// create a delegate that will format the given value (pulled from a getter or a field) into
// a buffer, subject to shouldSerialize being null or returning true
// and return true if it was able to do so
internal static ColumnWriterDelegate Create(TypeInfo type, Options options, Formatter formatter, NonNull<ShouldSerialize> shouldSerialize, Getter getter, bool emitDefaultValue)
{
var p1 = Expressions.Parameter_Object;
var p2 = Expressions.Parameter_WriteContext_ByRef;
var p3 = Expressions.Parameter_IBufferWriterOfChar;
var statements = new List<Expression>();
var p1AsType = Expression.Convert(p1, type);
var l1 = Expression.Variable(type, "l1");
var assignToL1 = Expression.Assign(l1, p1AsType);
statements.Add(assignToL1);
var end = Expression.Label(Types.Bool, "end");
var returnTrue = Expression.Label("return-true");
if (shouldSerialize.HasValue)
{
var ss = shouldSerialize.Value;
if (ss.TakesNullability == NullHandling.ForbidNull && ss.Takes.Value.AllowsNullLikeValue())
{
var takes = ss.Takes.Value;
var checkExp = Utils.MakeNullHandlingCheckExpression(takes, l1, $"{ss} does not accept null rows, but was given one at runtime");
statements.Add(checkExp);
}
var callShouldSerialize = ss.MakeExpression(l1, p2);
var shouldntSerialize = Expression.Not(callShouldSerialize);
var jumpToEnd = Expression.Goto(returnTrue);
var jumpToEndIfShouldntSerialize = Expression.IfThen(shouldntSerialize, jumpToEnd);
statements.Add(jumpToEndIfShouldntSerialize);
}
var columnType = getter.Returns;
var l2 = Expression.Variable(columnType, "l2");
var getExp = getter.MakeExpression(l1, p2);
var assignToL2 = Expression.Assign(l2, getExp);
statements.Add(assignToL2);
if (getter.ReturnsNullability == NullHandling.ForbidNull && columnType.AllowsNullLikeValue())
{
// do we need to check that a null didn't happen at runtime?
var checkExp = Utils.MakeNullHandlingCheckExpression(getter.Returns, l2, $"{getter} was forbidden from return null values, but did return one at runtime");
statements.Add(checkExp);
}
if (!emitDefaultValue)
{
ConstantExpression defValue;
if (columnType.IsValueType)
{
defValue = Expression.Constant(Activator.CreateInstance(columnType));
}
else
{
defValue = Expression.Constant(null, columnType);
}
Expression isDefault;
// intentionally letting GetMethod return null here
if (!columnType.IsValueType || columnType.IsEnum || columnType.IsPrimitive || columnType.GetMethod("op_Equality") != null)
{
isDefault = Expression.Equal(l2, defValue);
}
else
{
var equatableI = Types.IEquatable.MakeGenericType(columnType).GetTypeInfo();
if (columnType.GetInterfaces().Any(i => i == equatableI))
{
var equals = equatableI.GetMethodNonNull(nameof(IEquatable<object>.Equals));
var map = columnType.GetInterfaceMap(equatableI);
MethodInfo? equalsTyped = null;
for (var j = 0; j < map.InterfaceMethods.Length; j++)
{
if (map.InterfaceMethods[j] == equals)
{
equalsTyped = map.TargetMethods[j];
isDefault = Expression.Call(l2, equalsTyped, defValue);
goto done;
}
}
Throw.ImpossibleException($"Could not find typed {nameof(IEquatable<object>.Equals)} method, which shouldn't be possible", options);
return default;
}
else
{
var eqsUntyped = columnType.GetMethodNonNull(nameof(object.Equals));
var defAsObject = Expression.Convert(defValue, Types.Object);
isDefault = Expression.Call(l2, eqsUntyped, defAsObject);
}
}
done:
var ifIsDefaultReturnTrue = Expression.IfThen(isDefault, Expression.Goto(returnTrue));
statements.Add(ifIsDefaultReturnTrue);
}
if (formatter.TakesNullability == NullHandling.ForbidNull && formatter.Takes.AllowsNullLikeValue())
{
// make sure formatter invariant hasn't been violated
var checkExp = Utils.MakeNullHandlingCheckExpression(formatter.Takes, l2, $"{formatter} does not take null values, but received one at runtime");
statements.Add(checkExp);
}
var callFormatter = formatter.MakeExpression(l2, p2, p3);
statements.Add(Expression.Goto(end, callFormatter));
statements.Add(Expression.Label(returnTrue));
statements.Add(Expression.Goto(end, Expressions.Constant_True));
statements.Add(Expression.Label(end, Expressions.Constant_False));
var block = Expression.Block(new[] { l1, l2 }, statements);
var del = Expression.Lambda<ColumnWriterDelegate>(block, p1, p2, p3);
var compiled = del.Compile();
return compiled;
}