google is not defined

Reproduction

Setup

1. Install D8
2. Install Google Map Field
3. Install Paragraphs
4. Create a Paragraph with a Google Map Field
5. Create a Content Type containing that Paragraph as field
6. Create content using the content type
7. On the content form, try adding the paragraph

Expected

• A paragraph containing Google Map Field appears
• An initial map preview appears

Actual

• No initial map preview appears on the widget (symptom)
• "google is not defined" error appears in the console

What's happening

On Step 7, when Drupal tries to load a paragraph instance, Drupal sends down a bunch of commands to the browser (see attachment). By index item #2 (insert), Drupal appends a bunch of script tags to the page, in dependency order. By item #4 (insert), module behaviors are executed. The problem is that the Google Maps API script executes after the behaviors execute, causing references to "google" to blow up.

It might be because the scripts are appended dynamically, thus load asynchronously and execute out of order. This is not an issue when the field is loaded on page load (i.e. not using Paragraphs) since scripts are printed on HTML and will run in the correct order on page load.

Potential solution

Execute module scripts only after Google Maps API has executed by adding a callback. This ensures that it works for both synchronous and asychronously-loaded Google Maps API. See the Simple Map example.