Example: Theme switching migration

[chrispader]

This PR needs #27324 (review) to be merged first

@grgia

Details

Goal of this PR/Template

This PR aims to provide outlines and both a class component and functional component example of how to use the new theme switching logic in the Expensify app.

Migration process

In order to update a component so it uses the new theme switching, we have to do a few things:

1. Use the theme and styles with the newly introduced hooks and HOCs.
2. Replace all occurrences of styles imported from src/styles/styles.js with the styles from the ThemeStylesProvider
3. Replace all occurrences of theme colors imported from src/styles/theme/default.js with the theme from the ThemeProvider
4. Remove all imports of both of these static files

Implementation

Replacing imports

At the beginning of the file, you should have some imports like this:

import styles from '../../styles/styles';
import defaultTheme from '../../styles/themes/default';

These imports could be named slightly different like theme instead of defaultTheme, remove them anyway.

Remove these imports and replace it with the imports of the new hooks/HOCs. You might not need both hooks/HOCs, import only the ones you need:

Functional components

For functional components we introduced two hooks useTheme and useThemeStyles, both of which will give you the theme-adapted colors and styles. Add one or both of these lines:

import useTheme from '../../styles/themes/useTheme';
import useThemeStyles from '../../styles/useThemeStyles';

Class components

For class components we have to do things slightly different. We've introduced two HOCs withTheme and withThemeStyles, which will add the theme-adapted colors and styles to the props of your component. Add one or both of these lines:

import withTheme, {withThemePropTypes} from '../withTheme'; // Also import the propTypes !!
import withThemeStyles, {withThemeStylesPropTypes} from '../withThemeStyles'; // Also import the propTypes !!

Integrating the dynamic theme and styles

In order to migrate a component so that it uses the dynamic theme and styles provided by the theme switching logic, we'll have to do a few things:

Functional components

Use these two hooks at the beginning of the component:

function FunctionalComponent(props) {
    const theme = useTheme();
    const themeStyles = useThemeStyles();

    ...
}

Class components

Wrap the component with one or both of these HOCs. If the component already uses compose to wrap multiple HOCs, make sure to continue using it:

export default compose(
    ... // other HOCs
    withTheme,
    withThemeStyles,
)(
    React.forwardRef((props, ref) => (
        <ClassComponent
            // eslint-disable-next-line react/jsx-props-no-spreading
            {...props}
            forwardedRef={ref}
        />
    )),
);

By adding these HOCs, you should receive two objects theme and themeStyles inside the component's props. Make sure to add some convenience variables to the top of your render function and everywhere the theme and styles are used, so the code doesn't get too cluttered:

render() {
    const styles = this.props.themeStyles;
    const theme = this.props.theme;
    ...
    return (
        <SomeOtherComponent style={styles.someOtherComponent} />
    )
}

Replace all occurrences of static theme and styles

If the previous static imports were named exactly as the new dynamic theme and styles variables, we don't have to change anything.

If not, simply replace all occurrences of...

• staticStyles.someStyle. with styles.someStyle.
• and defaultTheme.someColor. with theme.someColor.

This can easily and quickly be done with the "Find and replace" function in the Editor/IDE of your choice. Still make sure, that only the right occurrences of this search pattern get replaced with the new code. (Don't mess up other stuff!🤠)

Wrapping it up

That's it! 🚀 Make sure to not change anything else or mess anything up by using "Find and replace" in your Editor/IDE. Also make sure to always use the provided TS types.

Fixed Issues

$ #27342

Tests

• Verify that no errors appear in the JS console

Offline tests

QA Steps

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android / native
  • Android / Chrome
  • iOS / native
  • iOS / Safari
  • MacOS / Chrome / Safari
  • MacOS / Desktop
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick)
  • I verified that the left part of a conditional rendering a React component is a boolean and NOT a string, e.g. myBool && <MyComponent />.
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
    • If any non-english text was added/modified, I verified the translation was requested/reviewed in #expensify-open-source and it was approved by an internal Expensify engineer. Link to Slack message:
  • I verified all numbers, amounts, dates and phone numbers shown in the product are using the localization methods
  • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is approved by marketing by adding the Waiting for Copy label for a copy review on the original GH to get the correct copy.
  • I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
  • I verified the JSDocs style guidelines (in STYLE.md) were followed
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
• I verified any variables that can be defined as constants (ie. in CONST.js or at the top of the file that uses the constant) are defined as such
• I verified that if a function's arguments changed that all usages have also been updated correctly
• If a new component is created I verified that:
  • A similar component doesn't exist in the codebase
  • All props are defined accurately and each prop has a /** comment above it */
  • The file is named correctly
  • The component has a clear name that is non-ambiguous and the purpose of the component can be inferred from the name alone
  • The only data being stored in the state is data necessary for rendering and nothing else
  • If we are not using the full Onyx data that we loaded, I've added the proper selector in order to ensure the component only re-renders when the data it is using changes
  • For Class Components, any internal methods passed to components event handlers are bound to this properly so there are no scoping issues (i.e. for onClick={this.submit} the method this.submit should be bound to this in the constructor)
  • Any internal methods bound to this are necessary to be bound (i.e. avoid this.submit = this.submit.bind(this); if this.submit is never passed to a component event handler like onClick)
  • All JSX used for rendering exists in the render method
  • The component has the minimum amount of code necessary for its purpose, and it is broken down into smaller components in order to separate concerns and functions
• If any new file was added I verified that:
  • The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(themeColors.componentBG))
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
• I have checked off every checkbox in the PR author checklist, including those that don't apply to this PR.

Screenshots/Videos

Web

Mobile Web - Chrome

Mobile Web - Safari

Desktop

iOS

Android

[grgia]

Some thoughts on readability

[grgia]

merged #27324

[chrispader]

@grgia Should i (ever) remove the "draft" from this PR? Or will this example stay draft forever? haha

In this case, i won't need to fill out PR author checklist and do the rest of the obligatory work...

[chrispader]

@grgia further simplified the guidelines/migration process in the PR description 👍

[grgia]

we decided to leave this as a draft for now

[chrispader]

Closing this since we're done migrating the app! 🚀