Round whole numbers and numeric strings in ROUND

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## v3.0.0-rc.5
+
+### Fixed
+
+- `ROUND` now rounds whole numbers and numeric strings. It used to accept only
+  floats, so `ROUND(5)`, `ROUND(2 * 3)` and a whole-number variable all raised a
+  `FunctionClauseError`. A value that is not a number now surfaces as the
+  standard "expression is not a number" `Expression.Error`, as `FIXED` already
+  does.
+
 ## v3.0.0-rc.4
 
 ### Fixed

README.md

@@ -139,7 +139,7 @@ by adding `expression` to your list of dependencies in `mix.exs`:
 ```elixir
 def deps do
   [
-    {:expression, "~> 3.0.0-rc.4"}
+    {:expression, "~> 3.0.0-rc.5"}
   ]
 end
 ```

lib/expression/callbacks/standard.ex

@@ -351,7 +351,8 @@ defmodule Expression.Callbacks.Standard do
     [value] = eval_args!([value], ctx)
 
     value
-    |> Decimal.from_float()
+    |> coerce_to_number!()
+    |> number_to_decimal()
     |> Decimal.round(0)
     |> Decimal.to_string(:normal)
   end
@@ -361,11 +362,15 @@ defmodule Expression.Callbacks.Standard do
     [value, places] = eval_args!([value, places], ctx)
 
     value
-    |> Decimal.from_float()
+    |> coerce_to_number!()
+    |> number_to_decimal()
     |> Decimal.round(places)
     |> Decimal.to_string(:normal)
   end
 
+  defp number_to_decimal(number) when is_float(number), do: Decimal.from_float(number)
+  defp number_to_decimal(number) when is_integer(number), do: Decimal.new(number)
+
   @doc """
   MID extracts part of a string, starting at a specified position and for a specified length.
 

mix.exs

@@ -1,7 +1,7 @@
 defmodule Expression.MixProject do
   use Mix.Project
 
-  @version "3.0.0-rc.4"
+  @version "3.0.0-rc.5"
 
   def project do
     [

test/expression_test.exs

@@ -760,6 +760,35 @@ defmodule ExpressionTest do
               %Expression.Error{message: "expression is not a number: `\"not a number\"`"}} =
                Expression.evaluate_block("fixed(value, 2, true)", %{"value" => "not a number"})
     end
+
+    test "round/1 rounds a whole number to itself" do
+      assert {:ok, "4"} == Expression.evaluate_block("round(value)", %{"value" => 4})
+    end
+
+    test "round/2 rounds a whole number to the given places" do
+      assert {:ok, "4.00"} == Expression.evaluate_block("round(value, 2)", %{"value" => 4})
+    end
+
+    test "round/1 with a numeric string still rounds the number" do
+      assert {:ok, "4"} == Expression.evaluate_block("round(value)", %{"value" => "3.7"})
+    end
+
+    test "round/1 with a non-numeric value returns an error tuple instead of crashing" do
+      assert {:error,
+              %Expression.Error{message: "expression is not a number: `\"not a number\"`"}} =
+               Expression.evaluate_block("round(value)", %{"value" => "not a number"})
+    end
+
+    test "round/1 with a nil value returns an error tuple instead of crashing" do
+      assert {:error, %Expression.Error{message: "expression is not a number: `nil`"}} =
+               Expression.evaluate_block("round(value)", %{"value" => nil})
+    end
+
+    test "round/2 with a non-numeric value returns an error tuple instead of crashing" do
+      assert {:error,
+              %Expression.Error{message: "expression is not a number: `\"not a number\"`"}} =
+               Expression.evaluate_block("round(value, 2)", %{"value" => "not a number"})
+    end
   end
 
   test "escaping" do