Use standard select element for small number of authors.

packages/editor/src/components/post-author/combobox.js

@@ -0,0 +1,108 @@
+/**
+ * External dependencies
+ */
+import { debounce } from 'lodash';
+
+/**
+ * WordPress dependencies
+ */
+import { useState, useMemo, useEffect } from '@wordpress/element';
+import { useSelect, useDispatch } from '@wordpress/data';
+import { __ } from '@wordpress/i18n';
+import { ComboboxControl } from '@wordpress/components';
+
+function PostAuthorCombobox() {
+	const [ fieldValue, setFieldValue ] = useState();
+
+	const { authorId, isLoading, authors, postAuthor } = useSelect(
+		( select ) => {
+			const { __unstableGetAuthor, getAuthors, isResolving } = select(
+				'core'
+			);
+			const { getEditedPostAttribute } = select( 'core/editor' );
+			const author = __unstableGetAuthor(
+				getEditedPostAttribute( 'author' )
+			);
+			const query =
+				! fieldValue || '' === fieldValue ? {} : { search: fieldValue };
+			return {
+				authorId: getEditedPostAttribute( 'author' ),
+				postAuthor: author,
+				authors: getAuthors( query ),
+				isLoading: isResolving( 'core', 'getAuthors', [ query ] ),
+			};
+		},
+		[ fieldValue ]
+	);
+	const { editPost } = useDispatch( 'core/editor' );
+
+	const authorOptions = useMemo( () => {
+		const fetchedAuthors = ( authors ?? [] ).map( ( author ) => {
+			return {
+				value: author.id,
+				label: author.name,
+			};
+		} );
+
+		// Ensure the current author is included in the dropdown list.
+		const foundAuthor = fetchedAuthors.findIndex(
+			( { value } ) => postAuthor?.id === value
+		);
+
+		if ( foundAuthor < 0 && postAuthor ) {
+			return [
+				{ value: postAuthor.id, label: postAuthor.name },
+				...fetchedAuthors,
+			];
+		}
+
+		return fetchedAuthors;
+	}, [ authors, postAuthor ] );
+
+	// Initializes the post author properly
+	// Also ensures external changes are reflected.
+	useEffect( () => {
+		if ( postAuthor ) {
+			setFieldValue( postAuthor.name );
+		}
+	}, [ postAuthor ] );
+
+	/**
+	 * Handle author selection.
+	 *
+	 * @param {number} postAuthorId The selected Author.
+	 */
+	const handleSelect = ( postAuthorId ) => {
+		if ( ! postAuthorId ) {
+			return;
+		}
+		editPost( { author: postAuthorId } );
+	};
+
+	/**
+	 * Handle user input.
+	 *
+	 * @param {string} inputValue The current value of the input field.
+	 */
+	const handleKeydown = ( inputValue ) => {
+		setFieldValue( inputValue );
+	};
+
+	if ( ! postAuthor ) {
+		return null;
+	}
+
+	return (
+		<ComboboxControl
+			label={ __( 'Author' ) }
+			options={ authorOptions }
+			value={ authorId }
+			onFilterValueChange={ debounce( handleKeydown, 300 ) }
+			onChange={ handleSelect }
+			isLoading={ isLoading }
+			allowReset={ false }
+		/>
+	);
+}
+
+export default PostAuthorCombobox;

packages/editor/src/components/post-author/index.js

@@ -1,115 +1,29 @@
-/**
- * External dependencies
- */
-import { debounce } from 'lodash';
-
 /**
  * WordPress dependencies
  */
-import { useState, useMemo, useEffect } from '@wordpress/element';
-import { useSelect, useDispatch } from '@wordpress/data';
-import { __ } from '@wordpress/i18n';
-import { ComboboxControl } from '@wordpress/components';
+import { useSelect } from '@wordpress/data';
 
 /**
  * Internal dependencies
  */
-import PostAuthorCheck from './check';
+import PostAuthorCombobox from './combobox';
+import PostAuthorSelect from './select';
 
-function PostAuthor() {
-	const [ fieldValue, setFieldValue ] = useState();
+const minimumUsersForCombobox = 25;
 
