update jam summarize to omit stacks information if none are present i…

…n buildpack toml

- Lets us use this command to get a summary of metabuildpack .tgz files.

Signed-off-by: Ryan Moran <[email protected]>

cargo/jam/internal/formatter.go

@@ -86,8 +86,10 @@ func (f Formatter) Markdown(dependencies []cargo.ConfigMetadataDependency, defau
 
 	sort.Strings(stacks)
 
-	fmt.Fprintf(f.writer, "Supported stacks:\n| name |\n|-|\n")
-	for _, s := range stacks {
-		fmt.Fprintf(f.writer, "| %s |\n", s)
+	if len(stacks) > 0 {
+		fmt.Fprintf(f.writer, "Supported stacks:\n| name |\n|-|\n")
+		for _, s := range stacks {
+			fmt.Fprintf(f.writer, "| %s |\n", s)
+		}
 	}
 }

cargo/jam/internal/formatter_test.go

@@ -92,6 +92,53 @@ Supported stacks:
 |-|
 | other-stack |
 | some-stack |
+`))
+			})
+		})
+
+		context("when stacks are empty", func() {
+			it("returns a list of dependencies", func() {
+				dependencies := []cargo.ConfigMetadataDependency{
+					{
+						ID:      "some-dependency",
+						Stacks:  []string{"some-stack"},
+						Version: "1.2.3",
+					},
+					{
+						ID:      "some-dependency",
+						Stacks:  []string{"other-stack"},
+						Version: "1.2.3",
+					},
+					{
+						ID:      "other-dependency",
+						Stacks:  []string{"some-stack", "other-stack"},
+						Version: "2.3.4",
+					},
+					{
+						ID:      "other-dependency",
+						Stacks:  []string{"other-stack"},
+						Version: "2.3.5",
+					},
+				}
+				defaults := map[string]string{
+					"some-dependency":  "1.2.x",
+					"other-dependency": "2.3.x",
+				}
+
+				formatter.Markdown(dependencies, defaults, nil)
+				Expect(buffer.String()).To(Equal(`Dependencies:
+| name | version | stacks |
+|-|-|-|
+| other-dependency | 2.3.5 | other-stack |
+| other-dependency | 2.3.4 | other-stack, some-stack |
+| some-dependency | 1.2.3 | other-stack, some-stack |
+
+Default dependencies:
+| name | version |
+|-|-|
+| other-dependency | 2.3.x |
+| some-dependency | 1.2.x |
+
 `))
 			})
 		})