Handle custom invocation images without #PORTER_INIT (#2998)

* Handle custom Dockerfile without PORTER_INIT

The documentation says that if the PORTER_INIT section is missing on the
custom dockerfile, it will be placed right after the FROM section. This
was not the case, instead it was place at the end of the file, resulting
in a dockerfile not working with Porter

Signed-off-by: Kim Christensen <kimworking@gmail.com>

---------

Signed-off-by: Kim Christensen <kimworking@gmail.com>

pkg/build/dockerfile-generator.go

@@ -254,7 +254,7 @@ func (g *DockerfileGenerator) copyMixin(mixin string) error {
 
 func (g *DockerfileGenerator) getIndexOfToken(lines []string, token string) int {
 	for lineNumber, lineContent := range lines {
-		if token == strings.TrimSpace(lineContent) {
+		if strings.HasPrefix(strings.TrimSpace(lineContent), token) {
 			return lineNumber
 		}
 	}
@@ -269,7 +269,7 @@ func (g *DockerfileGenerator) replaceTokens(ctx context.Context, lines []string)
 		return nil, fmt.Errorf("error generating Dockerfile content for mixins: %w", err)
 	}
 
-	fromToken := g.getIndexOfToken(lines, "FROM")
+	fromToken := g.getIndexOfToken(lines, "FROM") + 1
 
 	substitutions := []struct {
 		token        string

pkg/build/dockerfile-generator_test.go

@@ -103,6 +103,35 @@ COPY mybin /cnab/app/
 		require.NoError(t, err)
 		test.CompareGoldenFile(t, "testdata/custom-dockerfile-expected-output.Dockerfile", strings.Join(gotlines, "\n"))
 	})
+
+	t.Run("build from custom docker without PORTER_INIT supplied", func(t *testing.T) {
+		t.Parallel()
+
+		c := config.NewTestConfig(t)
+		tmpl := templates.NewTemplates(c.Config)
+		configTpl, err := tmpl.GetManifest()
+		require.Nil(t, err)
+		c.TestContext.AddTestFileContents(configTpl, config.Name)
+
+		m, err := manifest.LoadManifestFrom(context.Background(), c.Config, config.Name)
+		require.NoError(t, err, "could not load manifest")
+
+		// Use a custom dockerfile template
+		m.Dockerfile = "Dockerfile.template"
+		customFrom := `FROM ubuntu:latest
+# stuff
+COPY mybin /cnab/app/
+
+`
+		c.TestContext.AddTestFileContents([]byte(customFrom), "Dockerfile.template")
+
+		mp := mixin.NewTestMixinProvider()
+		g := NewDockerfileGenerator(c.Config, m, tmpl, mp)
+		gotlines, err := g.buildDockerfile(context.Background())
+
+		require.NoError(t, err)
+		test.CompareGoldenFile(t, "testdata/custom-dockerfile-without-init-expected-output.Dockerfile", strings.Join(gotlines, "\n"))
+	})
 }
 
 func TestPorter_generateDockerfile(t *testing.T) {

pkg/build/testdata/custom-dockerfile-without-init-expected-output.Dockerfile

@@ -0,0 +1,19 @@
+# syntax=docker/dockerfile-upstream:1.4.0
+FROM ubuntu:latest
+ARG BUNDLE_DIR
+ARG BUNDLE_UID=65532
+ARG BUNDLE_USER=nonroot
+ARG BUNDLE_GID=0
+RUN useradd ${BUNDLE_USER} -m -u ${BUNDLE_UID} -g ${BUNDLE_GID} -o
+# stuff
+COPY mybin /cnab/app/
+
+# exec mixin has no buildtime dependencies
+
+RUN rm ${BUNDLE_DIR}/porter.yaml
+RUN rm -fr ${BUNDLE_DIR}/.cnab
+COPY --link .cnab /cnab
+RUN chgrp -R ${BUNDLE_GID} /cnab && chmod -R g=u /cnab
+USER ${BUNDLE_UID}
+WORKDIR ${BUNDLE_DIR}
+CMD ["/cnab/app/run"]

pkg/build/testdata/missing-args-expected-output.Dockerfile

@@ -1,12 +1,12 @@
 # syntax=docker/dockerfile-upstream:1.4.0
 FROM ubuntu:latest
-COPY mybin /cnab/app/
-
 ARG BUNDLE_DIR
 ARG BUNDLE_UID=65532
 ARG BUNDLE_USER=nonroot
 ARG BUNDLE_GID=0
 RUN useradd ${BUNDLE_USER} -m -u ${BUNDLE_UID} -g ${BUNDLE_GID} -o
+COPY mybin /cnab/app/
+
 # exec mixin has no buildtime dependencies
 
 RUN rm ${BUNDLE_DIR}/porter.yaml

pkg/build/testdata/missing-mixins-token-expected-output.Dockerfile

@@ -1,12 +1,12 @@
 # syntax=docker/dockerfile-upstream:1.4.0
 FROM ubuntu:light
 ARG BUNDLE_DIR
-COPY mybin /cnab/app/
-ARG BUNDLE_DIR
 ARG BUNDLE_UID=65532
 ARG BUNDLE_USER=nonroot
 ARG BUNDLE_GID=0
 RUN useradd ${BUNDLE_USER} -m -u ${BUNDLE_UID} -g ${BUNDLE_GID} -o
+ARG BUNDLE_DIR
+COPY mybin /cnab/app/
 # exec mixin has no buildtime dependencies
 
 RUN rm ${BUNDLE_DIR}/porter.yaml