Make NameExtractor work correctly when the locations list is empty

Previously, NameExtractor raised a hard to understand error in this
case. This was then improved to a clearer error message. This commit now
prevents the error message completely: if the list of locations passed
to Pipeline is empty, then NameExtractor.extract simply yields no
matches.

This reverts commit 18916c1, reversing
changes made to 38b7526.

CHANGELOG.md

@@ -4,6 +4,16 @@ The format of this file is based on [Keep a Changelog], and this
 project uses [Semantic Versioning].
 
 
+## [Unreleased]
+
+### Fixed
+
+- `NameExtractor` previously raised a hard to understand error message when the
+  location list passed to the `Pipeline` was empty. It now handles this edge
+  case correctly without raising an exception.
+  ([#5], with contributions by [@konstin])
+
+
 ## [0.3.0] (2017-07-07)
 
 ### Added
@@ -88,3 +98,6 @@ First release.
 [0.2.0]: https://github.com/stadt-karlsruhe/geoextract/compare/v0.1.0...v0.2.0
 [0.1.0]: https://github.com/stadt-karlsruhe/geoextract/commits/v0.1.0
 
+[#5]: https://github.com/stadt-karlsruhe/geoextract/pull/5
+
+[@konstin]: https://github.com/konstin

geoextract/__init__.py

@@ -183,10 +183,6 @@ def setup(self, pipeline):  # noqa: D102
         # avoid finding parts of words. That of course assumes that other
         # word delimiters have been converted to spaces during
         # normalization.
-
-        if not pipeline.normalized_names:
-            raise ValueError("You must provide locations for extraction")
-
         self._automaton = ahocorasick.Automaton()
         for name in pipeline.normalized_names:
             name = name.strip()
@@ -195,8 +191,12 @@ def setup(self, pipeline):  # noqa: D102
 
     def extract(self, text):  # noqa: D102
         text = self._pad(text)
-
-        for end_index, name in self._automaton.iter(text):
+        try:
+            it = self._automaton.iter(text)
+        except AttributeError:
+            # Occurs when the list of locations was empty
+            return
+        for end_index, name in it:
             end_index -= 1  # Trailing padding space
             if PY2:
                 # UTF-8 encoded text might require more characters than the

tests/__init__.py

@@ -38,13 +38,6 @@
 
 import requests
 
-DUMMY_LOCATIONS = [
-    {
-        'name': 'FooBar',
-        'type': 'street'
-    }
-]
-
 
 def wait_for_server(url, max_tries=10, delay=1):
     '''

tests/test_app.py

@@ -36,7 +36,8 @@
 import requests
 
 from geoextract import __version__ as geoextract_version, Pipeline
-from . import DUMMY_LOCATIONS, stop_process, wait_for_server
+from . import stop_process, wait_for_server
+
 
 SERVER_URL = 'http://localhost:5000'
 EXTRACT_URL = SERVER_URL + '/api/v1/extract'
@@ -73,7 +74,7 @@ def stop(self):
 
 
 @contextlib.contextmanager
-def app(locations=DUMMY_LOCATIONS, *args, **kwargs):
+def app(locations=(), *args, **kwargs):
     '''
     Context manager that provides a geoextract app.
 

tests/test_geoextract.py

@@ -34,7 +34,7 @@
 import mock
 
 import geoextract
-from . import DUMMY_LOCATIONS, sort_as_json
+from . import sort_as_json
 
 
 class TestNameExtractor(object):
@@ -85,6 +85,14 @@ def test_word_only_matches(self):
         '''
         self._check('xfoo xfooy foox', [])
 
+    def test_no_locations(self):
+        '''
+        Test that the extractor works with an empty list of locations.
+        '''
+        extractor = geoextract.NameExtractor()
+        pipeline = geoextract.Pipeline([], extractors=[extractor])
+        assert pipeline.extract('foobar') == []
+
 
 class TestWindowExtractor(object):
     '''
@@ -864,17 +872,6 @@ def test_app_creation(self):
         '''
         Test creating a web app from a pipeline.
         '''
-        pipeline = geoextract.Pipeline(DUMMY_LOCATIONS)
+        pipeline = geoextract.Pipeline([])
         app = pipeline.create_app()
         assert hasattr(app, 'run')
-
-    def test_empty_locations(self):
-        '''
-        Tests that an empty locations list throws an error.
-        '''
-        try:
-            geoextract.Pipeline([])
-            assert False
-        except ValueError as e:
-            error_message = "You must provide locations for extraction"
-            assert str(e) == str(ValueError(error_message))