private static MemberBinding GetBinding(GraphQLSchema <TContext> schema, ExecSelection <Info> map, Type toType, Expression baseBindingExpr, ExpressionOptions options)
{
var field = map.SchemaField.Field();
var needsTypeCheck = baseBindingExpr.Type != field.DefiningType.CLRType;
var toMember = toType.GetProperty(map.SchemaField.FieldName);
// expr is form of: (context, entity) => entity.Field
var expr = field.GetExpression(map.Arguments.Values());
// The field might be defined on sub-types of the specified type, so add a type cast if necessary.
// If appropriate, `entity.Field` becomes `(entity as TFieldDefiningType).Field`
var typeCastedBaseExpression = needsTypeCheck ? Expression.TypeAs(baseBindingExpr, field.DefiningType.CLRType) : baseBindingExpr;
// Replace (entity) with baseBindingExpr, note expression is no longer a LambdaExpression
// `(context, entity) => entity.Field` becomes `someOtherEntity.Entity.Field` where baseBindingExpr is `someOtherEntity.Entity`
var replacedBase = ParameterReplacer.Replace(expr.Body, expr.Parameters[1], typeCastedBaseExpression);
// If the entity has to be casted, add a type check:
// `(someOtherEntity.Entity as TFieldDefininingType).Field` becomes `(someOtherEntity.Entity is TFieldDefininingType) ? (someOtherEntity.Entity as TFieldDefininingType).Field : null`
if (needsTypeCheck && options.TypeCheckInheritance)
{
// The expression type has to be nullable
if (replacedBase.Type.IsValueType)
{
replacedBase = Expression.Convert(replacedBase, typeof(Nullable <>).MakeGenericType(replacedBase.Type));
}
var typeCheck = Expression.TypeIs(baseBindingExpr, field.DefiningType.CLRType);
var nullResult = Expression.Constant(null, replacedBase.Type);
replacedBase = Expression.Condition(typeCheck, replacedBase, nullResult);
}
// This just makes sure that the (context) parameter is the same as the one used by the whole query
var replacedContext = ParameterReplacer.Replace(replacedBase, expr.Parameters[0], GraphQLSchema <TContext> .DbParam);
// If there aren't any children, then we can assume that this is a scalar entity and we don't have to map child fields
if (!map.Selections.Any())
{
if (options.CastAssignment && expr.Body.Type != toMember.PropertyType)
{
replacedContext = Expression.Convert(replacedContext, toMember.PropertyType);
}
return(Expression.Bind(toMember, replacedContext));
}
// If binding a single entity, just use the already built selector expression (replaced context)
// Otherwise, if binding to a list, introduce a new parameter that will be used in a call to .Select
var listParameter = Expression.Parameter
(field.Type.CLRType, field.Type.CLRType.Name.Substring(0, 1).ToLower()); // TODO: Name conflicts in expressions?
var bindChildrenTo = map.SchemaField.Field().IsList ? listParameter : replacedContext;
// Now that we have our new binding parameter, build the tree for the rest of the children
var memberInit = GetMemberInit(schema, field.Type.QueryType, map.Selections.Values(), bindChildrenTo, options);
// For single entities, we're done and we can just bind to the memberInit expression
if (!field.IsList)
{
return(Expression.Bind(toMember, memberInit));
}
// However for lists, we need to check for null and call .Select() and .ToList() first
var selectLambda = Expression.Lambda(memberInit, listParameter);
var call = Expression.Call(typeof(Enumerable), "Select", new[] { field.Type.CLRType, field.Type.QueryType }, replacedContext, selectLambda);
var toList = Expression.Call(typeof(Enumerable), "ToList", new[] { field.Type.QueryType }, call);
return(Expression.Bind(toMember, options.NullCheckLists ? (Expression)NullPropagate(replacedContext, toList) : toList));
}
private static LambdaExpression GetSelector(GraphQLSchema <TContext> schema, GraphQLType gqlType, IEnumerable <ExecSelection <Info> > selections, ExpressionOptions options)
{
var parameter = Expression.Parameter(gqlType.CLRType, "p");
var init = GetMemberInit(schema, gqlType.QueryType, selections, parameter, options);
return(Expression.Lambda(init, parameter));
}
private static ConditionalExpression GetMemberInit(GraphQLSchema <TContext> schema, Type queryType, IEnumerable <ExecSelection <Info> > selectionsEnumerable, Expression baseBindingExpr, ExpressionOptions options)
{
// Avoid possible multiple enumeration of selections-enumerable
var selections = selectionsEnumerable as IList <ExecSelection <Info> > ?? selectionsEnumerable.ToList();
// The '__typename'-field selection has to be added for queries with type conditions
var typeConditionButNoTypeNameSelection = selections.Any() &&
selections.Any(s => s.TypeCondition != null);
// Any '__typename' selection have to be replaced by the '__typename' selection of the target type' '__typename'-field.
