54 lines
2.3 KiB
Markdown
54 lines
2.3 KiB
Markdown
This folder is used to hold any components/code that will get exported to the
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legacy build.
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> Currently, builds in this folder target WP < 5.3
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When you add a file, add it in the same folder structure as the root.
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So for example, if the original file was in:
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`assets/js/base/components/label/index.js`
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Then the legacy version will be located in:
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`assets/js/legacy/base/components/label/index.js`
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Note: you _must_ copy all files related to the entry point for that module according to the path aliased.
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Legacy builds will be identical to the main builds except:
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- files will have a `-legacy` suffix (so server can conditionally enqueue). It is expected that the server will load either the main or the legacy bundles, not both.
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- any imports not in the legacy folder will fallback to the main file.
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## How does the legacy system work?
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Short answer, through the magic of WebPack! Long answer:
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### A. Aliases
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We use aliases for paths covering anything that might need a legacy version. Then we have a dedicated builds for main and legacy code.
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Current aliases are:
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- `@woocommerce/base-components` -> `assets/js/base/components/`
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- `@woocommerce/base-hocs` -> `assets/js/base/hocs/`
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- `@woocommerce/block-components` -> `assets/js/components`
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- `@woocommerce/block-hocs` -> `assets/js/block-hocs`
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- `@woocommerce/atomic-components` -> `assets/js/atomic/components/`
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When importing, if outside the module referenced by that path, import from the alias. That will ensure that at compile time the bundles can pull from the appropriate location.
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Example:
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```js
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// will pull from '/assets/js/base/components/label/index.js in the main build
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// will pull from '/assets/js/legacy/base/components/label/index.js in the legacy
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// build.
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import { Label } from '@woocommerce/base-components/label';
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```
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### B. Webpack Plugin
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The second part of the webpack magic is a custom plugin. Located in `bin/fallback-module-directory-webpack-plugin.js`, this custom plugin is used instead of the default Alias plugin. It handles trying a fallback if the original path aliased to does not exist. The fallback is a variation of the aliased path using the provided `search` and `replace` strings when instantiating the plugin. You can see it setup in the `LegacyBlocksConfig.resolve.plugins` property of the `webpack.config.js` file.
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