CodeMirror as an ember-modifier

app-modifiers-code-mirror.ts

import { action } from "@ember/object";
import { bind } from "@ember/runloop";
import codemirror from "codemirror";
import Modifier from "ember-modifier";

import "codemirror/addon/edit/matchbrackets";
import "codemirror/addon/selection/active-line";
import "codemirror/mode/clike/clike";
import "codemirror/mode/go/go";
import "codemirror/mode/javascript/javascript";
import "codemirror/mode/python/python";

const EXTENSION_REGEXP = /(?:\.([^.]+))?$/;

/**
 * Maps file extensions to loaded, CodeMirror-compatible language modes.
 *
 * **Important:** These CodeMirror modes must be loaded to be useable. See
 * the above imports which load the supported language modes.
 */
const modeMap: Record<string, string> = {
  go: "text/x-go",
  java: "text/x-java",
  js: "javascript",
  py: "python",
};

/**
 * This is a magic CodeMirror mode string to indicate that no highlighting
 * should be used.
 *
 * See https://codemirror.net/doc/manual.html#option_mode.
 */
const DoNotHighlight = "null";

interface Args {
  named: {
    content: string;
    path: string;
    readOnly: boolean;
    onUpdate: (content: string) => void;
    [key: string]: unknown;
  };
  positional: never;
}

export default class CodeMirrorModifier extends Modifier<Args> {
  didInstall() {
    this._setup();
  }

  didUpdateArguments() {
    if (this._editor.getValue() !== this.args.named.content) {
      this._editor.setValue(this.args.named.content);
    }

    this._editor.setOption("readOnly", this.args.named.readOnly);
    this._editor.setOption("mode", this.mode);
  }

  private _editor!: CodeMirror.Editor;

  /**
   * Transforms the given path into an equivalent CodeMirror compatible
   * language mode string by inspecting the extension.
   *
   * If no matching language modes are supported or the file extension cannot be
   * determined, this will return the magic CodeMirror "null" string mode value.
   * The value "null" indicates no highlighting should be applied.
   */
  get mode() {
    if (!this.args.named.path) {
      return DoNotHighlight;
    }

    const extension = EXTENSION_REGEXP.exec(this.args.named.path);

    if (!extension || !extension[1]) {
      return DoNotHighlight;
    }

    return modeMap[extension[1].toLowerCase()] || DoNotHighlight;
  }

  @action
  private _onChange(editor: CodeMirror.Editor, _changeObject: CodeMirror.EditorChangeLinkedList) {
    this.args.named.onUpdate(editor.getValue());
  }

  private _setup() {
    if (!this.element) {
      throw new Error("CodeMirror modifier has no element");
    }

    const editor: CodeMirror.Editor = codemirror(this.element as HTMLElement, {
      lineNumbers: true,
      matchBrackets: true,
      mode: this.mode,
      readOnly: this.args.named.readOnly,
      styleActiveLine: true,
      theme: "my-custom-theme",
      value: this.args.named.content || "",
      viewportMargin: Infinity,
    });

    editor.on("change", bind(this, this._onChange));

    this._editor = editor;
  }
}

app-templates-caller-example.hbs

<div {{code-mirror content=@file.content onUpdate=this.update path=@file.path readOnly=@file.isSaving}}></div>

ember-cli-build.js

module.exports = function (defaults) {
  const app = new EmberApp(defaults, {
    app.import("node_modules/codemirror/lib/codemirror.css");
  })
})

package.json

{
  "devDependencies": {
    "@types/codemirror": "^0.0.106",
    "codemirror": "^5.59.2",
    "ember-modifier": "^2.1.1",
  }
}