Fix dehumanize not recognizing singular nouns like '1 day ago'

arrow/locales.py

@@ -307,25 +307,31 @@ class EnglishLocale(Locale):
     timeframes = {
         "now": "just now",
         "second": "a second",
-        "seconds": "{0} seconds",
+        "seconds": {"singular": "{0} second", "plural": "{0} seconds"},
         "minute": "a minute",
-        "minutes": "{0} minutes",
+        "minutes": {"singular": "{0} minute", "plural": "{0} minutes"},
         "hour": "an hour",
-        "hours": "{0} hours",
+        "hours": {"singular": "{0} hour", "plural": "{0} hours"},
         "day": "a day",
-        "days": "{0} days",
+        "days": {"singular": "{0} day", "plural": "{0} days"},
         "week": "a week",
-        "weeks": "{0} weeks",
+        "weeks": {"singular": "{0} week", "plural": "{0} weeks"},
         "month": "a month",
-        "months": "{0} months",
+        "months": {"singular": "{0} month", "plural": "{0} months"},
         "quarter": "a quarter",
-        "quarters": "{0} quarters",
+        "quarters": {"singular": "{0} quarter", "plural": "{0} quarters"},
         "year": "a year",
-        "years": "{0} years",
+        "years": {"singular": "{0} year", "plural": "{0} years"},
     }
 
     meridians = {"am": "am", "pm": "pm", "AM": "AM", "PM": "PM"}
 
+    def _format_timeframe(self, timeframe: TimeFrameLiteral, delta: int) -> str:
+        form = self.timeframes[timeframe]
+        if isinstance(form, Mapping):
+            form = form["singular"] if abs(delta) == 1 else form["plural"]
+        return form.format(trunc(abs(delta)))
+
     month_names = [
         "",
         "January",

tests/test_arrow.py

@@ -2987,6 +2987,34 @@ def test_czech_slovak(self):
                 assert arw.dehumanize(past_string, locale=lang) == past
                 assert arw.dehumanize(future_string, locale=lang) == future
 
+    def test_singular_nouns_english(self):
+        """Test that dehumanize recognizes '1 day ago', '1 hour ago', etc.
+
+        Regression test for https://github.com/arrow-py/arrow/issues/1150
+        """
+        arw = arrow.Arrow(2000, 6, 18, 5, 55, 0)
+
+        # All singular units should work with numeric "1"
+        assert arw.dehumanize("1 second ago") == arw.shift(seconds=-1)
+        assert arw.dehumanize("1 minute ago") == arw.shift(minutes=-1)
+        assert arw.dehumanize("1 hour ago") == arw.shift(hours=-1)
+        assert arw.dehumanize("1 day ago") == arw.shift(days=-1)
+        assert arw.dehumanize("1 week ago") == arw.shift(weeks=-1)
+        assert arw.dehumanize("1 month ago") == arw.shift(months=-1)
+        assert arw.dehumanize("1 year ago") == arw.shift(years=-1)
+
+        # Future tense
+        assert arw.dehumanize("in 1 day") == arw.shift(days=1)
+        assert arw.dehumanize("in 1 hour") == arw.shift(hours=1)
+
+        # "a/an" forms should still work
+        assert arw.dehumanize("a day ago") == arw.shift(days=-1)
+        assert arw.dehumanize("an hour ago") == arw.shift(hours=-1)
+
+        # Plural forms should still work
+        assert arw.dehumanize("2 days ago") == arw.shift(days=-2)
+        assert arw.dehumanize("3 hours ago") == arw.shift(hours=-3)
+
 
 class TestArrowIsBetween:
     def test_start_before_end(self):