Added StaticJsonRpcProvider for reducing calls to chainId in certain …

…cases (#901).

packages/providers/src.ts/index.ts

@@ -26,9 +26,9 @@ import { IpcProvider } from "./ipc-provider";
 import { InfuraProvider } from "./infura-provider";
 import { JsonRpcProvider, JsonRpcSigner } from "./json-rpc-provider";
 import { NodesmithProvider } from "./nodesmith-provider";
+import { StaticJsonRpcProvider, UrlJsonRpcProvider } from "./url-json-rpc-provider";
 import { Web3Provider } from "./web3-provider";
 import { WebSocketProvider } from "./websocket-provider";
-
 import { ExternalProvider, JsonRpcFetchFunc } from "./web3-provider";
 
 import { Formatter } from "./formatter";
@@ -93,6 +93,7 @@ export {
     Provider,
     BaseProvider,
 
+    UrlJsonRpcProvider,
 
     ///////////////////////
     // Concreate Providers
@@ -105,6 +106,7 @@ export {
     InfuraProvider,
     JsonRpcProvider,
     NodesmithProvider,
+    StaticJsonRpcProvider,
     Web3Provider,
     WebSocketProvider,
 

packages/providers/src.ts/url-json-rpc-provider.ts

@@ -13,7 +13,26 @@ import { JsonRpcProvider, JsonRpcSigner } from "./json-rpc-provider";
 
 type getUrlFunc = (network: Network, apiKey: string) => string | ConnectionInfo;
 
-export abstract class UrlJsonRpcProvider extends JsonRpcProvider {
+// A StaticJsonRpcProvider is useful when you *know* for certain that
+// the backend will never change, as it never calls eth_chainId to
+// verify its backend. However, if the backend does change, the effects
+// are undefined and may include:
+// - inconsistent results
+// - locking up the UI
+// - block skew warnings
+// - wrong results
+export class StaticJsonRpcProvider extends JsonRpcProvider {
+    async detectNetwork(): Promise<Network> {
+        let network = this.network;
+        if (network == null) {
+            // After this call completes, network is defined
+            network = await super._ready();
+        }
+        return network;
+    }
+}
+
+export abstract class UrlJsonRpcProvider extends StaticJsonRpcProvider {
     readonly apiKey: any;
 
     constructor(network?: Networkish, apiKey?: any) {
@@ -36,10 +55,6 @@ export abstract class UrlJsonRpcProvider extends JsonRpcProvider {
         }
     }
 
-    async detectNetwork(): Promise<Network> {
-        return this.network;
-    }
-
     _startPending(): void {
         logger.warn("WARNING: API provider does not support pending filters");
     }