Validate parameters against the actual compose file

e2e/testdata/invalid/unused_parameter.dockerapp/docker-compose.yml

@@ -0,0 +1,29 @@
+version: "3.6"
+services:
+  api:
+    image: python:3.6
+    networks:
+      back:
+      front:
+        aliases:
+          - api.example.com
+          - ${api.host}
+  web:
+    image: nginx:latest
+    networks:
+      - front
+    volumes:
+      - static:/opt/${static_subdir}
+    ports:
+      - ${web.port}:80
+  db:
+    image: postgres:9.3
+    networks:
+      - back
+networks:
+  front:
+  back:
+volumes:
+  static:
+    external: true
+    name: corp/web-static-data

e2e/testdata/invalid/unused_parameter.dockerapp/metadata.yml

@@ -0,0 +1,8 @@
+version: 1.1.0-beta1
+name: simple
+description: "new fancy webapp with microservices"
+maintainers:
+  - name: John Developer
+    email: [email protected]
+  - name: Jane Developer
+    email: [email protected]

e2e/testdata/invalid/unused_parameter.dockerapp/parameters.yml

@@ -0,0 +1,7 @@
+web:
+  port: '8082'
+api:
+  host: example.com
+static_subdir: data/static
+unused:
+  parameter: FOO

e2e/validate_test.go

@@ -0,0 +1,20 @@
+package e2e
+
+import (
+	"path"
+	"strings"
+	"testing"
+
+	"gotest.tools/assert"
+
+	"gotest.tools/icmd"
+)
+
+func TestOrphanedParameter(t *testing.T) {
+	cmd, cleanup := dockerCli.createTestCmd()
+	defer cleanup()
+	p := path.Join("testdata", "invalid", "unused_parameter")
+	cmd.Command = dockerCli.Command("app", "validate", p)
+	out := icmd.RunCmd(cmd).Assert(t, icmd.Expected{ExitCode: 1}).Combined()
+	assert.Assert(t, strings.Contains(out, "unused.parameter is declared as parameter but not used by the compose file"))
+}

internal/commands/validate.go

@@ -4,11 +4,13 @@ import (
 	"fmt"
 	"os"
 
+	"github.com/docker/app/internal/compose"
 	"github.com/docker/app/internal/packager"
 	"github.com/docker/app/render"
 	"github.com/docker/app/types"
 	"github.com/docker/cli/cli"
 	cliopts "github.com/docker/cli/opts"
+	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 )
 
@@ -23,22 +25,37 @@ func validateCmd() *cobra.Command {
 		Short: "Checks the rendered application is syntactically correct",
 		Args:  cli.RequiresMaxArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			app, err := packager.Extract(firstOrEmpty(args),
-				types.WithParametersFiles(opts.parametersFiles...),
-			)
-			if err != nil {
-				return err
-			}
-			defer app.Cleanup()
-			argParameters := cliopts.ConvertKVStringsToMap(opts.overrides)
-			_, err = render.Render(app, argParameters, nil)
-			if err != nil {
-				return err
-			}
-			fmt.Fprintf(os.Stdout, "Validated %q\n", app.Path)
-			return nil
+			return runValidate(args, opts)
 		},
 	}
 	opts.parametersOptions.addFlags(cmd.Flags())
 	return cmd
 }
+
+func runValidate(args []string, opts validateOptions) error {
+	app, err := packager.Extract(firstOrEmpty(args),
+		types.WithParametersFiles(opts.parametersFiles...),
+	)
+	if err != nil {
+		return err
+	}
+	defer app.Cleanup()
+	argParameters := cliopts.ConvertKVStringsToMap(opts.overrides)
+	_, err = render.Render(app, argParameters, nil)
+	if err != nil {
+		return err
+	}
+
+	vars, err := compose.ExtractVariables(app.Composes()[0], compose.ExtrapolationPattern)
+	if err != nil {
+		return errors.Wrap(err, "failed to parse compose file")
+	}
+	for k := range app.Parameters().Flatten() {
+		if _, ok := vars[k]; !ok {
+			return fmt.Errorf("%s is declared as parameter but not used by the compose file", k)
+		}
+	}
+
+	fmt.Fprintf(os.Stdout, "Validated %q\n", app.Path)
+	return nil
+}