Fix: InsertValue will error if input is None

slurry/sections/_producers.py

@@ -119,6 +119,8 @@ class InsertValue(TrioSection):
     """Inserts a single user supplied value into the pipeline on startup and then
     passes through any further received items unmodified.
 
+    If no input is used, the single value will be sent, and InsertValue will close.
+
     :param value: Item to send on startup.
     :type value: Any
     """
@@ -127,5 +129,6 @@ def __init__(self, value: Any) -> None:
 
     async def refine(self, input, output):
         await output(self.value)
-        async for item in input:
-            await output(item)
+        if input:
+            async for item in input:
+                await output(item)

tests/test_producers.py

@@ -2,7 +2,7 @@
 import trio
 
 from slurry import Pipeline
-from slurry.sections import Repeat, Metronome, InsertValue
+from slurry.sections import Repeat, Metronome, InsertValue, _producers
 
 from .fixtures import produce_alphabet
 
@@ -51,19 +51,27 @@ async def test_repeat_input(autojump_clock):
                 break
     assert results == [('a', 1), ('a', 2), ('b', 2.5), ('b', 3.5), ('c', 4)]
 
-async def test_metronome():
+async def test_metronome(autojump_clock, monkeypatch):
+    monkeypatch.setattr(_producers, "time", trio.current_time)
     async with Pipeline.create(
-        produce_alphabet(5, max=3),
+        produce_alphabet(5, max=6, delay=1),
         Metronome(5)
     ) as pipeline, pipeline.tap() as aiter:
         results = []
-        start_time = trio.current_time()
         async for item in aiter:
-            results.append((item, trio.current_time() - start_time))
-            if len(results) == 2:
-                break
-    assert [x[0] for x in results] == ['a', 'b']
-    assert 5 - results[1][1] + results[0][1] < 0.1
+            results.append((item, trio.current_time()))
+    assert results == [(letter, 5.0 * (i + 1)) for i, letter in enumerate("abcde")]
+
+async def test_metronome_no_input(autojump_clock, monkeypatch):
+    monkeypatch.setattr(_producers, "time", trio.current_time)
+    async with Pipeline.create(
+        Metronome(5, "a")
+    ) as pipeline, pipeline.tap() as aiter:
+        results = []
+        for _ in range(5):
+            item = await aiter.__anext__()
+            results.append((item, trio.current_time()))
+    assert results == [("a", 5.0 * (i + 1)) for i in range(5)]
 
 async def test_insert_value(autojump_clock):
     async with Pipeline.create(
@@ -73,3 +81,10 @@ async def test_insert_value(autojump_clock):
         start_time = trio.current_time()
         results = [(v, trio.current_time() - start_time) async for v in aiter]
         assert results == [('n', 0), ('a', 1), ('b', 2), ('c', 3)]
+
+async def test_insert_value_no_input(autojump_clock):
+    async with Pipeline.create(
+        InsertValue('n')
+    ) as pipeline, pipeline.tap() as aiter:
+        results = [v async for v in aiter]
+        assert results == ['n']