Allowing jest to ingest typescript files

.gitignore

@@ -1,2 +1,3 @@
-*.js
-node_modules
+/node_modules/
+/lib/**/*.js
+index.js

babel.config.js

@@ -0,0 +1,6 @@
+module.exports = {
+  presets: [
+    ['@babel/preset-env', {targets: {node: 'current'}}],
+    '@babel/preset-typescript',
+  ]
+};

lib/__tests__/convertCssForEmotion.test.ts

@@ -115,53 +115,6 @@ select.form-control:not([size]):not([multiple]) {
 
     const cssForEmotion = `import { css, injectGlobal } from "emotion";
 
-injectGlobal\`*, *::before, *::after {
-    box-sizing: inherit;
-}
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-@-ms-viewport {
-    width: device-width;
-}
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-\`;
-
 export const close = css\`
     float: right;
     font-size: 1.5rem;
@@ -281,6 +234,53 @@ export const formControl = css\`select&:not([size]):not([multiple]) {
     color: #868e96;
     opacity: 1;
 }
+
+\`;
+
+injectGlobal\`*, *::before, *::after {
+    box-sizing: inherit;
+}
+
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+@-ms-viewport {
+    width: device-width;
+}
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 \`;
 `;

lib/convertCssForEmotion.ts

@@ -33,7 +33,7 @@ export function convertCssForEmotion(css: string): string {
 
             return collator.compare(scopeA, scopeB);
         })
-        .reduce((previousSortedKnownScopes: Set<string>, knownScope) => {
+        .reduce((previousSortedKnownScopes: Set<string>, knownScope: string) => {
             getRequiredScopes(
                 cssIndexedByScope.get(knownScope) as string,
                 knownScope,

lib/getNodeScopes.ts

@@ -3,7 +3,7 @@ import * as postcss from "postcss";
 import { getSelectorScope } from "./getSelectorScope";
 
 export function getNodeScopes(node: postcss.Node): Set<string> {
-    const nodeScopes = new Set();
+    const nodeScopes: Set<string> = new Set();
 
     if (
         node.type === "rule" &&

lib/getRequiredScopes.ts

@@ -8,7 +8,7 @@ export function getRequiredScopes(
     scope: string,
     knownScopes: Set<string>,
 ): Set<string> {
-    const requiredScopes = new Set();
+    const requiredScopes: Set<string> = new Set();
 
     const root = postcss.parse(css);
     root.walkRules((rule) => {