limit min layer length in manifest to one

Signed-off-by: xiekeyang <[email protected]>

Author: xiekeyang

schema/fs.go

@@ -205,7 +205,7 @@ var _escData = map[string]*_escFile{
 	"/config-schema.json": {
 		local:   "config-schema.json",
 		size:    774,
-		modtime: 1478292182,
+		modtime: 1478076438,
 		compressed: `
 H4sIAAAJbogA/5SRvW7rMAyFdz+F4WS8ju7QKWsfoEPHooMqUzEDWFRJZgiKvHv1EzcxEBTuEsSH/M4R
 ya+mbbsBxDFGRQrdvu1eIoRnCmoxALfpn8dD+xrBoUdnS9e/jG3FjTDZjIyqcW/MUSj0Vd0RH8zA1mv/
@@ -219,7 +219,7 @@ AP//XlvgsQYDAAA=
 	"/content-descriptor.json": {
 		local:   "content-descriptor.json",
 		size:    836,
-		modtime: 1479340044,
+		modtime: 1479375772,
 		compressed: `
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 5j173zKA3GIomToh7/It5Pcduv/eiSGHDPoPncDdaPIMDx2WVFFpBuKPjliGssHWKN6IdNui2AfvVkld
@@ -234,7 +234,7 @@ DLQ9RAMAAA==
 	"/defs-config.json": {
 		local:   "defs-config.json",
 		size:    2270,
-		modtime: 1478292182,
+		modtime: 1478076438,
 		compressed: `
 H4sIAAAJbogA/+RVzY7TMBC+5yksw7GwF8SB6y5HVKQKOCBUucl4O0vsMeMJEKF9d5xs6cZJG7q79MSh
 ajLx9zMz9vhXoZSuIJaMQZC8fqP0FVj02L1FFQwLlk1tWAmpZQB/SV4MemCVnixeq1WAEi2Wpscv7gj3
@@ -250,7 +250,7 @@ OU9Ck3MwHdKnQMEFadd9J4/BN0Q1GH/0PBTd77b4HQAA//9fxiKD3ggAAA==
 	"/defs-image.json": {
 		local:   "defs-image.json",
 		size:    2781,
-		modtime: 1479340044,
+		modtime: 1479375772,
 		compressed: `
 H4sIAAAJbogA/7SWS0/cMBDH7/sprIDEYR/poarUFUKqyqUnKtFT0bYanMlmaGKnthe6oP3utfN0XqAt
 9AQe23//f+MZZ59mjAURaq4oNyRFsGbBJcYkyI00y0EZ4rsUFDOSXeUoPkthgAQq9iWDLbLrHDnFxKHY
@@ -270,7 +270,7 @@ LqRf/TaNIdU4m8qJ92LN/L/1rwEQQhro/iQ7ugR8keYDLAVexZ2nafRjMvFxyiC/LvJy3cuOl5ensYdS
 	"/defs.json": {
 		local:   "defs.json",
 		size:    3193,
-		modtime: 1478292182,
+		modtime: 1471577655,
 		compressed: `
 H4sIAAAJbogA/7RWTXPaMBC98ys8tEfa2PIX9NYp/cghAzOZnjo9uGYBtSCpstxpmuG/VzLGWPZiMKWH
 JPau9r23T6tYzwPHGS4gSyUVinI2fOMMp7CkjJq3zMkzWDhqLXm+WvNc6UdwZgLYO85UQhlI51FASpc0
@@ -288,23 +288,24 @@ MrVJbn8cB+ZnN/gbAAD//0JyEpx5DAAA
 
 	"/image-manifest-schema.json": {
 		local:   "image-manifest-schema.json",
-		size:    1118,
-		modtime: 1479340044,
+		size:    1139,
+		modtime: 1479462889,
 		compressed: `
-H4sIAAAJbogA/6RSO4/UMBDu8ytGvuu4xICorqWiQBScaBCFiSfJnOIHtm/F6rT/HT/iTbJLgdgyX/y9
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-xMG3ZaAp1B2PQLyT/HrHbGrWnJQ5/PVCDuV5W+xv58gud1/3sR9vk7Z2av4EAAD//wnPEwleBAAA
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+pJlzBAAA
 `,
 	},
 
 	"/manifest-list-schema.json": {
 		local:   "manifest-list-schema.json",
 		size:    1101,
-		modtime: 1479340044,
+		modtime: 1479462884,
 		compressed: `
 H4sIAAAJbogA/6ySP48TMRDF+3yKkY8OsgZEdS00SCAKTjSIwqxnd+cU/8Hjizid8t3xn/Vml1AgXZpI
 eet57/fsedoBCI3cB/KRnBW3IL54tO+djYosBvho1IjwWVkakCN8ovTz1WNPA/WqjLzKHi+4n9CoPD/F

schema/image-manifest-schema.json

@@ -23,6 +23,7 @@
     },
     "layers": {
       "type": "array",
+      "minItems": 1,
       "items": {
         "$ref": "content-descriptor.json"
       }

schema/manifest_test.go

@@ -125,6 +125,23 @@ func TestManifest(t *testing.T) {
 `,
 			fail: false,
 		},
+
+		// expected failure: empty layer, expected at least one
+		{
+			manifest: `
+{
+  "schemaVersion": 2,
+  "mediaType": "application/vnd.oci.image.manifest.v1+json",
+  "config": {
+    "mediaType": "application/vnd.oci.image.config.v1+json",
+    "size": 1470,
+    "digest": "sha256:c86f7763873b6c0aae22d963bab59b4f5debbed6685761b5951584f6efb0633b"
+  },
+  "layers": []
+}
+`,
+			fail: true,
+		},
 	} {
 		r := strings.NewReader(tt.manifest)
 		err := schema.MediaTypeManifest.Validate(r)