[Fix] homedir: fix operator precedence bug with HOMEDRIVE/HOMEPATH concatenation

Author: ljharb

lib/homedir.js

@@ -9,7 +9,14 @@ module.exports = os.homedir || function homedir() {
     var user = process.env.LOGNAME || process.env.USER || process.env.LNAME || process.env.USERNAME;
 
     if (process.platform === 'win32') {
-        return process.env.USERPROFILE || process.env.HOMEDRIVE + process.env.HOMEPATH || home || null;
+        return process.env.USERPROFILE
+            || (
+                process.env.HOMEDRIVE
+                && process.env.HOMEPATH
+                && (process.env.HOMEDRIVE + process.env.HOMEPATH)
+            )
+            || home
+            || null;
     }
 
     if (process.platform === 'darwin') {

test/homedir.js

@@ -0,0 +1,95 @@
+'use strict';
+
+var os = require('os');
+var test = require('tape');
+var mockProperty = require('mock-property');
+
+var envKeys = ['HOME', 'USERPROFILE', 'HOMEDRIVE', 'HOMEPATH', 'LOGNAME', 'USER', 'LNAME', 'USERNAME'];
+
+function clearEnv(t) {
+    for (var i = 0; i < envKeys.length; i++) {
+        t.teardown(mockProperty(process.env, envKeys[i], { 'delete': true }));
+    }
+}
+
+function getFallback(t) {
+    t.teardown(mockProperty(os, 'homedir', { value: undefined }));
+
+    var homedirPath = require.resolve('../lib/homedir');
+    t.teardown(mockProperty(require.cache, homedirPath, { 'delete': true }));
+
+    return require('../lib/homedir');
+}
+
+test('homedir fallback', function (t) {
+    t.test('win32: HOMEDRIVE without HOMEPATH does not produce a false concatenation', function (st) {
+        clearEnv(st);
+        st.teardown(mockProperty(process, 'platform', { value: 'win32' }));
+
+        var homedir = getFallback(st);
+
+        st.teardown(mockProperty(process.env, 'HOMEDRIVE', { value: 'C:' }));
+
+        st.equal(homedir(), null, 'returns null when only HOMEDRIVE is set');
+
+        st.end();
+    });
+
+    t.test('win32: HOMEPATH without HOMEDRIVE does not produce a false concatenation', function (st) {
+        clearEnv(st);
+        st.teardown(mockProperty(process, 'platform', { value: 'win32' }));
+
+        var homedir = getFallback(st);
+
+        st.teardown(mockProperty(process.env, 'HOMEPATH', { value: '\\Users\\foo' }));
+
+        st.equal(homedir(), null, 'returns null when only HOMEPATH is set');
+
+        st.end();
+    });
+
+    t.test('win32: HOMEDRIVE + HOMEPATH both set returns concatenation', function (st) {
+        clearEnv(st);
+        st.teardown(mockProperty(process, 'platform', { value: 'win32' }));
+
+        var homedir = getFallback(st);
+
+        st.teardown(mockProperty(process.env, 'HOMEDRIVE', { value: 'C:' }));
+        st.teardown(mockProperty(process.env, 'HOMEPATH', { value: '\\Users\\foo' }));
+
+        st.equal(homedir(), 'C:\\Users\\foo', 'returns concatenated drive and path');
+
+        st.end();
+    });
+
+    t.test('win32: USERPROFILE takes precedence over HOMEDRIVE+HOMEPATH', function (st) {
+        clearEnv(st);
+        st.teardown(mockProperty(process, 'platform', { value: 'win32' }));
+
+        var homedir = getFallback(st);
+
+        st.teardown(mockProperty(process.env, 'USERPROFILE', { value: 'C:\\Users\\bar' }));
+        st.teardown(mockProperty(process.env, 'HOMEDRIVE', { value: 'C:' }));
+        st.teardown(mockProperty(process.env, 'HOMEPATH', { value: '\\Users\\foo' }));
+
+        st.equal(homedir(), 'C:\\Users\\bar', 'returns USERPROFILE');
+
+        st.end();
+    });
+
+    t.test('win32: falls back to HOME when HOMEDRIVE/HOMEPATH are partial', function (st) {
+        clearEnv(st);
+        st.teardown(mockProperty(process, 'platform', { value: 'win32' }));
+
+        var homedir = getFallback(st);
+
+        st.teardown(mockProperty(process.env, 'HOME', { value: 'C:\\Users\\baz' }));
+        st.teardown(mockProperty(process.env, 'HOMEDRIVE', { value: 'C:' }));
+
+        st.equal(homedir(), 'C:\\Users\\baz', 'falls back to HOME');
+
+        st.end();
+    });
+
+    t.end();
+});