plain.importmap

Use import maps in templates.

Heavily inspired by rails/importmap-rails, this app adds a simple process for integrating import maps into Django.

This is a new project and it hasn't been used in production yet. But if you're looking to use import maps with Django, give it a try and tell us how it goes. The structure (and code) is pretty simple. Contributions are welcome!

How to use it

You'll need to do four things to use plain-importmap.

The TL;DR is:

• Add "importmap" to INSTALLED_PACKAGES
• Create an importmap.toml
• Run python manage.py importmap_generate
• Use {% importmap_js %} in your template

1. Install it

Do the equivalent of pip install plain-importmap and add it to your INSTALLED_PACKAGES list in your settings.py file.

# settings.py
INSTALLED_PACKAGES = [
    ...
    "importmap",
]

2. Create an importmap.toml file

This should live next to your manage.py file. Here you'll add a list of "packages" you want to use.

The "name" can be anything, but should probably be the same as what it you would import from in typical bundling setups (i.e. import React from "react").

The "source" will get passed on to the jspm.org generator, but is basically the <npm package>@<version> you want to use.

[[packages]]
name = "react"
source = "react@17.0.2"

3. Run importmap_generate

To resolve the import map, you'll need to run python manage.py importmap_generate.

This will create importmap.lock (which you should save and commit to your repo) that contains the actual import map JSON (both for development and production).

You don't need to look at this file yourself, but here is an example of what it will contain:

{
  "config_hash": "09d6237cdd891aad07de60f54689d130",
  "importmap": {
    "imports": {
      "react": "https://ga.jspm.io/npm:react@17.0.2/index.js"
    },
    "scopes": {
      "https://ga.jspm.io/": {
        "object-assign": "https://ga.jspm.io/npm:object-assign@4.1.1/index.js"
      }
    }
  },
  "importmap_dev": {
    "imports": {
      "react": "https://ga.jspm.io/npm:react@17.0.2/dev.index.js"
    },
    "scopes": {
      "https://ga.jspm.io/": {
        "object-assign": "https://ga.jspm.io/npm:object-assign@4.1.1/index.js"
      }
    }
  }
}

4. Add the scripts to your template

The import map itself gets added by using {% load importmap %} and then {% importmap_js %} in the head of your HTML. This will include the es-module-shim.

After that, you can include your own JavaScript! This could be inline or from static. Just be sure to use type="module" and the "name" you provided when doing your JS imports (i.e. "react").

{% load importmap %}
<!DOCTYPE html>
<html lang="en">
<head>
    {% importmap_js %}
    <script type="module">
        import React from "react"

        console.log(React);
    </script>
</head>
<body>

</body>
</html>

When it renders you should get something like this:

<!DOCTYPE html>
<html lang="en">
<head>
    <script async src="https://ga.jspm.io/npm:es-module-shims@1.3.6/dist/es-module-shims.js"></script>
    <script type="importmap">
    {
        "imports": {
            "react": "https://ga.jspm.io/npm:react@17.0.2/dev.index.js"
        },
        "scopes": {
            "https://ga.jspm.io/": {
                "object-assign": "https://ga.jspm.io/npm:object-assign@4.1.1/index.js"
            }
        }
    }
    </script>

    <script type="module">
        import React from "react"

        console.log(React);
    </script>
</head>
<body>

</body>
</html>

Project status

This is partly an experiment, but honestly it's so simple that I don't think there can be much wrong with how it works currently.

Here's a list of things that would be nice to do (PRs welcome):

• Command to add new importmap dependency (use ^ version automatically?)
• Django check for comparing lock and config (at deploy time, etc.)
• Use deps to update shim version
• Preload option
• Vendoring option (including shim)
• More complete error handling (custom exceptions, etc.)