Add support for valueFrom property (similar to app.yaml) inside Apps config field in bundle configuration (#4297)

## Changes
Add support for valueFrom property (similar to app.yaml) inside Apps
config field in bundle configuration

## Why
Fixes #4288

## Tests
Added a unit test

<!-- If your PR needs to be included in the release notes for next
release,
add a separate entry in NEXT_CHANGELOG.md as part of your PR. -->

Author: andrewnester

NEXT_CHANGELOG.md

@@ -7,6 +7,7 @@
 ### CLI
 
 ### Bundles
+* Add support for valueFrom property (similar to app.yaml) inside Apps config field in bundle configuration ([#4297](https://github.com/databricks/cli/pull/4297))
 * engine/direct: Support bind & unbind. ([#4279](https://github.com/databricks/cli/pull/4279))
 
 ### Dependency updates

acceptance/bundle/refschema/out.fields.txt

@@ -106,6 +106,7 @@ resources.apps.*.config.env	[]resources.AppEnvVar	INPUT
 resources.apps.*.config.env[*]	resources.AppEnvVar	INPUT
 resources.apps.*.config.env[*].name	string	INPUT
 resources.apps.*.config.env[*].value	string	INPUT
+resources.apps.*.config.env[*].value_from	string	INPUT
 resources.apps.*.create_time	string	ALL
 resources.apps.*.creator	string	ALL
 resources.apps.*.default_source_code_path	string	ALL

bundle/config/resources/apps.go

@@ -26,7 +26,10 @@ type AppEnvVar struct {
 	Name string `json:"name" yaml:"name"`
 
 	// Value is the environment variable value
-	Value string `json:"value" yaml:"value"`
+	Value string `json:"value,omitempty" yaml:"value,omitempty"`
+
+	// ValueFrom is the name of an external Databricks resource that contains the value, such as a secret or a database table.
+	ValueFrom string `json:"value_from,omitempty" yaml:"value_from,omitempty"`
 }
 
 type App struct {

bundle/internal/schema/annotations.yml

@@ -515,6 +515,9 @@ github.com/databricks/cli/bundle/config/resources.AppEnvVar:
   "value":
     "description": |-
       PLACEHOLDER
+  "value_from":
+    "description": |-
+      PLACEHOLDER
 github.com/databricks/cli/bundle/config/resources.AppPermission:
   "group_name":
     "description": |-

bundle/internal/validation/generated/required_fields.go

@@ -176,8 +176,9 @@ func (a *appRunner) buildAppDeployment() apps.AppDeployment {
 			deployment.EnvVars = make([]apps.EnvVar, len(a.app.Config.Env))
 			for i, env := range a.app.Config.Env {
 				deployment.EnvVars[i] = apps.EnvVar{
-					Name:  env.Name,
-					Value: env.Value,
+					Name:      env.Name,
+					Value:     env.Value,
+					ValueFrom: env.ValueFrom,
 				}
 			}
 		}

bundle/run/app.go

@@ -270,3 +270,56 @@ func TestStopApp(t *testing.T) {
 	err := r.Cancel(ctx)
 	require.NoError(t, err)
 }
+
+func TestBuildAppDeploymentWithValueFrom(t *testing.T) {
+	app := &resources.App{
+		SourceCodePath: "/path/to/app",
+		Config: &resources.AppConfig{
+			Command: []string{"python", "app.py"},
+			Env: []resources.AppEnvVar{
+				{
+					Name:  "REGULAR_VAR",
+					Value: "regular_value",
+				},
+				{
+					Name:      "SECRET_VAR",
+					ValueFrom: "secrets/my-secret",
+				},
+				{
+					Name:      "COMBINED_VAR",
+					Value:     "default_value",
+					ValueFrom: "secrets/override",
+				},
+			},
+		},
+	}
+
+	runner := &appRunner{
+		app: app,
+	}
+
+	deployment := runner.buildAppDeployment()
+
+	require.Equal(t, apps.AppDeploymentModeSnapshot, deployment.Mode)
+	require.Equal(t, "/path/to/app", deployment.SourceCodePath)
+	require.Len(t, deployment.Command, 2)
+	require.Equal(t, "python", deployment.Command[0])
+	require.Equal(t, "app.py", deployment.Command[1])
+
+	require.Len(t, deployment.EnvVars, 3)
+
+	// Regular env var with value
+	require.Equal(t, "REGULAR_VAR", deployment.EnvVars[0].Name)
+	require.Equal(t, "regular_value", deployment.EnvVars[0].Value)
+	require.Equal(t, "", deployment.EnvVars[0].ValueFrom)
+
+	// Env var with value_from
+	require.Equal(t, "SECRET_VAR", deployment.EnvVars[1].Name)
+	require.Equal(t, "", deployment.EnvVars[1].Value)
+	require.Equal(t, "secrets/my-secret", deployment.EnvVars[1].ValueFrom)
+
+	// Env var with both value and value_from
+	require.Equal(t, "COMBINED_VAR", deployment.EnvVars[2].Name)
+	require.Equal(t, "default_value", deployment.EnvVars[2].Value)
+	require.Equal(t, "secrets/override", deployment.EnvVars[2].ValueFrom)
+}