client: remove implicit call to Build on Deploy

client.go

@@ -33,6 +33,9 @@ type Client struct {
 	progressListener ProgressListener // progress listener
 }
 
+// ErrNotBuilt indicates the Function has not yet been built.
+var ErrNotBuilt = errors.New("not built")
+
 // Builder of Function source to runnable image.
 type Builder interface {
 	// Build a Function project with source located at path.
@@ -406,9 +409,10 @@ func (c *Client) Deploy(path string) (err error) {
 		return
 	}
 
-	// Build the Function
-	if err = c.Build(f.Root); err != nil {
-		return
+	// Functions must be built (have an associated image) before being deployed.
+	// Note that externally built images may be specified in the func.yaml
+	if !f.Built() {
+		return ErrNotBuilt
 	}
 
 	// Push the image for the named service to the configured registry

client_test.go

@@ -674,6 +674,36 @@ func TestListOutsideRoot(t *testing.T) {
 	}
 }
 
+// TestDeployUnbuilt ensures that a call to deploy a Function which was not
+// fully created (ie. was only initialized, not actually built and deploys)
+// yields an expected, and informative, error.
+func TestDeployUnbuilt(t *testing.T) {
+	root := "testdata/example.com/testDeploy" // Root from which to run the test
+	if err := os.MkdirAll(root, 0700); err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(root)
+
+	// New Client
+	client := bosonFunc.New(bosonFunc.WithRegistry(TestRegistry))
+
+	// Initialize (half-create) a new Function at root
+	if err := client.Create(bosonFunc.Function{Root: root}); err != nil {
+		t.Fatal(err)
+	}
+
+	// Now try to deploy it.  Ie. without having run the necessary build step.
+	err := client.Deploy(root)
+	if err == nil {
+		t.Fatal("did not receive an error attempting to deploy an unbuilt Function")
+	}
+
+	if !errors.Is(err, bosonFunc.ErrNotBuilt) {
+		t.Fatalf("did not receive expected error type.  Expected ErrNotBuilt, got %T", err)
+	}
+
+}
+
 // TODO: The tests which confirm an error is generated do not currently test
 // that the expected error is received; just that any error is generated.
 // This should be replaced with typed errors or at a minimum code prefixes