Solving the Mysterious TypeError: at ShadowCss.shimCssText (compiler.mjs) When Using CSS-Loader, Style-Loader with ngtools

Are you tired of encountering the cryptic TypeError: at ShadowCss.shimCssText (compiler.mjs) error when trying to use CSS-Loader and Style-Loader with ngtools? Well, you’re not alone! This error can be frustrating, but fear not, dear developer, for we’re about to embark on a journey to conquer this pesky issue once and for all.

Understanding the Problem

To understand why this error occurs, let’s take a step back and look at what’s happening under the hood. When using ngtools with CSS-Loader and Style-Loader, Angular’s compiler is trying to process CSS files using the ShadowCss plugin. This plugin is responsible for shimming CSS files, which means it wraps the CSS code in a way that allows Angular to properly parse and inject it into the component’s styles.

However, when something goes wrong, Angular’s compiler throws a TypeError: at ShadowCss.shimCssText (compiler.mjs) error, leaving you scratching your head. This error can occur due to various reasons, such as:

• Invalid CSS syntax
• Incorrect loader configurations
• Version conflicts between ngtools, CSS-Loader, and Style-Loader
• Incorrectly configured Angular modules

Diagnosing the Issue

Before we dive into the solutions, let’s take a closer look at the error message. The TypeError: at ShadowCss.shimCssText (compiler.mjs) error typically occurs during the build process, and the exact error message might look something like this:

ERROR in : TypeError: at ShadowCss.shimCssText (compiler.mjs:1346:15)
    at SyncDelegate._doSync (compiler.mjs:1334:15)
    at SyncDelegate.importSync (compiler.mjs:1309:27)
    at Object.importStyle (compiler.mjs:1291:23)
    at Object.loadStyles (compiler.mjs:1271:23)
    at compiler.mjs:1557:29
    at Array.forEach ()
    at Array.forEach ()
    at compiler.mjs:1555:15
    at compiler.mjs:1549:17

As you can see, the error is pointing to a specific line and column in the compiler.mjs file. This information can be helpful when debugging the issue.

Solution 1: Verify CSS Syntax

The first step in resolving this error is to ensure that your CSS files are syntactically correct. A single mistake in your CSS code can cause the entire build process to fail. To verify your CSS syntax, you can use a CSS linter or a code editor with built-in CSS syntax checking.

Here are some common CSS syntax mistakes to look out for:

• Missing semicolons at the end of rules
• Unclosed brackets or parentheses
• Mismatched property values (e.g., using a colon instead of an equals sign)
• Invalid property names or values

Solution 2: Configure Loaders Correctly

Another common reason for the TypeError: at ShadowCss.shimCssText (compiler.mjs) error is incorrect loader configurations. Make sure you have the correct versions of CSS-Loader and Style-Loader installed, and that your webpack.config.js file is configured correctly.

Here’s an example of a correctly configured webpack.config.js file:

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          'style-loader',
          {
            loader: 'css-loader',
            options: {
              importLoaders: true,
            },
          },
        ],
      },
    ],
  },
};

Solution 3: Resolve Version Conflicts

Version conflicts between ngtools, CSS-Loader, and Style-Loader can also cause the TypeError: at ShadowCss.shimCssText (compiler.mjs) error. Make sure you’re using compatible versions of these packages.

Here’s an example of how to check the versions of these packages using npm:

npm ls ngtools css-loader style-loader

Compare the versions of these packages with the compatible versions listed in the official documentation. If you find any version conflicts, update the packages to the compatible versions.

Solution 4: Configure Angular Modules Correctly

Incorrectly configured Angular modules can also cause the TypeError: at ShadowCss.shimCssText (compiler.mjs) error. Make sure you’ve imported the necessary modules and configured them correctly in your Angular application.

Here’s an example of how to configure the StyleModule in an Angular module:

import { NgModule } from '@angular/core';
import { StyleModule } from '@angular/animations';

@NgModule({
  imports: [StyleModule],
})
export class AppModule {}

Conclusion

The TypeError: at ShadowCss.shimCssText (compiler.mjs) error can be a frustrating and mysterious issue when using CSS-Loader and Style-Loader with ngtools. However, by following the steps outlined in this article, you should be able to diagnose and resolve the issue. Remember to verify your CSS syntax, configure your loaders correctly, resolve version conflicts, and configure your Angular modules correctly. With patience and persistence, you’ll be able to conquer this error and get your Angular application up and running smoothly.

Solution	Description
Verify CSS Syntax	Make sure your CSS files are syntactically correct
Configure Loaders Correctly	Ensure your webpack.config.js file is configured correctly
Resolve Version Conflicts	Make sure ngtools, CSS-Loader, and Style-Loader are compatible
Configure Angular Modules Correctly	Import and configure the necessary Angular modules correctly

By following these solutions, you’ll be well on your way to resolving the TypeError: at ShadowCss.shimCssText (compiler.mjs) error and getting your Angular application up and running smoothly. Happy coding!

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