Merge pull request #601 from jrafanie/clarify-string-extraction-methods-require-string-literals

Further clarify __() and friends expect string literals

Author: Fryguy

i18n.md

@@ -121,16 +121,20 @@ will result in the whole
 
 block being collected during string extraction by `yarn run gettext:extract`. Correctly, the `translate` directive should be placed inside the `span` element.
 
-* **Don't use dynamic content inside `__()`**. For example, the following javascript code won't be collected correctly by `yarn run gettext:extract`.
+* **Don't use dynamic content inside `__()`**. The argument to `__()` should be a string literal. GNU gettext and libraries built on top of it, such as the Ruby and JavaScript gettext extractors, perform string extraction statically, so expressions, concatenation, interpolation, and other dynamically built values will not be collected correctly by `yarn run gettext:extract`.
+
+For example, the following javascript code won't be collected correctly:
 
 ```javascript
 s = __(sprintf("My name is %s.", me.name));
+message = __('xyz' + 'abc');
 ```
 
-The above should correctly be:
+These examples should correctly be:
 
 ```javascript
 s = sprintf(__("My name is %s."), me.name);
+message = __("xyzabc");
 ```
 
 * **Don't apply the `translate` filter on a dynamic content**. The string inside would not be correctly extracted during string collection. For example the following won't be collected correctly by `yarn run gettext:extract`.