validate watch.path is set to a valid path

loader/loader.go

@@ -373,9 +373,10 @@ func loadYamlModel(ctx context.Context, config types.ConfigDetails, opts *Option
 
 	dict = groupXFieldsIntoExtensions(dict, tree.NewPath())
 
-	// TODO(ndeloof) shall we implement this as a Validate func on types ?
-	if err := validation.Validate(dict); err != nil {
-		return nil, err
+	if !opts.SkipValidation {
+		if err := validation.Validate(dict); err != nil {
+			return nil, err
+		}
 	}
 
 	if opts.ResolvePaths {

loader/loader_test.go

@@ -2750,6 +2750,7 @@ services:
           action: sync+restart
 `, nil), func(options *Options) {
 		options.ResolvePaths = false
+		options.SkipValidation = true
 	})
 	assert.NilError(t, err)
 	frontend, err := project.GetService("frontend")

paths/resolve.go

@@ -96,7 +96,10 @@ func (r *relativePathsResolver) absPath(value any) (any, error) {
 		if filepath.IsAbs(v) {
 			return v, nil
 		}
-		return filepath.Join(r.workingDir, v), nil
+		if v != "" {
+			return filepath.Join(r.workingDir, v), nil
+		}
+		return v, nil
 	}
 	return nil, fmt.Errorf("unexpected type %T", value)
 }

schema/compose-spec.json

@@ -461,6 +461,7 @@
               "target": {"type": "string"}
             }
           },
+          "required": ["path", "action"],
           "additionalProperties": false,
           "patternProperties": {"^x-": {}}
         }

validation/validation.go

@@ -18,17 +18,20 @@ package validation
 
 import (
 	"fmt"
+	"os"
 	"strings"
 
 	"github.com/compose-spec/compose-go/v2/tree"
+	"github.com/pkg/errors"
 )
 
 type checkerFunc func(value any, p tree.Path) error
 
 var checks = map[tree.Path]checkerFunc{
-	"volumes.*": checkVolume,
-	"configs.*": checkFileObject("file", "environment", "content"),
-	"secrets.*": checkFileObject("file", "environment"),
+	"volumes.*":                       checkVolume,
+	"configs.*":                       checkFileObject("file", "environment", "content"),
+	"secrets.*":                       checkFileObject("file", "environment"),
+	"services.*.develop.watch.*.path": checkPath,
 }
 
 func Validate(dict map[string]any) error {
@@ -85,3 +88,14 @@ func checkFileObject(keys ...string) checkerFunc {
 		return nil
 	}
 }
+
+func checkPath(value any, p tree.Path) error {
+	v := value.(string)
+	if v == "" {
+		return errors.Errorf("%s: value can't be blank", p)
+	}
+	if _, err := os.Stat(v); err != nil {
+		return errors.Wrapf(err, "%s: invalid path %s", p, value)
+	}
+	return nil
+}