mypy: Type simple generators as Iterator, not Iterable.

A generator that yields values without receiving or returning them is
an Iterator.  Although every Iterator happens to be iterable, Iterable
is a confusing annotation for generators because a generator is only
iterable once.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

tools/documentation_crawler/documentation_crawler/spiders/common/spiders.py

@@ -1,6 +1,6 @@
 import json
 import re
-from typing import Callable, Iterable, List, Optional, Union
+from typing import Callable, Iterator, List, Optional, Union
 
 import scrapy
 from scrapy.http import Request, Response
@@ -105,8 +105,8 @@ class BaseDocumentationSpider(scrapy.Spider):
 
         return callback
 
-    def _make_requests(self, url: str) -> Iterable[Request]:
-        callback: Callable[[Response], Optional[Iterable[Request]]] = self.parse
+    def _make_requests(self, url: str) -> Iterator[Request]:
+        callback: Callable[[Response], Optional[Iterator[Request]]] = self.parse
         dont_filter = False
         method = 'GET'
         if self._is_external_url(url):
@@ -120,11 +120,11 @@ class BaseDocumentationSpider(scrapy.Spider):
         yield Request(url, method=method, callback=callback, dont_filter=dont_filter,
                       errback=self.error_callback)
 
-    def start_requests(self) -> Iterable[Request]:
+    def start_requests(self) -> Iterator[Request]:
         for url in self.start_urls:
             yield from self._make_requests(url)
 
-    def parse(self, response: Response) -> Iterable[Request]:
+    def parse(self, response: Response) -> Iterator[Request]:
         self.log(response)
 
         if getattr(self, 'validate_html', False):
@@ -142,7 +142,7 @@ class BaseDocumentationSpider(scrapy.Spider):
                                       canonicalize=False).extract_links(response):
             yield from self._make_requests(link.url)
 
-    def retry_request_with_get(self, request: Request) -> Iterable[Request]:
+    def retry_request_with_get(self, request: Request) -> Iterator[Request]:
         request.method = 'GET'
         request.dont_filter = True
         yield request
@@ -150,7 +150,7 @@ class BaseDocumentationSpider(scrapy.Spider):
     def exclude_error(self, url: str) -> bool:
         return url in EXCLUDED_URLS
 
-    def error_callback(self, failure: Failure) -> Optional[Union[Failure, Iterable[Request]]]:
+    def error_callback(self, failure: Failure) -> Optional[Union[Failure, Iterator[Request]]]:
         if failure.check(HttpError):
             response = failure.value.response
             if self.exclude_error(response.url):

zerver/data_import/import_util.py

@@ -2,7 +2,19 @@ import logging
 import os
 import random
 import shutil
-from typing import AbstractSet, Any, Callable, Dict, Iterable, List, Optional, Set, Tuple, TypeVar
+from typing import (
+    AbstractSet,
+    Any,
+    Callable,
+    Dict,
+    Iterable,
+    Iterator,
+    List,
+    Optional,
+    Set,
+    Tuple,
+    TypeVar,
+)
 
 import requests
 import ujson
@@ -576,7 +588,7 @@ def write_avatar_png(avatar_folder: str,
 
 ListJobData = TypeVar('ListJobData')
 def run_parallel_wrapper(f: Callable[[ListJobData], None], full_items: List[ListJobData],
-                         threads: int=6) -> Iterable[Tuple[int, List[ListJobData]]]:
+                         threads: int=6) -> Iterator[Tuple[int, List[ListJobData]]]:
     logging.info("Distributing %s items across %s threads", len(full_items), threads)
 
     def wrapping_function(items: List[ListJobData]) -> int:

zerver/lib/utils.py

@@ -7,7 +7,7 @@ import re
 import string
 from itertools import zip_longest
 from time import sleep
-from typing import Any, Callable, Iterable, List, Optional, Sequence, Set, Tuple, TypeVar
+from typing import Any, Callable, Iterator, List, Optional, Sequence, Set, Tuple, TypeVar
 
 from django.conf import settings
 
@@ -122,7 +122,7 @@ def has_api_key_format(key: str) -> bool:
 def query_chunker(queries: List[Any],
                   id_collector: Optional[Set[int]]=None,
                   chunk_size: int=1000,
-                  db_chunk_size: Optional[int]=None) -> Iterable[Any]:
+                  db_chunk_size: Optional[int]=None) -> Iterator[Any]:
     '''
     This merges one or more Django ascending-id queries into
     a generator that returns chunks of chunk_size row objects
@@ -149,7 +149,7 @@ def query_chunker(queries: List[Any],
     else:
         id_collector = set()
 
-    def chunkify(q: Any, i: int) -> Iterable[Tuple[int, int, Any]]:
+    def chunkify(q: Any, i: int) -> Iterator[Tuple[int, int, Any]]:
         q = q.order_by('id')
         min_id = -1
         while True:

zerver/management/commands/makemessages.py

@@ -34,7 +34,7 @@ import json
 import os
 import re
 from argparse import ArgumentParser
-from typing import Any, Dict, Iterable, List, Mapping
+from typing import Any, Dict, Iterable, Iterator, List, Mapping
 
 from django.core.management.commands import makemessages
 from django.template.base import BLOCK_TAG_END, BLOCK_TAG_START
@@ -205,7 +205,7 @@ class Command(makemessages.Command):
     def get_base_path(self) -> str:
         return self.frontend_output
 
-    def get_output_paths(self) -> Iterable[str]:
+    def get_output_paths(self) -> Iterator[str]:
         base_path = self.get_base_path()
         locales = self.get_locales()
         for path in [os.path.join(base_path, locale) for locale in locales]:

zerver/tests/test_import_export.py

@@ -181,7 +181,7 @@ class QueryUtilTest(ZulipTestCase):
             id_collector=all_msg_ids,
             chunk_size=10,  # use a different size each time
         )
-        first_chunk = next(chunker)  # type: ignore[call-overload]
+        first_chunk = next(chunker)
         self.assertEqual(len(first_chunk), 10)
         self.assertEqual(len(all_msg_ids), 10)
         expected_msg = Message.objects.all()[0:10][5]