(core) Improving error messages on file imports

Summary: Improving error messages that get returned from "Import from URL" plugin.

Test Plan: browser tests

Reviewers: alexmojaki

Reviewed By: alexmojaki

Subscribers: dsagal, alexmojaki

Differential Revision: https://phab.getgrist.com/D2946

app/server/lib/DocPluginManager.ts

@@ -101,6 +101,10 @@ export class DocPluginManager {
       }
     }
 
+    if (path.extname(fileName) === '.grist') {
+      throw new Error(`To import a grist document use the "Import document" menu option on your home screen`);
+    }
+
     const matchingFileParsers: FileParserElement[] = FileParserElement.getMatching(this._pluginInstances, fileName);
 
     if (!this._tmpDir) {
@@ -128,8 +132,18 @@ export class DocPluginManager {
         continue;
       }
     }
-    const details = messages.length ? ": " + messages.join("; ") : "";
-    throw new Error(`Cannot parse this data${details}`);
+
+    if (messages.length) {
+      const extToType: Record<string, string> = {
+        '.xlsx' : 'Excel',
+        '.xls' : 'Excel',
+        '.json' : 'JSON',
+        '.csv' : 'CSV',
+      };
+      const fileType = extToType[path.extname(fileName)] || path.extname(fileName);
+      throw new Error(`Failed to parse ${fileType} file. Error: ${messages.join("; ")}`);
+    }
+    throw new Error(`File format is not supported.`);
   }
 
   /**

app/server/lib/uploads.ts

@@ -337,6 +337,7 @@ export async function fetchURL(url: string, accessId: string|null): Promise<Uplo
  */
 async function _fetchURL(url: string, accessId: string|null, fileName: string,
                          headers?: {[key: string]: string}): Promise<UploadResult> {
+  try {
     const response: FetchResponse = await Deps.fetch(url, {
       redirect: 'follow',
       follow: 10,
@@ -367,6 +368,14 @@ async function _fetchURL(url: string, accessId: string|null, fileName: string,
     log.debug(`done fetching url: ${url} to ${destPath}`);
     const uploadId = globalUploadSet.registerUpload([uploadedFile], tmpDir, cleanupCallback, accessId);
     return {uploadId, files: [pick(uploadedFile, ['origName', 'size', 'ext'])]};
+  } catch(err) {
+    if (err?.code === "EPROTO" || // https vs http error
+        err?.code === "ECONNREFUSED" || // server does not listen
+        err?.code === "ENOTFOUND") { // could not resolve domain
+      throw new ApiError(`Can't connect to the server. The URL seems to be invalid. Error code ${err.code}`, 400);
+    }
+    throw err;
+  }
 }
 
 /**
@@ -392,10 +401,32 @@ async function fetchDoc(homeUrl: string, docId: string, req: Request, accessId:
 
 // Re-issue failures as exceptions.
 async function _checkForError(response: FetchResponse) {
-  if (response.ok) { return; }
+  if (response.status === 403) {
+    throw new ApiError("Access to this resource was denied.", response.status);
+  }
+  if (response.ok) {
+    const contentType = response.headers.get("content-type");
+    if (contentType?.startsWith("text/html")) {
+      // Probably we hit some login page
+      if (response.url.startsWith("https://accounts.google.com")) {
+        throw new ApiError("Importing directly from a Google Drive URL is not supported yet. " +
+        'Use the "Import from Google Drive" menu option instead.', 403);
+      } else {
+        throw new ApiError("Could not import the requested file, check if you have all required permissions.", 403);
+      }
+    }
+    return;
+   }
   const body = await response.json().catch(() => ({}));
+  if (response.status === 404) {
+    throw new ApiError("File can't be found at the requested URL.", 404);
+  } else if (response.status >= 500 && response.status < 600) {
+    throw new ApiError(`Remote server returned an error (${body.error || response.statusText})`,
+      response.status, body.details);
+  } else {
     throw new ApiError(body.error || response.statusText, response.status, body.details);
   }
+}
 
 /**
  * Create an access identifier, combining the userId supplied with the host of the