Fix unwanted additional spaces added around pasted text on Windows (#…

…33607)

* Remove the whitespace before the fragments that are provided by windows

See https://discuss.prosemirror.net/t/space-added-on-paste/1274/7

* Extract to util

* Avoid creating public APIs for util and improve function naming for clarity

As we're not sure about this fix let's not create a public API via utils. Instead revert to inlining.

Also renaming the function to make it's purpose clearer. It's not a generic normalizing function so let's make it obvious this is Windows specific.

* Make both regexes literal

packages/block-editor/src/components/rich-text/use-paste-handler.js

@@ -69,6 +69,9 @@ export function usePasteHandler( props ) {
 				}
 			}
 
+			// Remove Windows-specific metadata appended within copied HTML text.
+			html = removeWindowsFragments( html );
+
 			event.preventDefault();
 
 			// Allows us to ask for this information when we get a report.
@@ -222,3 +225,17 @@ export function usePasteHandler( props ) {
 		};
 	}, [] );
 }
+
+/**
+ * Normalizes a given string of HTML to remove the Windows specific "Fragment" comments
+ * and any preceeding and trailing whitespace.
+ *
+ * @param {string} html the html to be normalized
+ * @return {string} the normalized html
+ */
+function removeWindowsFragments( html ) {
+	const startReg = /.*<!--StartFragment-->/s;
+	const endReg = /<!--EndFragment-->.*/s;
+
+	return html.replace( startReg, '' ).replace( endReg, '' );
+}