Check if local exports exist (#197)

Check if local exports exist during diffing. For tar, the file must
exist. For local, the directory must exist and be populated.

Fixes https://github.com/pulumi/pulumi-docker-build/issues/177.

CHANGELOG.md

@@ -5,6 +5,11 @@
 - Refreshing an `Index` resource will no longer fail if its stored credentials
   have expired. (https://github.com/pulumi/pulumi-docker-build/pull/194)
 
+### Changed
+
+- Local and tar exporters will now trigger an update if an export doesn't exist
+  at the expected path. (https://github.com/pulumi/pulumi-docker-build/pull/195)
+
 ## 0.0.5 (2024-08-08)
 
 ### Fixed

provider/internal/export.go

@@ -17,6 +17,7 @@ package internal
 import (
 	"errors"
 	"fmt"
+	"os"
 	"slices"
 	"strings"
 
@@ -353,6 +354,19 @@ func (e *ExportLocal) Annotate(a infer.Annotator) {
 	a.Describe(&e.Dest, "Output path.")
 }
 
+// Exists returns true if the exported directory exists and is populated with
+// some files.
+func (e *ExportLocal) Exists() bool {
+	if e == nil {
+		return true // Degenerate case.
+	}
+	files, err := os.ReadDir(e.Dest)
+	if err != nil {
+		return false
+	}
+	return len(files) > 0
+}
+
 // ExportTar is an export that uses the tar format for exporting.
 type ExportTar struct {
 	ExportLocal
@@ -365,6 +379,15 @@ func (e *ExportTar) String() string {
 	return "type=tar,dest=" + e.Dest
 }
 
+// Exists returns true if a file exists at the expected path.
+func (e *ExportTar) Exists() bool {
+	if e == nil {
+		return true // Degenerate case.
+	}
+	_, err := os.Stat(e.Dest)
+	return err == nil
+}
+
 // ExportWithOCI is an export that support OCI media types.
 type ExportWithOCI struct {
 	OCI *bool `pulumi:"ociMediaTypes,optional"`

provider/internal/image.go

@@ -913,6 +913,12 @@ func (*Image) Diff(
 	if fmt.Sprint(olds.Exports) != fmt.Sprint(news.Exports) {
 		diff["exports"] = update
 	}
+	// Confirm local exports exist.
+	for idx, e := range news.Exports {
+		if !e.Local.Exists() || !e.Tar.Exists() {
+			diff[fmt.Sprintf("exports[%d]", idx)] = update
+		}
+	}
 	if !reflect.DeepEqual(olds.Labels, news.Labels) {
 		diff["labels"] = update
 	}

provider/internal/image_test.go

@@ -757,6 +757,38 @@ func TestImageDiff(t *testing.T) {
 			},
 			wantChanges: true,
 		},
+		{
+			name: "diff if local export doesn't exist",
+			olds: func(t *testing.T, state ImageState) ImageState {
+				state.Exports = []Export{
+					{Local: &ExportLocal{Dest: "not-real"}},
+				}
+				return state
+			},
+			news: func(_ *testing.T, args ImageArgs) ImageArgs {
+				args.Exports = []Export{
+					{Local: &ExportLocal{Dest: "not-real"}},
+				}
+				return args
+			},
+			wantChanges: true,
+		},
+		{
+			name: "diff if tar export doesn't exist",
+			olds: func(t *testing.T, state ImageState) ImageState {
+				state.Exports = []Export{
+					{Tar: &ExportTar{ExportLocal: ExportLocal{Dest: "not-real"}}},
+				}
+				return state
+			},
+			news: func(_ *testing.T, args ImageArgs) ImageArgs {
+				args.Exports = []Export{
+					{Tar: &ExportTar{ExportLocal: ExportLocal{Dest: "not-real"}}},
+				}
+				return args
+			},
+			wantChanges: true,
+		},
 	}
 
 	s := newServer(nil)