Add mypy to CI pipelines and fix errors it raises

.drone.yml

@@ -17,6 +17,7 @@ steps:
   - pip install --default-timeout 60 coveralls && export HAS_COVERALLS=1
   - python setup.py install
   - flake8 --exit-zero rdflib
+  - mypy --show-error-context --show-error-codes test rdflib examples
   - PYTHONWARNINGS=default nosetests --with-timer --timer-top-n 42 --with-coverage --cover-tests --cover-package=rdflib
   - coverage report
 
@@ -38,6 +39,7 @@ steps:
   - pip install --default-timeout 60 coveralls && export HAS_COVERALLS=1
   - python setup.py install
   - flake8 --exit-zero rdflib
+  - mypy --show-error-context --show-error-codes test rdflib examples
   - PYTHONWARNINGS=default nosetests --with-timer --timer-top-n 42 --with-coverage --cover-tests --cover-package=rdflib
   - coverage report
 
@@ -59,5 +61,6 @@ steps:
   - pip install --default-timeout 60 coveralls && export HAS_COVERALLS=1
   - python setup.py install
   - flake8 --exit-zero rdflib
+  - mypy --show-error-context --show-error-codes test rdflib examples
   - PYTHONWARNINGS=default nosetests --with-timer --timer-top-n 42 --with-coverage --cover-tests --cover-package=rdflib
   - coverage report

.travis.yml

@@ -34,6 +34,7 @@ install:
 
 before_script:
     - flake8 --exit-zero rdflib
+    - mypy --show-error-context --show-error-codes test rdflib examples
 
 script:
     - PYTHONWARNINGS=default nosetests --with-timer --timer-top-n 42 --with-coverage --cover-tests --cover-package=rdflib

examples/conjunctive_graphs.py

@@ -43,17 +43,17 @@
         print("-- %s " % c)
 
     # separate graphs
-    print(gjohn.serialize(format="n3").decode("utf-8"))
+    print(gjohn.serialize(format="n3"))
     print("===================")
-    print(gmary.serialize(format="n3").decode("utf-8"))
+    print(gmary.serialize(format="n3"))
     print("===================")
 
     # full graph
-    print(g.serialize(format="n3").decode("utf-8"))
+    print(g.serialize(format="n3"))
 
     # query the conjunction of all graphs
     xx = None
-    for x in g[mary : ns.loves / ns.hasCuteName]:
+    for x in g[mary : ns.loves / ns.hasCuteName]:  # type: ignore[misc]
         xx = x
     print("Q: Who does Mary love?")
     print("A: Mary loves {}".format(xx))

examples/simple_example.py

@@ -39,21 +39,21 @@
 
     # Serialize as XML
     print("--- start: rdf-xml ---")
-    print(store.serialize(format="pretty-xml").decode("utf-8"))
+    print(store.serialize(format="pretty-xml"))
     print("--- end: rdf-xml ---\n")
 
     # Serialize as Turtle
     print("--- start: turtle ---")
-    print(store.serialize(format="turtle").decode("utf-8"))
+    print(store.serialize(format="turtle"))
     print("--- end: turtle ---\n")
 
     # Serialize as NTriples
     print("--- start: ntriples ---")
-    print(store.serialize(format="nt").decode("utf-8"))
+    print(store.serialize(format="nt"))
     print("--- end: ntriples ---\n")
 
     # Serialize as JSON-LD
     # only if you have the JSON-LD plugin installed!
     print("--- start: JSON-LD ---")
-    print(store.serialize(format="json-ld").decode("utf-8"))
+    print(store.serialize(format="json-ld"))
     print("--- end: JSON-LD ---\n")

examples/sleepycat_example.py

@@ -39,8 +39,6 @@
     # close when done, otherwise sleepycat will leak lock entries.
     graph.close()
 
-    graph = None
-
     # reopen the graph
 
     graph = ConjunctiveGraph("Sleepycat")

examples/smushing.py

@@ -42,4 +42,4 @@
         o = newURI.get(o, o)  # might be linked to another person
         out.add((s, p, o))
 
-    print(out.serialize(format="n3").decode("utf-8"))
+    print(out.serialize(format="n3"))

examples/sparqlstore_example.py

@@ -17,7 +17,7 @@
 
     print(
         "According to DBPedia, Berlin has a population of {0:,}".format(
-            int(pop), ",d"
+            int(pop)
         ).replace(",", ".")
     )
 
