34 lines
2.5 KiB
Markdown
34 lines
2.5 KiB
Markdown
# Update `module` and `target` compiler options migration
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## What does this migration do?
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This migration adjusts the [`target`](https://www.typescriptlang.org/v2/en/tsconfig#target) and [`module`](https://www.typescriptlang.org/v2/en/tsconfig#module) settings within the [TypeScript configuration files](guide/typescript-configuration) for the workspace.
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The changes to each option vary based on the builder or command that uses the TypeScript configuration file.
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Unless otherwise noted, changes are only made if the existing value was not changed since the project was created.
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This process helps ensure that intentional changes to the options are kept in place.
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TypeScript Configuration File(s) | Changed Property | Existing Value | New Value
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------------- | ------------- | ------------- | ------------- | -------------
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`<workspace base>/tsconfig.base.json` | `"module"` | `"esnext"` | `"es2020"`
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Used in `browser` builder options (`ng build` for applications) | `"module"` | `"esnext"` | `"es2020"`
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Used in `ng-packgr` builder options (`ng build` for libraries) | `"module"` | `"esnext"` | `"es2020"`
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Used in `karma` builder options (`ng test` for applications) | `"module"` | `"esnext"` | `"es2020"`
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Used in `server` builder options (universal) | `"module"` | `"commonjs"` | _removed_
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Used in `server` builder options (universal) | `"target"` | _any_ | `"es2016"`
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Used in `protractor` builder options (`ng e2e` for applications) | `"target"` | `"es5"` | `"es2018"`
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## Why is this migration necessary?
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This migration provides improvements to the long-term supportability of projects by updating the projects to use recommended best practice compilation options.
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For the functionality that executes on Node.js, such as Universal and Protractor, the new settings provide performance and troubleshooting benefits as well.
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The minimum Node.js version for the Angular CLI (v10.13) supports features in ES2018 and earlier.
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By targeting later ES versions, the compiler transforms less code and can use newer features directly.
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Since zone.js does not support native `async` and `await`, the universal builds still target ES2016.
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## Why `"es2020"` instead of `"esnext"`?
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In TypeScript 3.9, the behavior of the TypeScript compiler controlled by `module` is the same with both `"esnext"` and `"es2020"` values.
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This behavior can change in the future, because the `"esnext"` option could evolve in a backwards incompatible ways, resulting in build-time or run-time errors during a TypeScript update.
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As a result, code can become unstable. Using the `"es2020"` option mitigates this risk.
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