fix: Resolve value of env variables before invoking cross-spawn

kentcdodds#90

src/index.js

@@ -26,9 +26,9 @@ function crossEnv(args) {
 
 function getCommandArgsAndEnvVars(args) {
   const envVars = getEnvVars()
-  const commandArgs = args.map(commandConvert)
-  const command = getCommand(commandArgs, envVars)
-  return [command, commandArgs, envVars]
+  const commandArgs = args.slice()
+  const command = commandConvert(getCommand(commandArgs, envVars))
+  return [commandConvert(command), commandArgs.map(commandConvert), envVars]
 }
 
 function getCommand(commandArgs, envVars) {

src/variable.js

@@ -1,16 +1,15 @@
 import isWindows from 'is-windows'
 
 /**
- * Converts an environment variable value to be appropriate for the current OS.
- * It will transform UNIX-style list values to Windows-style.
+ * This will transform UNIX-style list values to Windows-style.
  * For example, the value of the $PATH variable "/usr/bin:/usr/local/bin:."
  * will become "/usr/bin;/usr/local/bin;." on Windows.
- * @param {String} originalValue Original value of the env variable
+ * @param {String} varValue Original value of the env variable
  * @returns {String} Converted value
  */
-export default function varValueConvert(originalValue) {
+function replaceListDelimiters(varValue) {
   const targetSeparator = isWindows() ? ';' : ':'
-  return originalValue.replace(/(\\*):/g, (match, backslashes) => {
+  return varValue.replace(/(\\*):/g, (match, backslashes) => {
     if (backslashes.length % 2) {
       // Odd number of backslashes preceding it means it's escaped,
       // remove 1 backslash and return the rest as-is
@@ -19,3 +18,32 @@ export default function varValueConvert(originalValue) {
     return backslashes + targetSeparator
   })
 }
+
+/**
+ * This will attempt to resolve the value of any env variables that are inside
+ * this string. For example, it will transform this:
+ * cross-env FOO=$NODE_ENV echo $FOO
+ * Into this:
+ * FOO=development echo $FOO
+ * (Or whatever value the variable NODE_ENV has)
+ * Note that this function is only called with the right-side portion of the
+ * env var assignment, so in that example, this function would transform
+ * the string "$NODE_ENV" into "development"
+ * @param {String} varValue Original value of the env variable
+ * @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] || ''
+  })
+}
+
+/**
+ * Converts an environment variable value to be appropriate for the current OS.
+ * @param {String} originalValue Original value of the env variable
+ * @returns {String} Converted value
+ */
+export default function varValueConvert(originalValue) {
+  return resolveEnvVars(replaceListDelimiters(originalValue))
+}

src/variable.test.js

@@ -2,9 +2,16 @@ import isWindowsMock from 'is-windows'
 import varValueConvert from './variable'
 
 beforeEach(() => {
+  process.env.VAR1 = 'value1'
+  process.env.VAR2 = 'value2'
   isWindowsMock.__mock.reset()
 })
 
+afterEach(() => {
+  delete process.env.VAR1
+  delete process.env.VAR2
+})
+
 test(`doesn't affect simple variable values`, () => {
   isWindowsMock.__mock.returnValue = true
   expect(varValueConvert('foo')).toBe('foo')
@@ -44,3 +51,24 @@ test(`converts multiple separators`, () => {
   isWindowsMock.__mock.returnValue = true
   expect(varValueConvert('foo:bar:baz')).toBe('foo;bar;baz')
 })
+
+test(`resolves an env variable value`, () => {
+  isWindowsMock.__mock.returnValue = true
+  expect(varValueConvert('foo-$VAR1')).toBe('foo-value1')
+})
+
+test(`resolves an env variable value with curly syntax`, () => {
+  isWindowsMock.__mock.returnValue = true
+  // eslint-disable-next-line no-template-curly-in-string
+  expect(varValueConvert('foo-${VAR1}')).toBe('foo-value1')
+})
+
+test(`resolves multiple env variable values`, () => {
+  isWindowsMock.__mock.returnValue = true
+  expect(varValueConvert('foo-$VAR1-$VAR2')).toBe('foo-value1-value2')
+})
+
+test(`resolves an env variable value for non-existant variable`, () => {
+  isWindowsMock.__mock.returnValue = true
+  expect(varValueConvert('foo-$VAR_POTATO')).toBe('foo-')
+})