchSingleFile(t *testing.T) {
+	logger := hclog.Default()
+
+	repoRoot := fs.AbsoluteSystemPathFromUpstream(t.TempDir())
+
+	setup(t, repoRoot)
+
+	//watcher := newTestWatcher()
+	globWatcher := New(logger, repoRoot, _noopCookieWaiter)
+	globs := fs.TaskOutputs{
+		Inclusions: []string{"my-pkg/.next/next-file"},
+		Exclusions: []string{},
+	}
+	hash := "the-hash"
+	err := globWatcher.WatchGlobs(hash, globs)
+	assert.NilError(t, err, "WatchGlobs")
+
+	assert.Equal(t, 1, len(globWatcher.hashGlobs))
+
+	// A change to an irrelevant file
+	globWatcher.OnFileWatchEvent(filewatcher.Event{
+		EventType: filewatcher.FileAdded,
+		Path:      repoRoot.UntypedJoin("my-pkg", ".next", "foo"),
+	})
+	assert.Equal(t, 1, len(globWatcher.hashGlobs))
+
+	// Change the watched file
+	globWatcher.OnFileWatchEvent(filewatcher.Event{
+		EventType: filewatcher.FileAdded,
+		Path:      repoRoot.UntypedJoin("my-pkg", ".next", "next-file"),
+	})
+	assert.Equal(t, 0, len(globWatcher.hashGlobs))
+}