Don't assume that we're getting back JSON from anyone (#145)

- Imbibe API requests as text, and wrap the JSON parsing in try blocks
- Remove trailing slashes from transfer urls

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## In master
 
+- When parsing API responses, take extra care making sure that the responses are
+  valid JSON, and throw if not.
 - [KeyManager] Correctly handle non-successful HTTP status codes when fetching
   auth tokens.
 - [Transfers] Correctly handle non-successful HTTP status codes for

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@stellar/wallet-sdk",
-  "version": "0.0.9-rc.3",
+  "version": "0.0.9-rc.4",
   "description": "Libraries to help you write Stellar-enabled wallets in Javascript",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

src/KeyManager.ts

@@ -325,11 +325,21 @@ export class KeyManager {
 
     const keyNetwork = key.network || this.defaultNetworkPassphrase;
 
-    const {
-      transaction,
-      network_passphrase,
-      error,
-    } = await challengeRes.json();
+    const text = await challengeRes.text();
+
+    let transaction;
+    let network_passphrase;
+    let error;
+
+    try {
+      const json = JSON.parse(text);
+
+      transaction = json.transaction;
+      network_passphrase = json.network_passphrase;
+      error = json.error;
+    } catch (e) {
+      throw new Error(`Request for challenge returned invalid JSON: ${text}`);
+    }
 
     if (error) {
       throw new Error(error);

src/transfers/TransferProvider.ts

@@ -99,7 +99,8 @@ export abstract class TransferProvider {
       throw new Error("Required parameter `operation` missing!");
     }
 
-    this.transferServer = transferServer;
+    // remove the trailing /
+    this.transferServer = transferServer.replace(/\/$/, "");
     this.operation = operation;
     this.account = account;
 
@@ -127,10 +128,20 @@ export abstract class TransferProvider {
       }
     }
 
-    const rawInfo = (await response.json()) as RawInfoResponse;
-    const info = parseInfo(rawInfo);
-    this.info = info;
-    return info;
+    const text = await response.text();
+
+    try {
+      const rawInfo = JSON.parse(text) as RawInfoResponse;
+      const info = parseInfo(rawInfo);
+      this.info = info;
+      return info;
+    } catch (e) {
+      throw new Error(
+        `Error parsing the response of ${
+          this.transferServer
+        }/info as JSON: ${text}`,
+      );
+    }
   }
 
   protected getHeaders(): Headers {
@@ -282,9 +293,13 @@ export abstract class TransferProvider {
       }
     }
 
-    const { transaction }: { transaction: Transaction } = await response.json();
-
-    return _normalizeTransaction(transaction);
+    const text = await response.text();
+    try {
+      const { transaction }: { transaction: Transaction } = JSON.parse(text);
+      return _normalizeTransaction(transaction);
+    } catch (e) {
+      throw new Error(`Auth challenge response wasn't valid JSON: ${text}`);
+    }
   }
 
   /**
@@ -631,8 +646,14 @@ export abstract class TransferProvider {
           }
         }
 
-        const { fee: feeResponse } = await response.json();
-        return feeResponse as number;
+        const text = await response.text();
+
+        try {
+          const { fee: feeResponse } = JSON.parse(text);
+          return feeResponse as number;
+        } catch (e) {
+          throw new Error(`Fee endpoint returned invalid JSON: ${text}`);
+        }
 
       default:
         throw new Error(