Better provider internal block management (#1084, #1208, #1221, #1235).

packages/providers/src.ts/base-provider.ts

@@ -585,20 +585,35 @@ export class BaseProvider extends Provider implements EnsProvider {
     async _getInternalBlockNumber(maxAge: number): Promise<number> {
         await this._ready();
 
-        const internalBlockNumber = this._internalBlockNumber;
+        // Allowing stale data up to maxAge old
+        if (maxAge > 0) {
 
-        if (maxAge > 0 && internalBlockNumber) {
-            try {
-                const result = await internalBlockNumber;
-                if ((getTime() - result.respTime) <= maxAge) {
-                    return result.blockNumber;
-                }
-            } catch(error) {
-                // Don't null the dead (rejected) fetch, if it has already been updated
-                if (this._internalBlockNumber === internalBlockNumber) {
-                    this._internalBlockNumber = null;
+            // While there are pending internal block requests...
+            while (this._internalBlockNumber) {
+
+                // ..."remember" which fetch we started with
+                const internalBlockNumber = this._internalBlockNumber;
+
+                try {
+                    // Check the result is not too stale
+                    const result = await internalBlockNumber;
+                    if ((getTime() - result.respTime) <= maxAge) {
+                        return result.blockNumber;
+                    }
+
+                    // Too old; fetch a new value
+                    break;
+
+                } catch(error) {
+
+                    // The fetch rejected; if we are the first to get the
+                    // rejection, drop through so we replace it with a new
+                    // fetch; all others blocked will then get that fetch
+                    // which won't match the one they "remembered" and loop
+                    if (this._internalBlockNumber === internalBlockNumber) {
+                        break;
+                    }
                 }
-                throw error;
             }
         }