Revert document detection on single file format as we lose most of the validation errors while detecting which part is what.

This is clearly not the right solution, so I prefer to revert and go back to the old behavior: fixed order.

Signed-off-by: Silvin Lubecki <silvin.lubecki@docker.com>

Author: silvin-lubecki

e2e/testdata/render/singlefile/my.dockerapp

@@ -1,3 +1,9 @@
+version: 0.1.0
+name: myapp
+maintainers:
+  - name: dev
+    email: dev@example.com
+---
 version: "3.4"
 services:
   test:
@@ -8,9 +14,3 @@ myapp:
   command1: cat
   command2: foo
   command3: bar
----
-version: 0.1.0
-name: myapp
-maintainers:
-  - name: dev
-    email: dev@example.com

loader/loader.go

@@ -8,10 +8,7 @@ import (
 	"path/filepath"
 
 	"github.com/docker/app/internal"
-	"github.com/docker/app/specification"
 	"github.com/docker/app/types"
-	"github.com/docker/cli/cli/compose/loader"
-	"github.com/docker/cli/cli/compose/schema"
 	"github.com/docker/docker/pkg/archive"
 	"github.com/pkg/errors"
 )
@@ -69,26 +66,12 @@ func LoadFromSingleFile(path string, r io.Reader, ops ...func(*types.App) error)
 		return nil, errors.Errorf("malformed single-file application: expected 3 documents, got %d", len(parts))
 	}
 
-	var (
-		metadata io.Reader
-		compose  io.Reader
-		params   io.Reader
-	)
-	for i := 0; i < 3; i++ {
-		parsed, err := loader.ParseYAML(parts[i])
-		if err != nil {
-			return nil, err
-		}
-		if err := specification.Validate(parsed, internal.MetadataVersion); metadata == nil && err == nil {
-			metadata = bytes.NewBuffer(parts[i])
-		} else if err2 := schema.Validate(parsed, schema.Version(parsed)); compose == nil && err2 == nil {
-			compose = bytes.NewBuffer(parts[i])
-		} else if params == nil {
-			params = bytes.NewBuffer(parts[i])
-		} else {
-			return nil, errors.New("malformed single-file application")
-		}
-	}
+	// 0. is metadata
+	metadata := bytes.NewBuffer(parts[0])
+	// 1. is compose
+	compose := bytes.NewBuffer(parts[1])
+	// 2. is parameters
+	params := bytes.NewBuffer(parts[2])
 
 	appOps := append([]func(*types.App) error{
 		types.WithComposes(compose),

loader/loader_test.go

@@ -46,10 +46,6 @@ func TestLoadFromSingleFile(t *testing.T) {
 			name: "mixed-carriage-return-line-feed",
 			file: fmt.Sprintf("%s\r\n---\r\n%s\r\n---\n%s", metadata, compose, params),
 		},
-		{
-			name: "unordered-documents",
-			file: fmt.Sprintf("%s\n---\n%s\n---\n%s", params, metadata, compose),
-		},
 	}
 	for _, test := range testCases {
 		t.Run(test.name, func(t *testing.T) {