feat: add --separate flag for split representation of external images

README.md

@@ -107,6 +107,7 @@ dockerfilegraph
 - `--output svg|png|pdf` - Choose your output format
 - `--legend` - Add a legend explaining the notation
 - `--layers` - Show all Docker layers
+- `--separate ubuntu,alpine` - Display selected external images as separate nodes per usage, reducing edge clutter
 
 **All Available Options:**
 
@@ -131,6 +132,7 @@ Flags:
   -o, --output                  output file format, one of: canon, dot, pdf, png, raw, svg (default pdf)
   -r, --ranksep float           minimum separation between ranks (default 0.5)
       --scratch                 how to handle scratch images, one of: collapsed, hidden, separated (default collapsed)
+      --separate strings        external images to display as separate nodes per usage (e.g. --separate ubuntu,alpine)
   -u, --unflatten uint          stagger length of leaf edges between [1,u] (default 0)
       --version                 display the version of dockerfilegraph
 ```

internal/cmd/root.go

@@ -27,6 +27,7 @@ type cliFlags struct {
 	output         enum
 	ranksep        float64
 	scratch        enum
+	separate       []string
 	unflatten      uint
 	version        bool
 }
@@ -67,14 +68,15 @@ It creates a visual graph representation of the build process.`,
 			}
 
 			// Determine scratch mode from flag
-			scratchMode := f.scratch.String()
+			scratchMode := scratchModeFromString(f.scratch.String())
 
 			// Load and parse the Dockerfile.
 			dockerfile, err := dockerfile2dot.LoadAndParseDockerfile(
 				inputFS,
 				f.filename,
 				int(f.maxLabelLength),
 				scratchMode,
+				f.separate,
 			)
 			if err != nil {
 				return
@@ -93,8 +95,8 @@ It creates a visual graph representation of the build process.`,
 				f.layers,
 				f.legend,
 				int(f.maxLabelLength),
-				fmt.Sprintf("%.2f", f.nodesep),
-				fmt.Sprintf("%.2f", f.ranksep),
+				f.nodesep,
+				f.ranksep,
 			)
 			if err != nil {
 				return
@@ -248,6 +250,13 @@ It creates a visual graph representation of the build process.`,
 		"how to handle scratch images, one of: "+strings.Join(f.scratch.AllowedValues(), ", "),
 	)
 
+	rootCmd.Flags().StringSliceVar(
+		&f.separate,
+		"separate",
+		nil,
+		"external images to display as separate nodes per usage (e.g. --separate ubuntu,alpine)",
+	)
+
 	rootCmd.Flags().UintVarP(
 		&f.unflatten,
 		"unflatten",
@@ -329,3 +338,15 @@ func checkFlags(maxLabelLength uint) error {
 	}
 	return nil
 }
+
+// scratchModeFromString converts a validated enum string to a ScratchMode constant.
+func scratchModeFromString(s string) dockerfile2dot.ScratchMode {
+	switch s {
+	case "separated":
+		return dockerfile2dot.ScratchSeparated
+	case "hidden":
+		return dockerfile2dot.ScratchHidden
+	default:
+		return dockerfile2dot.ScratchCollapsed
+	}
+}

internal/cmd/root_test.go

@@ -39,6 +39,7 @@ Flags:
   -o, --output                  output file format, one of: canon, dot, pdf, png, raw, svg (default pdf)
   -r, --ranksep float           minimum separation between ranks (default 0.5)
       --scratch                 how to handle scratch images, one of: collapsed, hidden, separated (default collapsed)
+      --separate strings        external images to display as separate nodes per usage (e.g. --separate ubuntu,alpine)
   -u, --unflatten uint          stagger length of leaf edges between [1,u] (default 0)
       --version                 display the version of dockerfilegraph
 `
@@ -558,6 +559,65 @@ It creates a visual graph representation of the build process.
 			wantErr:      true,
 			wantOutRegex: `invalid argument "invalid" for "--scratch" flag: invalid value: invalid`,
 		},
+		{
+			name:    "separate flag single image",
+			cliArgs: []string{"--separate", "ubuntu:latest", "-o", "raw"},
+			dockerfileContent: "FROM ubuntu:latest AS base\nRUN echo base\n\n" +
+				"FROM ubuntu:latest AS other\nRUN echo other\n\n" +
+				"FROM alpine AS final\nCOPY --from=base . .\nCOPY --from=other . .\n",
+			wantOut:     "Successfully created Dockerfile.raw\n",
+			wantOutFile: "Dockerfile.raw",
+			wantOutFileContent: `digraph G {
+	compound=true;
+	nodesep=1.00;
+	rankdir=LR;
+	ranksep=0.50;
+	external_image_0->stage_0;
+	external_image_1->stage_1;
+	external_image_2->stage_2;
+	stage_0->stage_2[ arrowhead=empty, style=dashed ];
+	stage_1->stage_2[ arrowhead=empty, style=dashed ];
+	external_image_0 [ color=grey20, fontcolor=grey20, label="ubuntu:latest", shape=box, style="dashed,rounded", width=2 ];
