metric: Fix precision format (#159)

Author: hugovk

src/humanize/number.py

@@ -562,7 +562,7 @@ def metric(value: float, unit: str = "", precision: int = 3) -> str:
         ordinal_ = "mμnpfazyrq"[(-exponent - 1) // 3]
     else:
         ordinal_ = ""
-    value_ = format(value, ".%if" % (precision - (exponent % 3) - 1))
+    value_ = format(value, ".%if" % max(0, precision - (exponent % 3) - 1))
     if not (unit or ordinal_) or unit in ("°", "′", "″"):
         space = ""
     else:

tests/test_number.py

@@ -269,6 +269,27 @@ def test_clamp(test_args: list[typing.Any], expected: str) -> None:
         ([0.1, "°"], "100m°"),
         ([100], "100"),
         ([0.1], "100 m"),
+        ([1.5123, "", 0], "2"),
+        ([10.5123, "", 0], "11"),
+        ([10.5123, "", 1], "11"),
+        ([10.5123, "", 2], "11"),
+        ([10.5123, "", 3], "10.5"),
+        ([1, "", 0], "1"),
+        ([10, "", 0], "10"),
+        ([100, "", 0], "100"),
+        ([1000, "", 0], "1 k"),
+        ([1, "", 1], "1"),
+        ([10, "", 1], "10"),
+        ([100, "", 1], "100"),
+        ([1000, "", 1], "1 k"),
+        ([1, "", 2], "1.0"),
+        ([10, "", 2], "10"),
+        ([100, "", 2], "100"),
+        ([1000, "", 2], "1.0 k"),
+        ([1, "", 3], "1.00"),
+        ([10, "", 3], "10.0"),
+        ([100, "", 3], "100"),
+        ([1000, "", 3], "1.00 k"),
         ([math.nan], "NaN"),
         ([math.nan, "m"], "NaN"),
         ([math.inf], "+Inf"),