Allow 'none' as value for explorer standard

src/main/kotlin/org/ethereum/lists/chains/Main.kt

@@ -191,8 +191,8 @@ fun checkChain(chainFile: File, connectRPC: Boolean) {
                 throw(ExplorerInvalidUrl())
             }
 
-            if (explorer["standard"] != "EIP3091") {
+            if (explorer["standard"] != "EIP3091" && explorer["standard"] != "none") {
-                throw(ExplorerStandardMustBeEIP3091())
+                throw(ExplorerStandardMustBeEIP3091OrNone())
             }
         }
     }

src/main/kotlin/org/ethereum/lists/chains/model/Exceptions.kt

@@ -15,7 +15,7 @@ class UnsupportedNamespace(): Exception("So far only the EIP155 namespace is sup
 class ExplorersMustBeArray: Exception("explorers must be an array")
 class ExplorerMustHaveName: Exception("Explorer must have name")
 class ExplorerInvalidUrl: Exception("Explorer have url starting with https://")
-class ExplorerStandardMustBeEIP3091: Exception("explorer standard must be EIP3091 - currently the only one supported")
+class ExplorerStandardMustBeEIP3091OrNone: Exception("explorer standard must be 'none' or 'EIP3091'")
 class ParentHasInvalidType(type: String?): Exception("Parent has invalid type $type - only L2 or shard allowed")
 class ParentMustBeObject: Exception("parent must be an object")
 class ParentMustHaveChainAndType: Exception("parent must have fields 'chain' and 'type'")

src/test/kotlin/org/ethereum/lists/chains/TheChainChecker.kt

@@ -28,6 +28,14 @@ class TheChainChecker {
         checkChain(file, false)
     }
 
+    @Test
+    fun shouldPassForValidChainWithExplorersNoStandard() {
+        val file = getFile("valid/withexplorer/eip155-2.json")
+
+        checkChain(file, false)
+    }
+
+
     @Test
     fun shouldPassForValidChainWithParent() {
         val file = getFile("valid/withparent/eip155-2.json")
@@ -186,7 +194,7 @@ class TheChainChecker {
         checkChain(getFile("invalid/explorersnotarray/eip155-1.json"), false)
     }
 
-    @Test(expected = ExplorerStandardMustBeEIP3091::class)
+    @Test(expected = ExplorerStandardMustBeEIP3091OrNone::class)
     fun shouldFailOnWrongExplorerStandard() {
         checkChain(getFile("invalid/wrongexplorerstandard/eip155-1.json"), false)
     }

src/test/resources/test_chains/valid/withexplorer/eip155-2.json

@@ -0,0 +1,26 @@
+{
+  "name": "Ethereum Mainnet",
+  "shortName": "eth",
+  "chain": "ETH",
+  "network": "mainnet",
+  "chainId": 2,
+  "networkId": 2,
+  "rpc": [
+    "https://mainnet.infura.io/v3/${INFURA_API_KEY}",
+    "https://api.mycryptoapi.com/eth"
+  ],
+  "faucets": [],
+  "infoURL": "https://ethereum.org",
+  "nativeCurrency": {
+    "name": "Ether",
+    "symbol": "ETH",
+    "decimals": 18
+  },
+  "explorers": [
+    {
+      "name": "some",
+      "url": "https://etherscan.io",
+      "standard": "none"
+    }
+  ]
+}