From a98c1c9078f62a8e77da1ca7eae3bb10deaaa0e1 Mon Sep 17 00:00:00 2001
From: Krishna Rajendran <krishna@emptybox.org>
Date: Wed, 30 Sep 2015 02:16:06 -0700
Subject: [PATCH] Support variable expansion in the middle of a string.

Allow basic variable expansion in the middle of a string.

Here is an example use case:

```
$DB_USER=my_user
$DB_HOST=localhost
$DB_NAME=my_db

$DATABASE_URL="${DB_USER}@${DB_HOST}/${DB_NAME}"
```
---
 lib/main.js  | 33 +++++++++++++++++++++++++--------
 test/.env    |  5 +++++
 test/main.js | 25 +++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 8 deletions(-)

diff --git a/lib/main.js b/lib/main.js
index 4643d658..87873f2c 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -67,17 +67,34 @@ module.exports = {
           value = value.replace(/\\n/gm, '\n')
         }
 
+        var isSingleQuoted = value.charAt(0) === '\'' && value.charAt(len - 1) === '\''
+
         // remove any surrounding quotes and extra spaces
         value = value.replace(/(^['"]|['"]$)/g, '').trim()
 
-        // is this value a variable?
-        if (value.charAt(0) === '$') {
-          var possibleVar = value.substring(1)
-          value = obj[possibleVar] || process.env[possibleVar] || ''
-        }
-        // varaible can be escaped with a \$
-        if (value.substring(0, 2) === '\\$') {
-          value = value.substring(1)
+        // match and replace variables
+        if (!isSingleQuoted) {
+          value = value.replace(/\\?\${?[^}]*}?/g, function (match) {
+            var possibleVar
+            var len = match.length
+
+            // variable can be escaped with a \$
+            if (match.charAt(0) === '\\') {
+              return match.substring(1)
+            }
+
+            if (match.charAt(1) === '{') {
+              // if there is an opening brace there must be a closing one
+              if (match.charAt(len - 1) !== '}') {
+                return match
+              }
+              possibleVar = match.slice(2, -1)
+            } else {
+              possibleVar = match.substring(1)
+            }
+
+            return obj[possibleVar] || process.env[possibleVar] || ''
+          })
         }
 
         obj[key] = value
diff --git a/test/.env b/test/.env
index 22201c89..17ee7695 100644
--- a/test/.env
+++ b/test/.env
@@ -17,3 +17,8 @@ EQUAL_SIGNS=equals==
 RETAIN_INNER_QUOTES={"foo": "bar"}
 RETAIN_INNER_QUOTES_AS_STRING='{"foo": "bar"}'
 INCLUDE_SPACE=some spaced out string
+BRACED_EXPAND=${BASIC}
+INLINE_EXPAND="inline${BASIC}ally"
+ESCAPED_INLINE_EXPAND="inline\${BASIC}ally"
+SINGLE_QUOTED_INLINE_EXPAND='inline${BASIC}ally'
+UNCLOSED_INLINE_EXPAND="inline${BASICally"
diff --git a/test/main.js b/test/main.js
index dcfbe632..04761574 100644
--- a/test/main.js
+++ b/test/main.js
@@ -155,6 +155,31 @@ describe('dotenv', function () {
         parsed.ESCAPED_EXPAND.should.equal('$ESCAPED')
         done()
       })
+
+      it('expands variables surrounded by braces', function (done) {
+        parsed.SINGLE_QUOTED_INLINE_EXPAND.should.equal('inline${BASIC}ally')
+        done()
+      })
+
+      it('expands inline environment variables', function (done) {
+        parsed.INLINE_EXPAND.should.equal('inlinebasically')
+        done()
+      })
+
+      it('does not expands inline escaped variables', function (done) {
+        parsed.ESCAPED_INLINE_EXPAND.should.equal('inline${BASIC}ally')
+        done()
+      })
+
+      it('does not expands inline variables in single quoted strings', function (done) {
+        parsed.SINGLE_QUOTED_INLINE_EXPAND.should.equal('inline${BASIC}ally')
+        done()
+      })
+
+      it('does not expands inline variables with unclosed braces', function (done) {
+        parsed.UNCLOSED_INLINE_EXPAND.should.equal('inline${BASICally')
+        done()
+      })
     })
 
     it('defaults empty values to empty string', function (done) {