dockerfile: rework oci context tests to include workdir

To test the behavior in the previous commit, we check that workdir
inheritance works by setting it in the base image. Additionally, we add
a new test to check the exported results of images that use these oci
contexts.

Signed-off-by: Justin Chadwell <me@jedevc.com>

frontend/dockerfile/dockerfile_test.go

@@ -119,6 +119,7 @@ var allTests = integration.TestFuncs(
 	testNamedImageContextTimestamps,
 	testNamedLocalContext,
 	testNamedOCILayoutContext,
+	testNamedOCILayoutContextExport,
 	testNamedInputContext,
 	testNamedMultiplatformInputContext,
 	testEmptyDestDir,
@@ -5426,6 +5427,7 @@ func testNamedOCILayoutContext(t *testing.T, sb integration.Sandbox) {
 
 	ociDockerfile := []byte(`
 	FROM busybox:latest
+	WORKDIR /test
 	RUN sh -c "echo -n first > out"
 	RUN sh -c "echo -n second > out2"
 	ENV foo=bar
@@ -5490,12 +5492,14 @@ func testNamedOCILayoutContext(t *testing.T, sb integration.Sandbox) {
 	//    when we `COPY --from=imported`, it should have the content of `/outfoo` as `"bar"`
 	dockerfile := []byte(`
 FROM busybox AS base
-RUN cat /etc/alpine-release > /out
+RUN cat /etc/alpine-release > out
+
 FROM foo AS imported
-RUN echo -n $foo > /outfoo
+RUN echo -n $foo > outfoo
+
 FROM scratch
-COPY --from=base /o* /
-COPY --from=imported /outfoo /
+COPY --from=base /test/o* /
+COPY --from=imported /test/outfoo /
 `)
 
 	dir, err := integration.Tmpdir(
@@ -5543,6 +5547,117 @@ COPY --from=imported /outfoo /
 	require.Equal(t, []byte("bar"), dt)
 }
 
+func testNamedOCILayoutContextExport(t *testing.T, sb integration.Sandbox) {
+	ctx := sb.Context()
+
+	c, err := client.New(ctx, sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	ocidir := t.TempDir()
+
+	dockerfile := []byte(`
+FROM scratch
+WORKDIR /test
+ENV foo=bar
+	`)
+	dir, err := integration.Tmpdir(
+		t,
+		fstest.CreateFile("Dockerfile", dockerfile, 0600),
+	)
+	require.NoError(t, err)
+
+	f := getFrontend(t, sb)
+
+	outW := bytes.NewBuffer(nil)
+	_, err = f.Solve(sb.Context(), c, client.SolveOpt{
+		LocalDirs: map[string]string{
+			builder.DefaultLocalNameDockerfile: dir,
+			builder.DefaultLocalNameContext:    dir,
+		},
+		Exports: []client.ExportEntry{{
+			Type:   client.ExporterOCI,
+			Output: fixedWriteCloser(nopWriteCloser{outW}),
+		}},
+	}, nil)
+	require.NoError(t, err)
+
+	m, err := testutil.ReadTarToMap(outW.Bytes(), false)
+	require.NoError(t, err)
+
+	for filename, content := range m {
+		fullFilename := path.Join(ocidir, filename)
+		err = os.MkdirAll(path.Dir(fullFilename), 0755)
+		require.NoError(t, err)
+		if content.Header.FileInfo().IsDir() {
+			err = os.MkdirAll(fullFilename, 0755)
+			require.NoError(t, err)
+		} else {
+			err = os.WriteFile(fullFilename, content.Data, 0644)
+			require.NoError(t, err)
+		}
+	}
+
+	var index ocispecs.Index
+	err = json.Unmarshal(m["index.json"].Data, &index)
+	require.NoError(t, err)
+	require.Equal(t, 1, len(index.Manifests))
+	digest := index.Manifests[0].Digest.Hex()
+
+	store, err := local.NewStore(ocidir)
+	ociID := "ocione"
+	require.NoError(t, err)
+
+	dockerfile = []byte(`
+FROM nonexistent AS base
+`)
+
+	dir, err = integration.Tmpdir(
+		t,
+		fstest.CreateFile("Dockerfile", dockerfile, 0600),
+	)
+	require.NoError(t, err)
+
+	outW = bytes.NewBuffer(nil)
+	_, err = f.Solve(sb.Context(), c, client.SolveOpt{
+		FrontendAttrs: map[string]string{
+			"context:nonexistent": fmt.Sprintf("oci-layout:%s@sha256:%s", ociID, digest),
+		},
+		LocalDirs: map[string]string{
+			builder.DefaultLocalNameDockerfile: dir,
+			builder.DefaultLocalNameContext:    dir,
+		},
+		OCIStores: map[string]content.Store{
+			ociID: store,
+		},
+		Exports: []client.ExportEntry{
+			{
+				Type:   client.ExporterOCI,
+				Output: fixedWriteCloser(nopWriteCloser{outW}),
+			},
+		},
+	}, nil)
+	require.NoError(t, err)
+
+	m, err = testutil.ReadTarToMap(outW.Bytes(), false)
+	require.NoError(t, err)
+
+	err = json.Unmarshal(m["index.json"].Data, &index)
+	require.NoError(t, err)
+	require.Equal(t, 1, len(index.Manifests))
+	digest = index.Manifests[0].Digest.Hex()
+
+	var mfst ocispecs.Manifest
+	require.NoError(t, json.Unmarshal(m["blobs/sha256/"+digest].Data, &mfst))
+	digest = mfst.Config.Digest.Hex()
+
+	var cfg ocispecs.Image
+	require.NoError(t, json.Unmarshal(m["blobs/sha256/"+digest].Data, &cfg))
+
+	require.Equal(t, "/test", cfg.Config.WorkingDir)
+	require.Contains(t, cfg.Config.Env, "foo=bar")
+}
+
 func testNamedInputContext(t *testing.T, sb integration.Sandbox) {
 	ctx := sb.Context()