@@ -27,7 +27,7 @@
     for p in st.objects(URIRef("http://dbpedia.org/resource/Brisbane"), dbo.populationTotal):
         print(
             "According to DBPedia, Brisbane has a population of "
-            "{0:,}".format(int(pop), ",d")
+            "{0:,}".format(int(pop))
         )
 
     # EXAMPLE 3: doing RDFlib triple navigation using SPARQLStore as a Graph()

examples/swap_primer.py

@@ -124,7 +124,7 @@
 
     print()
     print("Printing bigger example as N3:")
-    print(primer.serialize(format="n3").decode("utf-8"))
+    print(primer.serialize(format="n3"))
 
     # for more insight into things already done, lets see the namespaces
 

mypy.ini

@@ -0,0 +1,6 @@
+# https://mypy.readthedocs.io/en/stable/config_file.html
+[mypy]
+python_version = 3.6
+warn_unused_configs = True
+ignore_missing_imports = True
+disallow_subclassing_any = False

rdflib/compat.py

@@ -6,29 +6,34 @@
 import re
 import codecs
 import warnings
+import typing as t
 
-
-# clean ElementTree import
-try:
-    from lxml import etree
-except ImportError:
+if t.TYPE_CHECKING:
+    import xml.etree.ElementTree as etree
+else:
     try:
-        # Python 2.5
-        import xml.etree.cElementTree as etree
+        from lxml import etree
     except ImportError:
         try:
             # Python 2.5
-            import xml.etree.ElementTree as etree
+            import xml.etree.cElementTree as etree
         except ImportError:
             try:
-                # normal cElementTree install
-                import cElementTree as etree
+                # Python 2.5
+                import xml.etree.ElementTree as etree
             except ImportError:
                 try:
-                    # normal ElementTree install
-                    import elementtree.ElementTree as etree
+                    # normal cElementTree install
+                    import cElementTree as etree
                 except ImportError:
-                    raise Exception("Failed to import ElementTree from any known place")
+                    try:
+                        # normal ElementTree install
+                        import elementtree.ElementTree as etree
+                    except ImportError:
+                        raise Exception(
+                            "Failed to import ElementTree from any known place"
+                        )
+
 
 try:
     etree_register_namespace = etree.register_namespace

rdflib/extras/infixowl.py

@@ -989,7 +989,7 @@ def _get_annotation(self, term=RDFS.label):
         for annotation in self.graph.objects(subject=self, predicate=term):
             yield annotation
 
-    annotation = property(_get_annotation, lambda x: x)
+    annotation = property(_get_annotation, lambda x: x)  # type: ignore[arg-type,misc]
 
     def _get_extentQuery(self):
         return (Variable("CLASS"), RDF.type, self.identifier)
@@ -1496,14 +1496,14 @@ class BooleanClass(OWLRDFListProxy, Class):
 
     @BooleanClassExtentHelper(OWL_NS.intersectionOf)
     @Callable
-    def getIntersections():
+    def getIntersections():  # type: ignore[misc]
         pass
 
     getIntersections = Callable(getIntersections)
 
     @BooleanClassExtentHelper(OWL_NS.unionOf)
     @Callable
-    def getUnions():
+    def getUnions():  # type: ignore[misc]
         pass
 
     getUnions = Callable(getUnions)

rdflib/graph.py

@@ -1,4 +1,4 @@
-from typing import Optional, Union
+from typing import Optional, Union, Type, cast, overload
 import logging
 from warnings import warn
 import random
@@ -20,7 +20,7 @@
 import shutil
 import tempfile
 
-from io import BytesIO
+from io import BytesIO, BufferedIOBase
 from urllib.parse import urlparse
 
 assert Literal  # avoid warning
@@ -956,8 +956,82 @@ def absolutize(self, uri, defrag=1):
         """Turn uri into an absolute URI if it's not one already"""
         return self.namespace_manager.absolutize(uri, defrag)
 
