Support escaping template variables

Author: parksb

packages/yarnpkg-core/sources/miscUtils.ts

@@ -469,11 +469,13 @@ export function buildIgnorePattern(ignorePatterns: Array<string>) {
 }
 
 export function replaceEnvVariables(value: string, {env}: {env: {[key: string]: string | undefined}}) {
-  const regex = /\${(?<variableName>[\d\w_]+)(?<colon>:)?(?:-(?<fallback>[^}]*))?}/g;
+  const regex = /\\?\${(?<variableName>[\d\w_]+)(?<colon>:)?(?:-(?<fallback>[^}]*))?}/g;
 
-  return value.replace(regex, (...args) => {
-    const {variableName, colon, fallback} = args[args.length - 1];
+  return value.replace(regex, (match, ...args) => {
+    if (match.startsWith(`\\`))
+      return match.slice(1);
 
+    const {variableName, colon, fallback} = args[args.length - 1];
     const variableExist = Object.hasOwn(env, variableName);
     const variableValue = env[variableName];
 

packages/yarnpkg-core/tests/miscUtils.test.ts

@@ -26,6 +26,20 @@ describe(`miscUtils`, () => {
         ),
       ).toBe(`VAR_A: ValueA, VAR_B: ValueB`);
     });
+
+    it(`should not replace escaped environment variables`, () => {
+      expect(
+        miscUtils.replaceEnvVariables(
+          `VAR_A: \\\${VAR_A}, VAR_B: \\\${VAR_B}`,
+          {
+            env: {
+              VAR_A: `ValueA`,
+              VAR_B: `ValueB`,
+            },
+          },
+        ),
+      ).toBe(`VAR_A: \${VAR_A}, VAR_B: \${VAR_B}`);
+    });
   });
 
   describe(`mapAndFind`, () => {