[Tools] Add string concatenation parsing (#25381)

src/dev/i18n/__snapshots__/utils.test.js.snap

@@ -16,6 +16,8 @@ exports[`i18n utils should not escape linebreaks 1`] = `
 "
 `;
 
+exports[`i18n utils should parse string concatenation 1`] = `"Very long concatenated string"`;
+
 exports[`i18n utils should throw if "values" has a value that is unused in the message 1`] = `
 "\\"values\\" object contains unused properties (\\"namespace.message.id\\"):
 [url]."

src/dev/i18n/utils.js

@@ -26,6 +26,7 @@ import {
   isObjectProperty,
   isStringLiteral,
   isTemplateLiteral,
+  isBinaryExpression,
 } from '@babel/types';
 import fs from 'fs';
 import glob from 'glob';
@@ -212,7 +213,7 @@ function parseTemplateLiteral(node, messageId) {
   return node.quasis[0].value.cooked;
 }
 
-export function extractMessageValueFromNode(node, messageId) {
+function extractStringFromNode(node, messageId, errorMessage) {
   if (isStringLiteral(node)) {
     return node.value;
   }
@@ -221,21 +222,28 @@ export function extractMessageValueFromNode(node, messageId) {
     return parseTemplateLiteral(node, messageId);
   }
 
-  throw createFailError(
+  if (isBinaryExpression(node, { operator: '+' })) {
+    return (
+      extractStringFromNode(node.left, messageId, errorMessage) +
+      extractStringFromNode(node.right, messageId, errorMessage)
+    );
+  }
+
+  throw createFailError(errorMessage);
+}
+
+export function extractMessageValueFromNode(node, messageId) {
+  return extractStringFromNode(
+    node,
+    messageId,
     `defaultMessage value should be a string or template literal ("${messageId}").`
   );
 }
 
 export function extractDescriptionValueFromNode(node, messageId) {
-  if (isStringLiteral(node)) {
-    return node.value;
-  }
-
-  if (isTemplateLiteral(node)) {
-    return parseTemplateLiteral(node, messageId);
-  }
-
-  throw createFailError(
+  return extractStringFromNode(
+    node,
+    messageId,
     `description value should be a string or template literal ("${messageId}").`
   );
 }

src/dev/i18n/utils.test.js

@@ -18,7 +18,7 @@
  */
 
 import { parse } from '@babel/parser';
-import { isExpressionStatement, isObjectExpression } from '@babel/types';
+import { isExpressionStatement, isObjectExpression, isObjectProperty } from '@babel/types';
 
 import {
   isI18nTranslateFunction,
@@ -27,6 +27,7 @@ import {
   formatJSString,
   checkValuesProperty,
   createParserErrorMessage,
+  extractMessageValueFromNode,
 } from './utils';
 
 const i18nTranslateSources = ['i18n', 'i18n.translate'].map(
@@ -153,4 +154,16 @@ describe('i18n utils', () => {
       checkValuesProperty(valuesKeys, defaultMessage, messageId)
     ).toThrowErrorMatchingSnapshot();
   });
+
+  test(`should parse string concatenation`, () => {
+    const source = `
+i18n('namespace.id', {
+  defaultMessage: 'Very ' + 'long ' + 'concatenated ' + 'string',
+});`;
+    const objectProperty = [...traverseNodes(parse(source).program.body)].find(node =>
+      isObjectProperty(node)
+    );
+
+    expect(extractMessageValueFromNode(objectProperty.value)).toMatchSnapshot();
+  });
 });