+    # no destination and non-None positional encoding
+    @overload
     def serialize(
-        self, destination=None, format="turtle", base=None, encoding=None, **args
+        self, destination: None, format: str, base: Optional[str], encoding: str, **args
+    ) -> bytes:
+        ...
+
+    # no destination and non-None keyword encoding
+    @overload
+    def serialize(
+        self,
+        *,
+        destination: None = ...,
+        format: str = ...,
+        base: Optional[str] = ...,
+        encoding: str,
+        **args
+    ) -> bytes:
+        ...
+
+    # no destination and None positional encoding
+    @overload
+    def serialize(
+        self,
+        destination: None,
+        format: str,
+        base: Optional[str],
+        encoding: None,
+        **args
+    ) -> str:
+        ...
+
+    # no destination and None keyword encoding
+    @overload
+    def serialize(
+        self,
+        *,
+        destination: None = ...,
+        format: str = ...,
+        base: Optional[str] = ...,
+        encoding: None = None,
+        **args
+    ) -> str:
+        ...
+
+    # non-none destination
+    @overload
+    def serialize(
+        self,
+        destination: Union[str, BufferedIOBase],
+        format: str = ...,
+        base: Optional[str] = ...,
+        encoding: Optional[str] = ...,
+        **args
+    ) -> None:
+        ...
+
+    # fallback
+    @overload
+    def serialize(
+        self,
+        destination: Union[str, BufferedIOBase, None] = None,
+        format: str = "turtle",
+        base: Optional[str] = None,
+        encoding: Optional[str] = None,
+        **args
+    ) -> Optional[Union[bytes, str]]:
+        ...
+
+    def serialize(
+        self,
+        destination: Union[str, BufferedIOBase, None] = None,
+        format: str = "turtle",
+        base: Optional[str] = None,
+        encoding: Optional[str] = None,
+        **args
     ) -> Optional[Union[bytes, str]]:
         """Serialize the Graph to destination
 
@@ -978,6 +1052,7 @@ def serialize(
             base = self.base
 
         serializer = plugin.get(format, Serializer)(self)
+        stream: BufferedIOBase
         if destination is None:
             stream = BytesIO()
             if encoding is None:
@@ -987,16 +1062,16 @@ def serialize(
                 serializer.serialize(stream, base=base, encoding=encoding, **args)
                 return stream.getvalue()
         if hasattr(destination, "write"):
-            stream = destination
+            stream = cast(BufferedIOBase, destination)
             serializer.serialize(stream, base=base, encoding=encoding, **args)
         else:
-            location = destination
+            location = cast(str, destination)
             scheme, netloc, path, params, _query, fragment = urlparse(location)
             if netloc != "":
                 print(
                     "WARNING: not saving as location" + "is not a local file reference"
                 )
-                return
+                return None
             fd, name = tempfile.mkstemp()
             stream = os.fdopen(fd, "wb")
             serializer.serialize(stream, base=base, encoding=encoding, **args)
@@ -1007,6 +1082,7 @@ def serialize(
             else:
                 shutil.copy(name, dest)
                 os.remove(name)
+        return None
 
     def print(self, format="turtle", encoding="utf-8", out=None):
         print(
@@ -1146,8 +1222,8 @@ def load(self, source, publicID=None, format="xml"):
     def query(
         self,
         query_object,
-        processor: str = "sparql",
-        result: str = "sparql",
+        processor: Union[str, query.Processor] = "sparql",
+        result: Union[str, Type[query.Result]] = "sparql",
         initNs=None,
         initBindings=None,
         use_store_provided: bool = True,
@@ -1183,7 +1259,7 @@ def query(
                 pass  # store has no own implementation
 
         if not isinstance(result, query.Result):
-            result = plugin.get(result, query.Result)
+            result = plugin.get(cast(str, result), query.Result)
         if not isinstance(processor, query.Processor):
             processor = plugin.get(processor, query.Processor)(self)
 

rdflib/parser.py

@@ -39,7 +39,7 @@
 
 
 class Parser(object):
-    __slots__ = set()
+    __slots__ = ()
 
     def __init__(self):
         pass

rdflib/paths.py

@@ -184,6 +184,7 @@
 
 
 from rdflib.term import URIRef, Node
+from typing import Union, Callable
 
 
 # property paths
@@ -194,6 +195,13 @@
 
 
 class Path(object):
+
+    __or__: Callable[["Path", Union["URIRef", "Path"]], "AlternativePath"]
+    __invert__: Callable[["Path"], "InvPath"]
+    __neg__: Callable[["Path"], "NegatedPath"]
+    __truediv__: Callable[["Path", Union["URIRef", "Path"]], "SequencePath"]
+    __mul__: Callable[["Path", str], "MulPath"]
+
     def eval(self, graph, subj=None, obj=None):
         raise NotImplementedError()
 
@@ -502,7 +510,9 @@ def neg_path(p):
     #  as it would introduce circular imports)
 
     URIRef.__or__ = path_alternative
-    URIRef.__mul__ = mul_path
+    # ignore typing here as URIRef inherits from str,
+    # which has an incompatible definition of __mul__.
+    URIRef.__mul__ = mul_path  # type: ignore
     URIRef.__invert__ = inv_path
     URIRef.__neg__ = neg_path
     URIRef.__truediv__ = path_sequence