Add `Message.createImporter`

js/modules/types/message.js

@@ -1,4 +1,4 @@
-const { isFunction } = require('lodash');
+const { isFunction, isString, omit } = require('lodash');
 
 const Attachment = require('./attachment');
 const Errors = require('./errors');
@@ -176,3 +176,50 @@ exports.upgradeSchema = async (message, { writeNewAttachmentData } = {}) => {
     { writeNewAttachmentData }
   );
 };
+
+//      createImporter :: (RelativePath -> IO Unit)
+//                        Message ->
+//                        IO (Promise Message)
+exports.createImporter = (writeExistingAttachmentData) => {
+  if (!isFunction(writeExistingAttachmentData)) {
+    throw new TypeError('"writeExistingAttachmentData" must be a function');
+  }
+
+  return async (message) => {
+    if (!exports.isValid(message)) {
+      throw new TypeError('"message" is not valid');
+    }
+
+    const { attachments } = message;
+    const hasAttachments = attachments && attachments.length > 0;
+    if (!hasAttachments) {
+      return message;
+    }
+
+    const lastVersionWithAttachmentDataInMemory = 2;
+    const willHaveAttachmentsSavedOnFileSystemDuringUpgrade =
+      message.schemaVersion <= lastVersionWithAttachmentDataInMemory;
+    if (willHaveAttachmentsSavedOnFileSystemDuringUpgrade) {
+      return message;
+    }
+
+    attachments.forEach((attachment) => {
+      if (!Attachment.hasData(attachment)) {
+        throw new TypeError('"attachment.data" is required during message import');
+      }
+
+      if (!isString(attachment.path)) {
+        throw new TypeError('"attachment.path" is required');
+      }
+    });
+
+    const messageWithoutAttachmentData = Object.assign({}, message, {
+      attachments: await Promise.all(attachments.map(async (attachment) => {
+        await writeExistingAttachmentData(attachment);
+        return omit(attachment, ['data']);
+      })),
+    });
+
+    return messageWithoutAttachmentData;
+  };
+};

preload.js

@@ -114,6 +114,7 @@ const attachmentsPath = Attachments.getPath(app.getPath('userData'));
 const deleteAttachmentData = Attachments.createDeleter(attachmentsPath);
 const readAttachmentData = Attachments.createReader(attachmentsPath);
 const writeNewAttachmentData = Attachments.createWriterForNew(attachmentsPath);
+const writeExistingAttachmentData = Attachments.createWriterForExisting(attachmentsPath);
 
 // Injected context functions to keep `Message` agnostic from Electron:
 const upgradeSchemaContext = {
@@ -137,6 +138,8 @@ window.Signal.Migrations = {};
 window.Signal.Migrations.deleteAttachmentData =
   Attachment.deleteData(deleteAttachmentData);
 window.Signal.Migrations.getPlaceholderMigrations = getPlaceholderMigrations;
+window.Signal.Migrations.importMessage =
+  Message.createImporter(writeExistingAttachmentData);
 window.Signal.Migrations.loadAttachmentData = Attachment.loadData(readAttachmentData);
 window.Signal.Migrations.Migrations0DatabaseWithAttachmentData =
   require('./js/modules/migrations/migrations_0_database_with_attachment_data');

test/modules/types/message_test.js

@@ -5,6 +5,66 @@ const { stringToArrayBuffer } = require('../../../js/modules/string_to_array_buf
 
 
 describe('Message', () => {
+  describe('createImporter', () => {
+    it('should ignore messages that didn’t go through attachment migration', async () => {
+      const input = {
+        body: 'Imagine there is no heaven…',
+        schemaVersion: 2,
+      };
+      const expected = {
+        body: 'Imagine there is no heaven…',
+        schemaVersion: 2,
+      };
+      const writeExistingAttachmentData = () => {};
+
+      const actual = await Message.createImporter(writeExistingAttachmentData)(input);
+      assert.deepEqual(actual, expected);
+    });
+
+    it('should ignore messages without attachments', async () => {
+      const input = {
+        body: 'Imagine there is no heaven…',
+        schemaVersion: 4,
+        attachments: [],
+      };
+      const expected = {
+        body: 'Imagine there is no heaven…',
+        schemaVersion: 4,
+        attachments: [],
+      };
+      const writeExistingAttachmentData = () => {};
+
+      const actual = await Message.createImporter(writeExistingAttachmentData)(input);
+      assert.deepEqual(actual, expected);
+    });
+
+    it('should write attachments to file system on original path', async () => {
+      const input = {
+        body: 'Imagine there is no heaven…',
+        schemaVersion: 4,
+        attachments: [{
+          path: 'ab/abcdefghi',
+          data: stringToArrayBuffer('It’s easy if you try'),
+        }],
+      };
+      const expected = {
+        body: 'Imagine there is no heaven…',
+        schemaVersion: 4,
+        attachments: [{
+          path: 'ab/abcdefghi',
+        }],
+      };
+
+      const writeExistingAttachmentData = (attachment) => {
+        assert.equal(attachment.path, 'ab/abcdefghi');
+        assert.deepEqual(attachment.data, stringToArrayBuffer('It’s easy if you try'));
+      };
+
+      const actual = await Message.createImporter(writeExistingAttachmentData)(input);
+      assert.deepEqual(actual, expected);
+    });
+  });
+
   describe('initializeSchemaVersion', () => {
     it('should ignore messages with previously inherited schema', () => {
       const input = {