Fixing incorrectly typed token decimal attribute

app/scripts/controllers/preferences.js

@@ -378,7 +378,7 @@ export default class PreferencesController {
    */
   async addToken(rawAddress, symbol, decimals, image) {
     const address = normalizeAddress(rawAddress);
-    const newEntry = { address, symbol, decimals };
+    const newEntry = { address, symbol, decimals: Number(decimals) };
     const { tokens, hiddenTokens } = this.store.getState();
     const assetImages = this.getAssetImages();
     const updatedHiddenTokens = hiddenTokens.filter(

app/scripts/migrations/054.js

@@ -0,0 +1,69 @@
+import { cloneDeep } from 'lodash';
+
+const version = 54;
+
+function isValidDecimals(decimals) {
+  return !isNaN(Number(decimals));
+}
+
+/**
+ * Migrates preference tokens with 0 decimals typed as 'string' to 'number'
+ */
+export default {
+  version,
+  async migrate(originalVersionedData) {
+    const versionedData = cloneDeep(originalVersionedData);
+    versionedData.meta.version = version;
+    const state = versionedData.data;
+    const newState = transformState(state);
+    versionedData.data = newState;
+    return versionedData;
+  },
+};
+
+function transformState(state) {
+  const newState = state;
+
+  if (!newState.PreferencesController) {
+    return newState;
+  }
+
+  const tokens = newState.PreferencesController.tokens || [];
+  // Filter out any tokens with corrupted decimal values
+  const validTokens = tokens.filter(({ decimals }) =>
+    isValidDecimals(decimals),
+  );
+  for (const token of validTokens) {
+    // In the case of a decimal value type string, set to 0.
+    if (typeof token.decimals === 'string') {
+      token.decimals = 0;
+    }
+  }
+  newState.PreferencesController.tokens = validTokens;
+
+  const { accountTokens } = newState.PreferencesController;
+  if (accountTokens && typeof accountTokens === 'object') {
+    for (const address of Object.keys(accountTokens)) {
+      const networkTokens = accountTokens[address];
+      if (networkTokens && typeof networkTokens === 'object') {
+        for (const network of Object.keys(networkTokens)) {
+          const tokensOnNetwork = networkTokens[network] || [];
+          // Filter out any tokens with corrupted decimal values
+          const validTokensOnNetwork = tokensOnNetwork.filter(({ decimals }) =>
+            isValidDecimals(decimals),
+          );
+          // In the case of a decimal value type string, set to 0.
+          for (const token of validTokensOnNetwork) {
+            if (typeof token.decimals === 'string') {
+              token.decimals = 0;
+            }
+          }
+          networkTokens[network] = validTokensOnNetwork;
+        }
+      }
+    }
+  }
+  newState.PreferencesController.accountTokens = accountTokens;
+
+  return newState;
+}