[wpiunits] Make Velocity.mult(Time) return Measure<D> (#7162)

Update code generator to allow arbitrary implementations of multiplication methods.

wpiunits/generate_units.py

@@ -258,7 +258,18 @@ UNIT_CONFIGURATIONS = {
     "Velocity": {
         "base_unit": "unit()",
         "generics": {"D": {"extends": "Unit"}},
-        "multiply": {},
+        "multiply": {
+            "Time": {
+                "implementation": inspect.cleandoc(
+                    """
+                  @Override
+                  default Measure<D> times(Time multiplier) {
+                    return (Measure<D>) unit().numerator().ofBaseUnits(baseUnitMagnitude() * multiplier.baseUnitMagnitude());
+                  }
+                """
+                )
+            }
+        },
         "divide": {},
     },
     "Voltage": {"base_unit": "Volts", "multiply": {"Current": "Power"}, "divide": {}},
@@ -310,6 +321,15 @@ def mtou(measure_name):
         return re.sub(regex, "\\1Unit\\2", measure_name)
 
 
+def indent(multiline_string, indentation):
+    """
+    Indents a multiline string by `indentation` number of spaces
+    """
+    return "\n".join(
+        list(map(lambda line: " " * indentation + line, multiline_string.split("\n")))
+    )
+
+
 def main():
 
     dirname, _ = os.path.split(os.path.abspath(__file__))
@@ -331,6 +351,7 @@ def main():
         "generics_list": generics_list,
         "generics_usage": generics_usage,
         "mtou": mtou,
+        "indent": indent,
     }
 
     for unit_name in UNIT_CONFIGURATIONS:

wpiunits/src/generate/main/java/Measure-interface.java.jinja

@@ -80,10 +80,14 @@ public interface {{ helpers['type_decl'](name) }} extends Measure<{{ helpers['mt
   }
 {% else %}
 {% if unit in config[name]['multiply'] %}
+{%- if 'implementation' in config[name]['multiply'][unit] -%}
+{{ helpers['indent'](config[name]['multiply'][unit]['implementation'], 2) }}
+{%- else %}
   @Override
   default {{ config[name]['multiply'][unit] }} times({{ unit }} multiplier) {
     return {{ config[config[name]['multiply'][unit]]['base_unit'] }}.of(baseUnitMagnitude() * multiplier.baseUnitMagnitude());
   }
+{%- endif %}
 {% else %}
   @Override
   default Mult<{{ helpers['mtou'](name) }}, {{ helpers['mtou'](unit) }}> times({{ unit }} multiplier) {

wpiunits/src/generated/main/java/edu/wpi/first/units/measure/Velocity.java

@@ -287,10 +287,9 @@ public interface Velocity<D extends Unit> extends Measure<VelocityUnit<D>> {
     return (Per<VelocityUnit<D>, TemperatureUnit>) Measure.super.divide(divisor);
   }
 
-
   @Override
-  default Mult<VelocityUnit<D>, TimeUnit> times(Time multiplier) {
-    return (Mult<VelocityUnit<D>, TimeUnit>) Measure.super.times(multiplier);
+  default Measure<D> times(Time multiplier) {
+    return (Measure<D>) unit().numerator().ofBaseUnits(baseUnitMagnitude() * multiplier.baseUnitMagnitude());
   }
 
   @Override

wpiunits/src/test/java/edu/wpi/first/units/measure/VelocityTest.java

@@ -0,0 +1,27 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.units.measure;
+
+import static edu.wpi.first.units.Units.Milliseconds;
+import static edu.wpi.first.units.Units.Seconds;
+import static edu.wpi.first.units.Units.Volts;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+
+import edu.wpi.first.units.Measure;
+import edu.wpi.first.units.VelocityUnit;
+import edu.wpi.first.units.VoltageUnit;
+import org.junit.jupiter.api.Test;
+
+class VelocityTest {
+  @Test
+  void velocityTimesTimeReturnsDivisor() {
+    var velocity = VelocityUnit.combine(Volts, Seconds).of(123);
+    var time = Milliseconds.of(100);
+    Measure<VoltageUnit> result = velocity.times(time);
+    // Compile-time test - would fail to compile if the return type was Mult or Measure<?>
+
+    assertInstanceOf(Voltage.class, result);
+  }
+}