+	external_image_1 [ color=grey20, fontcolor=grey20, label="ubuntu:latest", shape=box, style="dashed,rounded", width=2 ];
+	external_image_2 [ color=grey20, fontcolor=grey20, label="alpine", shape=box, style="dashed,rounded", width=2 ];
+	stage_0 [ label="base", shape=box, style=rounded, width=2 ];
+	stage_1 [ label="other", shape=box, style=rounded, width=2 ];
+	stage_2 [ fillcolor=grey90, label="final", shape=box, style="filled,rounded", width=2 ];
+
+}
+`,
+		},
+		{
+			name:    "separate flag multiple images",
+			cliArgs: []string{"--separate", "ubuntu:latest,alpine", "-o", "raw"},
+			dockerfileContent: "FROM ubuntu:latest AS base\nRUN echo base\n\n" +
+				"FROM alpine AS mid\nRUN echo mid\n\n" +
+				"FROM ubuntu:latest AS other\nRUN echo other\n\n" +
+				"FROM alpine AS final\nCOPY --from=base . .\n",
+			wantOut:     "Successfully created Dockerfile.raw\n",
+			wantOutFile: "Dockerfile.raw",
+			wantOutFileContent: `digraph G {
+	compound=true;
+	nodesep=1.00;
+	rankdir=LR;
+	ranksep=0.50;
+	external_image_0->stage_0;
+	external_image_1->stage_1;
+	external_image_2->stage_2;
+	external_image_3->stage_3;
+	stage_0->stage_3[ arrowhead=empty, style=dashed ];
+	external_image_0 [ color=grey20, fontcolor=grey20, label="ubuntu:latest", shape=box, style="dashed,rounded", width=2 ];
+	external_image_1 [ color=grey20, fontcolor=grey20, label="alpine", shape=box, style="dashed,rounded", width=2 ];
+	external_image_2 [ color=grey20, fontcolor=grey20, label="ubuntu:latest", shape=box, style="dashed,rounded", width=2 ];
+	external_image_3 [ color=grey20, fontcolor=grey20, label="alpine", shape=box, style="dashed,rounded", width=2 ];
+	stage_0 [ label="base", shape=box, style=rounded, width=2 ];
+	stage_1 [ label="mid", shape=box, style=rounded, width=2 ];
+	stage_2 [ label="other", shape=box, style=rounded, width=2 ];
+	stage_3 [ fillcolor=grey90, label="final", shape=box, style="filled,rounded", width=2 ];
+
+}
+`,
+		},
 	}
 
 	for _, tt := range tests {

internal/dockerfile2dot/build.go

@@ -17,8 +17,8 @@ func BuildDotFile(
 	layers bool,
 	legend bool,
 	maxLabelLength int,
-	nodesep string,
-	ranksep string,
+	nodesep float64,
+	ranksep float64,
 ) (string, error) {
 	// Create a new graph
 	graph := gographviz.NewEscape()
@@ -33,9 +33,9 @@ func BuildDotFile(
 	set(graph.SetName("G"))
 	set(graph.SetDir(true))
 	set(graph.AddAttr("G", "compound", "true")) // allow edges between clusters
-	set(graph.AddAttr("G", "nodesep", nodesep))
+	set(graph.AddAttr("G", "nodesep", fmt.Sprintf("%.2f", nodesep)))
 	set(graph.AddAttr("G", "rankdir", "LR"))
-	set(graph.AddAttr("G", "ranksep", ranksep))
+	set(graph.AddAttr("G", "ranksep", fmt.Sprintf("%.2f", ranksep)))
 	if concentrate {
 		set(graph.AddAttr("G", "concentrate", "true"))
 	}

internal/dockerfile2dot/build_test.go

@@ -58,7 +58,7 @@ func TestBuildDotFileErrors(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			_, err := BuildDotFile(
-				tt.simplifiedDockerfile, false, "default", tt.layers, false, 20, "0.5", "0.5",
+				tt.simplifiedDockerfile, false, "default", tt.layers, false, 20, 0.5, 0.5,
 			)
 			if err == nil {
 				t.Error("BuildDotFile() expected an error, got nil")
@@ -75,8 +75,8 @@ func TestBuildDotFile(t *testing.T) {
 		layers               bool
 		legend               bool
 		maxLabelLength       int
-		nodesep              string
-		ranksep              string
+		nodesep              float64
+		ranksep              float64
 	}
 	tests := []struct {
 		name         string
@@ -113,8 +113,8 @@ func TestBuildDotFile(t *testing.T) {
 				edgestyle:      "default",
 				legend:         true,
 				maxLabelLength: 20,
-				nodesep:        "0.5",
-				ranksep:        "0.5",
+				nodesep:        0.5,
+				ranksep:        0.5,
 			},
 			wantContains: "release",
 		},
@@ -148,8 +148,8 @@ func TestBuildDotFile(t *testing.T) {
 				edgestyle:      "default",
 				layers:         true,
 				maxLabelLength: 20,
-				nodesep:        "0.5",
-				ranksep:        "0.5",
+				nodesep:        0.5,
+				ranksep:        0.5,
 			},
 			wantContains: "release",
 		},
@@ -193,8 +193,8 @@ func TestBuildDotFile(t *testing.T) {
 				layers:         false,
 				legend:         false,
 				maxLabelLength: 20,
-				nodesep:        "0.5",
-				ranksep:        "0.5",
+				nodesep:        0.5,
+				ranksep:        0.5,
 			},
 			wantContains: `external_image_0 [ color=grey20, fontcolor=grey20, label="scratch", shape=box, ` +
 				`style="dashed,rounded", width=2 ];