Add stat support (#159)

docs/index.rst

@@ -44,6 +44,7 @@ To get started, see :ref:`intro-install` and :ref:`intro-tutorial`.
    :maxdepth: 1
 
    rules-from-web-poet
+   stats
    providers
    testing
 

docs/stats.rst

@@ -0,0 +1,8 @@
+.. _stats:
+
+=====
+Stats
+=====
+
+scrapy-poet tracks :external+web-poet:ref:`web-poet stats <stats>` as part of
+:ref:`Scrapy stats <topics-stats>`, prefixed with ``poet/stats/``.

scrapy_poet/page_input_providers.py

@@ -27,7 +27,9 @@
     PageParams,
     RequestUrl,
     ResponseUrl,
+    Stats,
 )
+from web_poet.page_inputs.stats import StatCollector, StatNum
 from web_poet.pages import is_injectable
 
 from scrapy_poet.downloader import create_scrapy_downloader
@@ -333,3 +335,31 @@ async def __call__(
 
             results.append(item)
         return results
+
+
+class ScrapyPoetStatCollector(StatCollector):
+    def __init__(self, stats):
+        self._stats = stats
+        self._prefix = "poet/stats/"
+
+    def set(self, key: str, value: Any) -> None:  # noqa: D102
+        self._stats.set_value(f"{self._prefix}{key}", value)
+
+    def inc(self, key: str, value: StatNum = 1) -> None:  # noqa: D102
+        self._stats.inc_value(f"{self._prefix}{key}", value)
+
+
+class StatsProvider(PageObjectInputProvider):
+    """This class provides :class:`web_poet.Stats
+    <web_poet.page_inputs.client.Stats>` instances.
+    """
+
+    provided_classes = {Stats}
+
+    def __call__(self, to_provide: Set[Callable], crawler: Crawler):
+        """Creates an :class:`web_poet.Stats
+        <web_poet.page_inputs.client.Stats>` instance using Scrapy's
+        stat collector.
+        """
+
+        return [Stats(stat_collector=ScrapyPoetStatCollector(crawler.stats))]

setup.py

@@ -29,7 +29,7 @@
         "time_machine",
         "twisted >= 18.9.0",
         "url-matcher >= 0.2.0",
-        "web-poet >= 0.12.0",
+        "web-poet >= 0.15",
     ],
     classifiers=[
         "Development Status :: 3 - Alpha",

tests/test_providers.py

@@ -18,6 +18,7 @@
     ItemProvider,
     PageObjectInputProvider,
     PageParamsProvider,
+    StatsProvider,
 )
 from scrapy_poet.utils.mockserver import get_ephemeral_port
 from scrapy_poet.utils.testing import (
@@ -253,3 +254,25 @@ def inside():
     # garbage collected.
     inside()
     assert len(provider._cached_instances) == 0
+
+
+def test_stats_provider(settings):
+    crawler = get_crawler(Spider, settings)
+    injector = Injector(crawler)
+    provider = StatsProvider(injector)
+
+    results = provider(set(), crawler)
+
+    stats = results[0]
+    assert stats._stats._stats == crawler.stats
+
+    stats.set("a", "1")
+    stats.set("b", 2)
+    stats.inc("b")
+    stats.inc("b", 5)
+    stats.inc("c")
+
+    expected = {"a": "1", "b": 8, "c": 1}
+    expected = {f"poet/stats/{k}": v for k, v in expected.items()}
+    actual = {k: v for k, v in crawler.stats._stats.items() if k in expected}
+    assert actual == expected