Handle fetch error

src/append.js

@@ -1,4 +1,5 @@
-const isRequired = require("./argIsRequired"),
+const isRequired = require("./lib/argIsRequired"),
+  processFetchResponse = require("./lib/processFetchResponse"),
   base64Encode = require("universal-base64").encode,
   fetch = require("isomorphic-unfetch");
 
@@ -24,7 +25,10 @@ module.exports = (url, sheetName, rows, { authentication }) => {
   return new Promise((resolve, reject) => {
     fetch(url, options)
       .then(apiResponse => {
-        resolve(apiResponse.json());
+        return processFetchResponse(apiResponse);
+      })
+      .then(data => {
+        resolve(data);
       })
       .catch(err => {
         reject(err);

src/delete.js

@@ -1,4 +1,5 @@
-const isRequired = require("./argIsRequired"),
+const isRequired = require("./lib/argIsRequired"),
+  processFetchResponse = require("./lib/processFetchResponse"),
   base64Encode = require("universal-base64").encode,
   fetch = require("isomorphic-unfetch");
 
@@ -31,7 +32,10 @@ module.exports = (url, sheetName, { search, limit, authentication }) => {
   return new Promise((resolve, reject) => {
     fetch(url, options)
       .then(apiResponse => {
-        resolve(apiResponse.json());
+        return processFetchResponse(apiResponse);
+      })
+      .then(data => {
+        resolve(data);
       })
       .catch(err => {
         reject(err);

src/edit.js

@@ -1,4 +1,5 @@
-const isRequired = require("./argIsRequired"),
+const isRequired = require("./lib/argIsRequired"),
+  processFetchResponse = require("./lib/processFetchResponse"),
   base64Encode = require("universal-base64").encode,
   fetch = require("isomorphic-unfetch");
 
@@ -32,7 +33,10 @@ module.exports = (url, sheetName, { search, set, limit, authentication }) => {
   return new Promise((resolve, reject) => {
     fetch(url, options)
       .then(apiResponse => {
-        resolve(apiResponse.json());
+        return processFetchResponse(apiResponse);
+      })
+      .then(data => {
+        resolve(data);
       })
       .catch(err => {
         reject(err);

src/lib/processFetchResponse.js

@@ -0,0 +1,32 @@
+module.exports = (response) => {
+  if (response.ok) {
+    return response.json();
+  } else {
+    return handleResponseNotOk(response);
+  }
+};
+
+function handleResponseNotOk(response) {
+  return response.json()
+    .then(data => {
+      if (!data.error) {
+        // error not from Stein server, probably from web server, proxy server, etc.
+        return createHttpError(response);
+      } else {
+        return new Error(data.error);
+      }
+    })
+    .catch(() => {
+      // not a JSON document
+      return createHttpError(response);
+    })
+    .then((error) => {
+      throw error;
+    });
+}
+
+function createHttpError(response) {
+  const error = new Error(`HTTP ${response.status} ${response.statusText}`);
+  error.response = response; // include response object so users can access the error page
+  return error;
+}

src/read.js

@@ -1,4 +1,5 @@
-const isRequired = require("./argIsRequired"),
+const isRequired = require("./lib/argIsRequired"),
+  processFetchResponse = require("./lib/processFetchResponse"),
   base64Encode = require("universal-base64").encode,
   fetch = require("isomorphic-unfetch");
 
@@ -30,13 +31,10 @@ module.exports = (
     // Add all rows to the array
     fetch(url, options)
       .then(apiResponse => {
-        if (!apiResponse.ok) {
-          return apiResponse.json().then(error => {
-            throw new Error(error.error);
-          });
-        }
-
-        resolve(apiResponse.json());
+        return processFetchResponse(apiResponse);
+      })
+      .then(data => {
+        resolve(data);
       })
       .catch(response => {
         reject(response);