allow syntax highlighting in diffs

scm-ui/ui-components/src/repos/TokenizedDiffView.tsx

@@ -0,0 +1,62 @@
+import React, { FC } from "react";
+import styled from "styled-components";
+// @ts-ignore we have no typings for react-diff-view
+import { Diff, useTokenizeWorker } from "react-diff-view";
+// @ts-ignore we use webpack worker-loader to load the web worker
+import TokenizeWorker from "./Tokenize.worker";
+import { File } from "./DiffTypes";
+
+// styling for the diff tokens
+// this must be aligned with th style, which is used in the SyntaxHighlighter component
+import "highlight.js/styles/arduino-light.css";
+
+const DiffView = styled(Diff)`
+  /* align line numbers */
+  & .diff-gutter {
+    text-align: right;
+  }
+  /* column sizing */
+  > colgroup .diff-gutter-col {
+    width: 3.25rem;
+  }
+  /* prevent following content from moving down */
+  > .diff-gutter:empty:hover::after {
+    font-size: 0.7rem;
+  }
+  /* smaller font size for code */
+  & .diff-line {
+    font-size: 0.75rem;
+  }
+  /* comment padding for sidebyside view */
+  &.split .diff-widget-content .is-indented-line {
+    padding-left: 3.25rem;
+  }
+  /* comment padding for combined view */
+  &.unified .diff-widget-content .is-indented-line {
+    padding-left: 6.5rem;
+  }
+`;
+
+// WebWorker which creates tokens for syntax highlighting
+const tokenize = new TokenizeWorker();
+
+type Props = {
+  file: File;
+  viewType: "split" | "unified";
+  className?: string;
+};
+
+const TokenizedDiffView: FC<Props> = ({ file, viewType, className, children }) => {
+  const { tokens } = useTokenizeWorker(tokenize, {
+    hunks: file.hunks,
+    language: file.language || "text"
+  });
+
+  return (
+    <DiffView className={className} viewType={viewType} tokens={tokens} hunks={file.hunks} diffType={file.type}>
+      {children}
+    </DiffView>
+  );
+};
+
+export default TokenizedDiffView;