Fixes bug when reading tile_name variable

Exposes the BakeArgumentsFromKilnfileConfiguration to be public for
easier testing - we know this may not be ideal, and are open to changes
that use the existing Bake tests

[#187167974](https://www.pivotaltracker.com/story/show/187167974)

Authored-by: Ryan Wittrup <rwittrup@vmware.com>

internal/commands/bake.go

@@ -437,7 +437,7 @@ func (b Bake) Execute(args []string) error {
 		// TODO remove when stemcell tarball is deprecated
 		stemcellManifest, err = b.stemcell.FromTarball(b.Options.StemcellTarball)
 	} else if b.Options.Kilnfile != "" {
-		if err := bakeArgumentsFromKilnfileConfiguration(&b.Options, templateVariables); err != nil {
+		if err := BakeArgumentsFromKilnfileConfiguration(&b.Options, templateVariables); err != nil {
 			return fmt.Errorf("failed to parse releases: %s", err)
 		}
 		templateVariables, err = b.templateVariables.FromPathsAndPairs(b.Options.VariableFiles, b.Options.Variables)
@@ -590,7 +590,7 @@ func (b Bake) Usage() jhanda.Usage {
 	}
 }
 
-func bakeArgumentsFromKilnfileConfiguration(options *BakeOptions, variables map[string]any) error {
+func BakeArgumentsFromKilnfileConfiguration(options *BakeOptions, variables map[string]any) error {
 	if options.Kilnfile == "" {
 		return nil
 	}
@@ -610,7 +610,7 @@ func bakeArgumentsFromKilnfileConfiguration(options *BakeOptions, variables map[
 	}
 	if tileName, ok := variables[builder.TileNameVariable]; ok {
 		name, ok := tileName.(string)
-		if ok {
+		if !ok {
 			return fmt.Errorf("%s value must be a string got value %#[2]v with type %[2]T", builder.TileNameVariable, tileName)
 		}
 		if index := slices.IndexFunc(kf.BakeConfigurations, func(configuration cargo.BakeConfiguration) bool {

internal/commands/bake_test.go

@@ -20,6 +20,7 @@ import (
 	"github.com/pivotal-cf/kiln/internal/builder"
 	"github.com/pivotal-cf/kiln/internal/commands"
 	"github.com/pivotal-cf/kiln/internal/commands/fakes"
+	"github.com/pivotal-cf/kiln/internal/commands/flags"
 	"github.com/pivotal-cf/kiln/pkg/proofing"
 	"github.com/pivotal-cf/kiln/pkg/source"
 )
@@ -940,6 +941,77 @@ var _ = Describe("Bake", func() {
 	})
 })
 
+var _ = Describe("BakeArgumentsFromKilnfileConfiguration", func() {
+	It("handles empty options and variables", func() {
+		opts := &commands.BakeOptions{}
+		variables := map[string]any{}
+
+		err := commands.BakeArgumentsFromKilnfileConfiguration(opts, variables)
+		Expect(err).NotTo(HaveOccurred())
+	})
+
+	It("handles a Kilnfile that does not exist", func() {
+		opts := &commands.BakeOptions{
+			Standard: flags.Standard{
+				Kilnfile: "/does/not/exist",
+			},
+		}
+		variables := map[string]any{}
+
+		err := commands.BakeArgumentsFromKilnfileConfiguration(opts, variables)
+		Expect(err).NotTo(HaveOccurred())
+	})
+
+	const validKilnfile = `---
+release_sources:
+  - type: s3
+    compiled: true
+    bucket: bucket
+    region: region
+    access_key_id: access_key_id
+    secret_access_key: secret_access_key
+    path_template: path_template
+`
+	When("passing a valid Kilnfile", func() {
+		var opts *commands.BakeOptions
+
+		BeforeEach(func() {
+			tempDir, err := os.MkdirTemp("", "bake_")
+			Expect(err).NotTo(HaveOccurred())
+
+			path := filepath.Join(tempDir, "Kilnfile")
+			Expect(os.WriteFile(path, []byte(validKilnfile), 0o644)).ToNot(HaveOccurred())
+
+			opts = &commands.BakeOptions{
+				Standard: flags.Standard{
+					Kilnfile: path,
+				},
+			}
+		})
+
+		It("handles empty variables", func() {
+			variables := map[string]any{}
+
+			err := commands.BakeArgumentsFromKilnfileConfiguration(opts, variables)
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		It("handles a valid tile_name variable", func() {
+			variables := map[string]any{"tile_name": "SRT"}
+
+			err := commands.BakeArgumentsFromKilnfileConfiguration(opts, variables)
+			Expect(err).NotTo(HaveOccurred())
+		})
+
+		It("returns an error for unexpected tile_name type", func() {
+			variables := map[string]any{"tile_name": 8675309}
+
+			err := commands.BakeArgumentsFromKilnfileConfiguration(opts, variables)
+			Expect(err).To(MatchError("tile_name value must be a string got value 8675309 with type int"))
+		})
+	})
+})
+
 type fakeWriteBakeRecordFunc struct {
 	tilePath, recordPath string
 	productTemplate      []byte