[gnome-code-assistance] Add a pyflakes check to the Python backend

[Elad Alfassa <eladalfassa src gnome org>]

commit 4176c4f4eaeab7f8f64842e4d879871720a4b39b
Author: Luke Benstead <kazade gmail com>
Date:   Wed Mar 8 13:39:19 2017 +0000

    Add a pyflakes check to the Python backend
    
    https://bugzilla.gnome.org/show_bug.cgi?id=779752

 README                      |    2 +-
 backends/python/__init__.py |   60 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 1 deletions(-)
---
diff --git a/README b/README
index 9c9e341..475b5c3 100644
--- a/README
+++ b/README
@@ -185,7 +185,7 @@ Dependencies : python, python-dbus, python-simplejson
 
 ### Python
 Dependencies : python, python-dbus
-Optional dependencies : pylint (enabled only if you will pass "pylint" in "options" to dbus service), pep8 
(run when present)
+Optional dependencies : pylint (enabled only if you will pass "pylint" in "options" to dbus service), pep8 
(run when present), pyflakes (enabled when present)
 
 ### Ruby
 Dependencies : ruby, ruby-dbus
diff --git a/backends/python/__init__.py b/backends/python/__init__.py
index 7694dd8..7776614 100644
--- a/backends/python/__init__.py
+++ b/backends/python/__init__.py
@@ -2,6 +2,7 @@
 # Copyright (C) 2013  Jesse van den Kieboom <jessevdk gnome org>
 # Copyright (C) 2014  Elad Alfassa <elad fedoraproject org>
 # Copyright (C) 2015  Igor Gnatenko <ignatenko src gnome org>
+# Copyright (C) 2017  Luke Benstead <kazade gmail com>
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -28,6 +29,13 @@ try:
 except ImportError:
     HAS_PYLINT = False
 
+try:
+    from pyflakes.api import checkPath as pyflakes_check
+    from pyflakes.reporter import Reporter
+    HAS_PYFLAKES = True
+except ImportError:
+    HAS_PYFLAKES = False
+
 from gnome.codeassistance import transport, types
 
 class PyLint(object):
@@ -66,6 +74,52 @@ class PyLint(object):
         return self.diagnostics
 
 
+class Pyflakes(object):
+    def __init__(self, data_path):
+        self.data_path = data_path
+
+    def run(self):
+
+        class PyflakesReporter(Reporter):
+            """
+                Custom reporter, nested as parent class will not have been imported
+                if pyflakes wasn't available
+            """
+            def __init__(self):
+                self.diagnostics = []
+
+            def unexpectedError(self, filename, msg):
+                loc = types.SourceLocation(line=0, column=0)
+                severity = types.Diagnostic.Severity.ERROR
+                self.diagnostics.append(
+                    types.Diagnostic(severity=severity,
+                                     locations=[loc.to_range()],
+                                     message=str(msg)))
+
+            def syntaxError(self, filename, msg, lineno, offset, text):
+                severity = types.Diagnostic.Severity.ERROR
+                col = int(offset) + 1
+                loc = types.SourceLocation(line=lineno, column=col)
+                self.diagnostics.append(
+                    types.Diagnostic(severity=severity,
+                                     locations=[loc.to_range()],
+                                     message=str(msg)))
+
+            def flake(self, message):
+                loc = types.SourceLocation(line=message.lineno,
+                                           column=int(message.col) + 1)
+                severity = types.Diagnostic.Severity.WARNING
+                text = message.message % message.message_args
+                self.diagnostics.append(
+                    types.Diagnostic(severity=severity,
+                                     locations=[loc.to_range()],
+                                     message=text))
+
+        reporter = PyflakesReporter()
+        pyflakes_check(self.data_path, reporter=reporter)
+        return reporter.diagnostics
+
+
 class Service(transport.Service):
     language = 'python'
 
@@ -105,6 +159,12 @@ class Service(transport.Service):
             for diag in diagnostics:
                 doc.diagnostics.append(diag)
 
+        if HAS_PYFLAKES:
+            pyflakes = Pyflakes(doc.data_path)
+            diagnostics = pyflakes.run()
+            for diag in diagnostics:
+                doc.diagnostics.append(diag)
+
 
 class Document(transport.Document, transport.Diagnostics):
     pass