Retry etherscan calls (#86)

Author: krzkaczor

packages/ethereum-viewer/package.json

@@ -16,6 +16,7 @@
   },
   "dependencies": {
     "fast-json-stable-stringify": "^2.1.0",
+    "fetch-retry": "^5.0.6",
     "match-sorter": "^6.3.1",
     "p-finally": "^2.0.1",
     "path-browserify": "^1.0.1",

packages/ethereum-viewer/src/explorer/fetchFiles.ts

@@ -2,12 +2,20 @@ import { join } from "path";
 import { assert, StrictOmit } from "ts-essentials";
 
 import { fetch as _fetch } from "../util/fetch";
+import { makeSolidFetch } from "../util/solidFetch";
 import { prettyStringify } from "../util/stringify";
 import * as types from "./api-types";
 import { apiUrlToWebsite } from "./apiUrlToWebsite";
 import { fileExtension } from "./fileExtension";
 import { ApiName, explorerApiKeys, explorerApiUrls } from "./networks";
 
+const fetchEtherscanResponse = makeSolidFetch({
+  async verifyResponse(response: unknown): Promise<boolean> {
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+    return (response as any)?.message === "OK" || false;
+  },
+});
+
 interface FetchFilesOptions {
   /**
    * For unit testing.
@@ -27,7 +35,11 @@ interface FetchFilesOptions {
 export async function fetchFiles(
   apiName: ApiName,
   contractAddress: string,
-  { fetch = _fetch, proxyDepth = 3, skipPrefix = false }: FetchFilesOptions = {}
+  {
+    fetch = fetchEtherscanResponse,
+    proxyDepth = 3,
+    skipPrefix = false,
+  }: FetchFilesOptions = {}
 ): Promise<FetchFilesResult> {
   const apiUrl = explorerApiUrls[apiName];
   const url =

packages/ethereum-viewer/src/openContractSource.ts

@@ -118,6 +118,7 @@ async function saveSingleContractFilesToFs(
   return {
     entries,
     mainFile: withPrefix(mainFile),
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
     contractName: result.info.ContractName ?? "contract",
   };
 }
@@ -133,7 +134,7 @@ function getMainContractFile(
 
   if (!fileToShow) {
     const regexp = new RegExp(`contract\\s+${name}`);
-    fileToShow = files.find(([path, source]) => regexp.test(source));
+    fileToShow = files.find(([_path, source]) => regexp.test(source));
   }
 
   if (!fileToShow) fileToShow = files.sort(byPathLength)[0];

packages/ethereum-viewer/src/util/solidFetch.ts

@@ -0,0 +1,45 @@
+import fetchRetry from "fetch-retry";
+
+interface MakeSolidFetchOptions {
+  /**
+   * return false if the response should be retried
+   */
+  verifyResponse: (response: unknown) => Promise<boolean>;
+}
+
+// @note: returns already parsed response
+type SolidFetch = (input: string, init?: RequestInit) => Promise<unknown>;
+
+export function makeSolidFetch(opts: MakeSolidFetchOptions): SolidFetch {
+  const solidFetch = fetchRetry(self.fetch, {
+    retries: 3,
+    async retryOn(_attempt, error, response) {
+      const retry = error !== null || !response?.ok;
+      if (retry) {
+        // eslint-disable-next-line no-console
+        console.log("Retrying failed fetch", {
+          error,
+          status: response?.status,
+        });
+      }
+      // if we have a response, we verify it and decide if we should retry
+      if (!retry) {
+        const responseJson = await response.clone().json();
+        const verified = await opts.verifyResponse(responseJson);
+        if (!verified) {
+          console.log("Response verification failed, retrying...");
+        }
+
+        return !verified;
+      }
+
+      return true;
+    },
+    retryDelay: function (attempt) {
+      return Math.pow(2, attempt) * 1000;
+    },
+  });
+
+  return (input: string, init?: RequestInit) =>
+    solidFetch(input, init).then((response) => response.json());
+}