-	const { authorId, isLoading, authors, postAuthor } = useSelect(
-		( select ) => {
-			const { __unstableGetAuthor, getAuthors, isResolving } = select(
-				'core'
-			);
-			const { getEditedPostAttribute } = select( 'core/editor' );
-			const author = __unstableGetAuthor(
-				getEditedPostAttribute( 'author' )
-			);
-			const query =
-				! fieldValue || '' === fieldValue ? {} : { search: fieldValue };
-			return {
-				authorId: getEditedPostAttribute( 'author' ),
-				postAuthor: author,
-				authors: getAuthors( query ),
-				isLoading: isResolving( 'core', 'getAuthors', [ query ] ),
-			};
-		},
-		[ fieldValue ]
-	);
-	const { editPost } = useDispatch( 'core/editor' );
-
-	const authorOptions = useMemo( () => {
-		const fetchedAuthors = ( authors ?? [] ).map( ( author ) => {
-			return {
-				value: author.id,
-				label: author.name,
-			};
+function PostAuthor() {
+	const showCombobox = useSelect( ( select ) => {
+		const authors = select( 'core' ).getUsers( {
+			who: 'authors',
+			per_page: minimumUsersForCombobox + 1,
 		} );
+		return authors?.length >= minimumUsersForCombobox;
+	}, [] );
 
-		// Ensure the current author is included in the dropdown list.
-		const foundAuthor = fetchedAuthors.findIndex(
-			( { value } ) => postAuthor?.id === value
-		);
-
-		if ( foundAuthor < 0 && postAuthor ) {
-			return [
-				{ value: postAuthor.id, label: postAuthor.name },
-				...fetchedAuthors,
-			];
-		}
-
-		return fetchedAuthors;
-	}, [ authors, postAuthor ] );
-
-	// Initializes the post author properly
-	// Also ensures external changes are reflected.
-	useEffect( () => {
-		if ( postAuthor ) {
-			setFieldValue( postAuthor.name );
-		}
-	}, [ postAuthor ] );
-
-	/**
-	 * Handle author selection.
-	 *
-	 * @param {number} postAuthorId The selected Author.
-	 */
-	const handleSelect = ( postAuthorId ) => {
-		if ( ! postAuthorId ) {
-			return;
-		}
-		editPost( { author: postAuthorId } );
-	};
-
-	/**
-	 * Handle user input.
-	 *
-	 * @param {string} inputValue The current value of the input field.
-	 */
-	const handleKeydown = ( inputValue ) => {
-		setFieldValue( inputValue );
-	};
-
-	if ( ! postAuthor ) {
-		return null;
+	if ( showCombobox ) {
+		return <PostAuthorCombobox />;
 	}
-
-	return (
-		<PostAuthorCheck>
-			<ComboboxControl
-				label={ __( 'Author' ) }
-				options={ authorOptions }
-				value={ authorId }
-				onFilterValueChange={ debounce( handleKeydown, 300 ) }
-				onChange={ handleSelect }
-				isLoading={ isLoading }
-				allowReset={ false }
-			/>
-		</PostAuthorCheck>
-	);
+	return <PostAuthorSelect />;
 }
 
 export default PostAuthor;

packages/editor/src/components/post-author/select.js

@@ -0,0 +1,40 @@
+/**
+ * WordPress dependencies
+ */
+import { __ } from '@wordpress/i18n';
+import { useSelect, useDispatch } from '@wordpress/data';
+import { decodeEntities } from '@wordpress/html-entities';
+import { SelectControl } from '@wordpress/components';
+
+function PostAuthorSelect() {
+	const { editPost } = useDispatch( 'core/editor' );
+	const { postAuthor, authors } = useSelect( ( select ) => {
+		const authorsFromAPI = select( 'core' ).getAuthors();
+		return {
+			postAuthor: select( 'core/editor' ).getEditedPostAttribute(
+				'author'
+			),
+			authors: authorsFromAPI.map( ( author ) => ( {
+				label: decodeEntities( author.name ),
+				value: author.id,
+			} ) ),
+		};
+	}, [] );
+
+	const setAuthorId = ( value ) => {
+		const author = Number( value );
+		editPost( { author } );
+	};
+
+	return (
+		<SelectControl
+			className="post-author-selector"
+			label={ __( 'Author' ) }
+			options={ authors }
+			onChange={ setAuthorId }
+			value={ postAuthor }
+		/>
+	);
+}
+
+export default PostAuthorSelect;