feat: introduce dollar sign escaping (#147)

* Introduce dollar sign escaping

* Fix typo in README.md

Author: Sven

.all-contributorsrc

@@ -142,6 +142,18 @@
         "code",
         "test"
       ]
+    },
+    {
+      "login": "sventschui",
+      "name": "Sven",
+      "avatar_url": "https://avatars3.githubusercontent.com/u/512692?v=4",
+      "profile": "https://github.com/sventschui",
+      "contributions": [
+        "code",
+        "doc",
+        "example",
+        "test"
+      ]
     }
   ]
 }

README.md

@@ -16,7 +16,7 @@ Run scripts that set and use environment variables across platforms
 [![downloads][downloads-badge]][npm-stat]
 
 [![MIT License][license-badge]][LICENSE]
-[![All Contributors](https://img.shields.io/badge/all_contributors-13-orange.svg?style=flat-square)](#contributors)
+[![All Contributors](https://img.shields.io/badge/all_contributors-14-orange.svg?style=flat-square)](#contributors)
 [![PRs Welcome][prs-badge]][prs]
 [![Donate][donate-badge]][donate]
 [![Code of Conduct][coc-badge]][coc]
@@ -97,6 +97,8 @@ the parent. This is quite useful for launching the same command with different
 env variables or when the environment variables are too long to have everything
 in one line.
 
+If you preceed a dollar sign with an odd number of backslashes the expression statement will not be replaced. Note that this means backslashes after the JSON string escaping took place. `"FOO=\\$BAR"` will not be replaced. `"FOO=\\\\$BAR"` will be replaced though.
+
 Lastly, if you want to pass a JSON string (e.g., when using [ts-loader]), you can do as follows:
 
 ```json
@@ -151,9 +153,9 @@ much easier for Windows users.
 Thanks goes to these people ([emoji key][emojis]):
 
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-| [<img src="https://avatars0.githubusercontent.com/u/3715715?v=3" width="100px;"/><br /><sub>Thiebaud Thomas</sub>](https://github.com/thomasthiebaud)<br />[🐛](https://github.com/kentcdodds/cross-env/issues?q=author%3Athomasthiebaud) [💻](https://github.com/kentcdodds/cross-env/commits?author=thomasthiebaud) [⚠️](https://github.com/kentcdodds/cross-env/commits?author=thomasthiebaud) | [<img src="https://avatars1.githubusercontent.com/u/1715800?v=3" width="100px;"/><br /><sub>Daniel Rey López</sub>](https://daniel.blog)<br />[💻](https://github.com/kentcdodds/cross-env/commits?author=DanReyLop) [⚠️](https://github.com/kentcdodds/cross-env/commits?author=DanReyLop) | [<img src="https://avatars2.githubusercontent.com/u/6374832?v=3" width="100px;"/><br /><sub>Amila Welihinda</sub>](http://amilajack.com)<br />🚇 | [<img src="https://avatars1.githubusercontent.com/u/1396?v=3" width="100px;"/><br /><sub>Paul Betts</sub>](https://twitter.com/paulcbetts)<br />[🐛](https://github.com/kentcdodds/cross-env/issues?q=author%3Apaulcbetts) [💻](https://github.com/kentcdodds/cross-env/commits?author=paulcbetts) | [<img src="https://avatars1.githubusercontent.com/u/6371670?v=3" width="100px;"/><br /><sub>Turner Hayes</sub>](https://github.com/turnerhayes)<br />[🐛](https://github.com/kentcdodds/cross-env/issues?q=author%3Aturnerhayes) [💻](https://github.com/kentcdodds/cross-env/commits?author=turnerhayes) [⚠️](https://github.com/kentcdodds/cross-env/commits?author=turnerhayes) | [<img src="https://avatars2.githubusercontent.com/u/22251956?v=4" width="100px;"/><br /><sub>Suhas Karanth</sub>](https://github.com/sudo-suhas)<br />[💻](https://github.com/kentcdodds/cross-env/commits?author=sudo-suhas) [⚠️](https://github.com/kentcdodds/cross-env/commits?author=sudo-suhas) |
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 <!-- ALL-CONTRIBUTORS-LIST:END -->
 
 This project follows the [all-contributors][all-contributors] specification. Contributions of any kind welcome!

src/__tests__/variable.js

@@ -97,3 +97,23 @@ test(`resolves an env variable with a JSON string value on UNIX`, () => {
   isWindowsMock.__mock.returnValue = false
   expect(varValueConvert('$JSON_VAR')).toBe(JSON_VALUE)
 })
+
+test(`does not resolve an env variable prefixed with \\ on Windows`, () => {
+  isWindowsMock.__mock.returnValue = true
+  expect(varValueConvert('\\$VAR1')).toBe('$VAR1')
+})
+
+test(`does not resolve an env variable prefixed with \\ on UNIX`, () => {
+  isWindowsMock.__mock.returnValue = false
+  expect(varValueConvert('\\$VAR1')).toBe('$VAR1')
+})
+
+test(`resolves an env variable prefixed with \\\\ on Windows`, () => {
+  isWindowsMock.__mock.returnValue = true
+  expect(varValueConvert('\\\\$VAR1')).toBe('\\value1')
+})
+
+test(`resolves an env variable prefixed with \\\\ on UNIX`, () => {
+  isWindowsMock.__mock.returnValue = false
+  expect(varValueConvert('\\\\$VAR1')).toBe('\\value1')
+})

src/variable.js

@@ -29,9 +29,9 @@ function replaceListDelimiters(varValue, varName = '') {
 /**
  * This will attempt to resolve the value of any env variables that are inside
  * this string. For example, it will transform this:
- * cross-env FOO=$NODE_ENV echo $FOO
+ * cross-env FOO=$NODE_ENV BAR=\\$NODE_ENV echo $FOO $BAR
  * Into this:
- * FOO=development echo $FOO
+ * FOO=development BAR=$NODE_ENV echo $FOO
  * (Or whatever value the variable NODE_ENV has)
  * Note that this function is only called with the right-side portion of the
  * env var assignment, so in that example, this function would transform
@@ -40,10 +40,20 @@ function replaceListDelimiters(varValue, varName = '') {
  * @returns {String} Converted value
  */
 function resolveEnvVars(varValue) {
-  const envUnixRegex = /\$(\w+)|\${(\w+)}/g // $my_var or ${my_var}
-  return varValue.replace(envUnixRegex, (_, varName, altVarName) => {
-    return process.env[varName || altVarName] || ''
-  })
+  const envUnixRegex = /(\\*)(\$(\w+)|\${(\w+)})/g // $my_var or ${my_var} or \$my_var
+  return varValue.replace(
+    envUnixRegex,
+    (_, escapeChars, varNameWithDollarSign, varName, altVarName) => {
+      // do not replace things preceded by a odd number of \
+      if (escapeChars.length % 2 === 1) {
+        return varNameWithDollarSign
+      }
+      return (
+        escapeChars.substr(0, escapeChars.length / 2) +
+        (process.env[varName || altVarName] || '')
+      )
+    },
+  )
 }
 
 /**