python: more informative error

PR-URL: #1269
Refs: #1582
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: João Reis <reis@janeasystems.com>

.eslintrc.yaml

@@ -1,5 +1,6 @@
 ---
   env:
     node: true
+    es6: true
   rules:
     no-unused-vars: error

.jshintrc

@@ -1,7 +1,7 @@
 {
   "asi": true,
   "laxcomma": true,
-  "es5": true,
+  "esversion": 6,
   "node": true,
   "strict": false
 }

bin/node-gyp.js

@@ -79,8 +79,12 @@ function run () {
   prog.commands[command.name](command.args, function (err) {
     if (err) {
       log.error(command.name + ' error')
-      log.error('stack', err.stack)
-      errorMessage()
+      if (err.noPython) {
+        log.error(err.message)
+      } else {
+        log.error('stack', err.stack)
+        errorMessage()
+      }
       log.error('not ok')
       return process.exit(1)
     }

lib/configure.js

@@ -449,7 +449,7 @@ PythonFinder.prototype = {
                        '`%s -c "' + args[1] + '"` returned: %j',
                        this.python, stdout)
       var version = stdout.trim()
-      var range = semver.Range('>=2.5.0 <3.0.0')
+      var range = semver.Range('>=2.6.0 <3.0.0')
       var valid = false
       try {
         valid = range.test(version)
@@ -467,19 +467,32 @@ PythonFinder.prototype = {
   },
 
   failNoPython: function failNoPython () {
-    var errmsg =
-        'Can\'t find Python executable "' + this.python +
-        '", you can set the PYTHON env variable.'
-    this.callback(new Error(errmsg))
+    const err = new Error(
+      '\n******************************************************************\n' +
+      `node-gyp can't use "${this.python}",\n` +
+      'It is recommended that you install python 2.7, set the PYTHON env,\n' +
+      'or use the --python switch to point to a Python >= v2.6.0 & < 3.0.0.\n' +
+      'For more information consult the documentation at:\n' +
+      'https://github.com/nodejs/node-gyp#installation\n' +
+      '***********************************************************************'
+    );
+    err.noPython = true;
+    this.callback(err)
   },
 
   failPythonVersion: function failPythonVersion (badVersion) {
-    var errmsg =
-        'Python executable "' + this.python +
-        '" is v' + badVersion + ', which is not supported by gyp.\n' +
-        'You can pass the --python switch to point to ' +
-        'Python >= v2.5.0 & < 3.0.0.'
-    this.callback(new Error(errmsg))
+    const err = new Error(
+      '\n******************************************************************\n' +
+      `Python executable "${this.python}" is v${badVersion}\n` +
+      'this version is not supported by GYP and hence by node-gyp.\n' +
+      'It is recommended that you install python 2.7, set the PYTHON env,\n' +
+      'or use the --python switch to point to a Python >= v2.6.0 & < 3.0.0.\n' +
+      'For more information consult the documentation at:\n' +
+      'https://github.com/nodejs/node-gyp#installation\n' +
+      '***********************************************************************'
+    );
+    err.noPython = true;
+    this.callback(err)
   },
 
   // Called on Windows when "python" isn't available in the current $PATH.

test/test-find-python.js

@@ -74,7 +74,7 @@ test('find python - python', function (t) {
 })
 
 test('find python - python too old', function (t) {
-  t.plan(4)
+  t.plan(5)
 
   var f = new TestPythonFinder('python', done)
   f.which = function(program, cb) {
@@ -89,12 +89,13 @@ test('find python - python too old', function (t) {
   f.checkPython()
 
   function done(err) {
-    t.ok(/is not supported by gyp/.test(err))
+    t.ok(/this version is not supported by GYP/.test(err))
+    t.ok(/For more information consult the documentation/.test(err))
   }
 })
 
 test('find python - python too new', function (t) {
-  t.plan(4)
+  t.plan(5)
 
   var f = new TestPythonFinder('python', done)
   f.which = function(program, cb) {
@@ -109,7 +110,8 @@ test('find python - python too new', function (t) {
   f.checkPython()
 
   function done(err) {
-    t.ok(/is not supported by gyp/.test(err))
+    t.ok(/this version is not supported by GYP/.test(err))
+    t.ok(/For more information consult the documentation/.test(err))
   }
 })
 
@@ -124,7 +126,7 @@ test('find python - no python', function (t) {
   f.checkPython()
 
   function done(err) {
-    t.ok(/Can't find Python executable/.test(err))
+    t.ok(/For more information consult the documentation/.test(err))
   }
 })
 
@@ -171,7 +173,7 @@ test('find python - no python2, no python, unix', function (t) {
   f.checkPython()
 
   function done(err) {
-    t.ok(/Can't find Python executable/.test(err))
+    t.ok(/For more information consult the documentation/.test(err))
   }
 })
 
@@ -242,7 +244,7 @@ test('find python - python 3, use python launcher', function (t) {
 
 test('find python - python 3, use python launcher, python 2 too old',
      function (t) {
-  t.plan(9)
+  t.plan(10)
 
   var f = new TestPythonFinder('python', done)
   f.checkedPythonLauncher = false
@@ -272,7 +274,8 @@ test('find python - python 3, use python launcher, python 2 too old',
   f.checkPython()
 
   function done(err) {
-    t.ok(/is not supported by gyp/.test(err))
+    t.ok(/this version is not supported by GYP/.test(err))
+    t.ok(/For more information consult the documentation/.test(err))
   }
 })
 
@@ -334,6 +337,6 @@ test('find python - no python, no python launcher, bad guess', function (t) {
   f.checkPython()
 
   function done(err) {
-    t.ok(/Can't find Python executable/.test(err))
+    t.ok(/For more information consult the documentation/.test(err))
   }
 })