Add cc.expect.range (#790)

src/main/resources/data/computercraft/lua/rom/modules/main/cc/expect.lua

@@ -88,7 +88,34 @@ local function field(tbl, index, ...)
     end
 end
 
+local function is_nan(num)
+  return num ~= num
+end
+
+--- Expect a number to be within a specific range.
+--
+-- @tparam number num, The value to check.
+-- @tparam number min The minimum value, if nil then `-math.huge` is used.
+-- @tparam number max The maximum value, if nil then `math.huge` is used.
+-- @return The given `value`.
+-- @throws If the value is outside of the allowed range.
+local function range(num, min, max)
+  expect(1, num, "number")
+  min = expect(2, min, "number", "nil") or -math.huge
+  max = expect(3, max, "number", "nil") or math.huge
+  if min > max then
+      error("min must be less than or equal to max)", 2)
+  end
+
+  if is_nan(num) or num < min or num > max then
+      error(("number outside of range (expected %s to be within %s and %s)"):format(num, min, max), 3)
+  end
+
+  return num
+end
+
 return {
     expect = expect,
     field = field,
+    range = range,
 }

src/test/resources/test-rom/spec/modules/cc/expect_spec.lua

@@ -50,4 +50,25 @@ describe("cc.expect", function()
                 :eq("bad field 'l' (expected string, table or number, got boolean)")
         end)
     end)
+
+    describe("range", function()
+        it("works fith full args", function()
+            expect(e.range(1, 1, 1)):eq(1)
+            expect(e.range(2, 1, 3)):eq(2)
+
+            expect.error(e.range, 2, 0, 1):eq("number outside of range (expected 2 to be within 0 and 1)")
+            expect.error(e.range, 0, 1, 2):eq("number outside of range (expected 0 to be within 1 and 2)")
+            local NaN = 0 / 0
+            expect.error(e.range, NaN, 1, 2):eq(("number outside of range (expected %s to be within 1 and 2)"):format(tostring(NaN)))
+        end)
+
+        it("fills in min and max if they are nil", function()
+            expect(e.range(1, 1)):eq(1)
+            expect(e.range(2, nil, 3)):eq(2)
+            expect(e.range(2)):eq(2)
+
+            expect.error(e.range, 2, nil, 1):eq("number outside of range (expected 2 to be within -inf and 1)")
+            expect.error(e.range, 0, 1):eq("number outside of range (expected 0 to be within 1 and inf)")
+        end)
+    end)
 end)