#130 fixing stderr causing python-shell to emit error

Author: Almenon

index.ts

@@ -145,7 +145,7 @@ export class PythonShell extends EventEmitter{
             if(!self.stderrHasEnded || !self.stdoutHasEnded || (self.exitCode == null && self.exitSignal == null)) return;
 
             let err:PythonShellError;
-            if (errorData || (self.exitCode && self.exitCode !== 0)) {
+            if (self.exitCode && self.exitCode !== 0) {
                 if (errorData) {
                     err = self.parseError(errorData);
                 } else {

test/python/stderrLogging.py

@@ -0,0 +1,26 @@
+# logging example taken from https://docs.python.org/3/howto/logging-cookbook.html
+# Note that logging logs to stderr by default
+
+import logging
+
+# set up logging to file - see previous section for more details
+logging.basicConfig(level=logging.DEBUG)
+# define a Handler which writes INFO messages or higher to the sys.stderr
+console = logging.StreamHandler()
+console.setLevel(logging.INFO)
+# add the handler to the root logger
+logging.getLogger('').addHandler(console)
+
+# Now, we can log to the root logger, or any other logger. First the root...
+logging.info('Jackdaws love my big sphinx of quartz.')
+
+# Now, define a couple of other loggers which might represent areas in your
+# application:
+
+logger1 = logging.getLogger('myapp.area1')
+logger2 = logging.getLogger('myapp.area2')
+
+logger1.debug('Quick zephyrs blow, vexing daft Jim.')
+logger1.info('How quickly daft jumping zebras vex.')
+logger2.warning('Jail zesty vixen who grabbed pay from quack.')
+logger2.error('The five boxing wizards jump quickly.')

test/test-python-shell.ts

@@ -296,7 +296,7 @@ describe('PythonShell', function () {
                 done();
             });
         });
-        it('should emit error when error is written to stderr', function (done) {
+        it('should emit error when the program exits because of an unhandled exception', function (done) {
             let pyshell = new PythonShell('error.py');
             pyshell.on('error', function (err) {
                 err.message.should.be.equalOneOf('ZeroDivisionError: integer division or modulo by zero','ZeroDivisionError: division by zero');
@@ -305,6 +305,15 @@ describe('PythonShell', function () {
                 done();
             });
         });
+        it('should NOT emit error when logging is written to stderr', function (done) {
+            let pyshell = new PythonShell('stderrLogging.py');
+            pyshell.on('error', function (err) {
+                done(new Error("an error should not have been raised"));
+            });
+            pyshell.on('close', function(){
+                done();
+            })
+        });
     });
 
     describe('.parseError(data)', function () {