resolveRelativePaths can run with non-canonical model

Signed-off-by: Nicolas De Loof <[email protected]>

loader/extends.go

@@ -190,7 +190,7 @@ func getExtendsBaseFromFile(
 			)
 		}
 
-		// Attempt to make a canonical model so ResolveRelativePaths can operate on source:target short syntaxes
+		// Attempt to make a canonical model so ResolveRelativePaths can operate on source:target short syntax
 		source, err = transform.Canonical(source, true)
 		if err != nil {
 			return nil, nil, err

loader/extends_test.go

@@ -484,3 +484,20 @@ services:
 	assert.NilError(t, err)
 	assert.Check(t, p.Services["test"].Command == nil)
 }
+
+func TestExtendsWithInterpolation(t *testing.T) {
+	yaml := `
+name: test-extends-with-interpolation
+services:
+  test:
+    extends: { file: testdata/extends/interpolated.yaml, service: foo }
+`
+	p, err := Load(types.ConfigDetails{
+		ConfigFiles: []types.ConfigFile{{
+			Content:  []byte(yaml),
+			Filename: "-",
+		}},
+	})
+	assert.NilError(t, err)
+	assert.Check(t, p.Services["test"].Volumes[0].Source == "/dev/null")
+}

loader/testdata/extends/interpolated.yaml

@@ -0,0 +1,5 @@
+services:
+  foo:
+    image: bash
+    volumes:
+      - ${SOURCE:-/dev/null}:/tmp/foo:ro

paths/resolve.go

@@ -116,24 +116,30 @@ func (r *relativePathsResolver) absPath(value any) (any, error) {
 		}
 		return v, nil
 	}
+
 	return nil, fmt.Errorf("unexpected type %T", value)
 }
 
 func (r *relativePathsResolver) absVolumeMount(a any) (any, error) {
-	vol := a.(map[string]any)
-	if vol["type"] != types.VolumeTypeBind {
+	switch vol := a.(type) {
+	case map[string]any:
+		if vol["type"] != types.VolumeTypeBind {
+			return vol, nil
+		}
+		src, ok := vol["source"]
+		if !ok {
+			return nil, errors.New(`invalid mount config for type "bind": field Source must not be empty`)
+		}
+		abs, err := r.maybeUnixPath(src.(string))
+		if err != nil {
+			return nil, err
+		}
+		vol["source"] = abs
 		return vol, nil
+	default:
+		// not using canonical format, skip
+		return a, nil
 	}
-	src, ok := vol["source"]
-	if !ok {
-		return nil, errors.New(`invalid mount config for type "bind": field Source must not be empty`)
-	}
-	abs, err := r.maybeUnixPath(src.(string))
-	if err != nil {
-		return nil, err
-	}
-	vol["source"] = abs
-	return vol, nil
 }
 
 func (r *relativePathsResolver) volumeDriverOpts(a any) (any, error) {