var typeNameConditionHasToBeReplaced = selections.Any(s => s.Name == TypenameFieldSelector);
// Remove all '__typename'-selections as well as duplicates in the selections caused by fragments type condition selections.
selections = selections
.Where(s => s.Name != TypenameFieldSelector)
.GroupBy(s => s.Name)
.Select(g => g.First())
.ToList();
var bindings = selections
.Where(m => !m.SchemaField.Field().IsPost)
.Select(map => GetBinding(schema, map, queryType, baseBindingExpr, options))
.ToList();
// Add selection for '__typename'-field of the proper type
if (typeConditionButNoTypeNameSelection || typeNameConditionHasToBeReplaced)
{
// Find the base types' `__typename` field
var graphQlType = schema.GetGQLType(baseBindingExpr.Type);
while (graphQlType?.BaseType != null)
{
graphQlType = graphQlType.BaseType;
}
var typeNameField = graphQlType?.OwnFields.Find(f => f.Name == TypenameFieldSelector);
if (typeNameField != null && !typeNameField.IsPost)
{
var typeNameExecSelection = new ExecSelection <Info>(
new SchemaField(
schema.Adapter.QueryTypes[graphQlType?.Name],
typeNameField,
schema.Adapter),
new FSharpOption <string>(typeNameField?.Name),
null,
new WithSource <ExecArgument <Info> >[] { },
new WithSource <ExecDirective <Info> >[] { },
new WithSource <ExecSelection <Info> >[] { }
);
bindings = bindings.Concat(new[] { GetBinding(schema, typeNameExecSelection, queryType, baseBindingExpr, options) }).ToList();
}
}
var memberInit = Expression.MemberInit(Expression.New(queryType), bindings);
return(NullPropagate(baseBindingExpr, memberInit));
}
private static ConditionalExpression GetMemberInit(GraphQLSchema <TContext> schema, GraphQLType graphQlType, IEnumerable <ExecSelection <Info> > selectionsEnumerable, Expression parameterExpression, ExpressionOptions options)
{
var queryType = graphQlType.QueryType;
// Avoid possible multiple enumeration of selections-enumerable
var selections = selectionsEnumerable as IList <ExecSelection <Info> > ?? selectionsEnumerable.ToList();
// The '__typename'-field selection has to be added for queries with type conditions
var typeConditionButNoTypeNameSelection = selections.Any() &&
selections.Any(s => s.TypeCondition != null);
// Any '__typename' selection have to be replaced by the '__typename' selection of the target type' '__typename'-field.
var typeNameConditionHasToBeReplaced = selections.Any(s => s.Name == "__typename");
var bindingsWithPossibleDuplicates =
selections.Where(s => !s.SchemaField.Info.Field.IsPost)
.Where(s => s.Name != "__typename")
.Select(s => GetBinding(schema, s, graphQlType, parameterExpression, options))
.ToList();
var uniqueBindingMemberNames = bindingsWithPossibleDuplicates.Select(b => b.Member.Name).Distinct();
var bindings =
uniqueBindingMemberNames.Select(name => bindingsWithPossibleDuplicates.First(b => b.Member.Name == name));
// Add selection for '__typename'-field of the proper type
if (typeConditionButNoTypeNameSelection || typeNameConditionHasToBeReplaced)
{
// Find the base types' `__typename` field
var typeNameField = graphQlType?.Fields.Find(f => f.Name == "__typename");
if (typeNameField != null && !typeNameField.IsPost)
{
var typeNameExecSelection = new ExecSelection <Info>(
new SchemaField(
schema.Adapter.QueryTypes[graphQlType?.Name],
typeNameField,
schema.Adapter),
new FSharpOption <string>(typeNameField?.Name),
null,
new WithSource <ExecArgument <Info> >[] {},
new WithSource <ExecDirective <Info> >[] {},
new WithSource <ExecSelection <Info> >[] {}
);
bindings =
bindings
.Where(b => b.Member.Name != "__typename")
.Concat(new[]
{ GetBinding(schema, typeNameExecSelection, graphQlType, parameterExpression, options) })
.ToList();
}
}
var memberInit = Expression.MemberInit(Expression.New(queryType), bindings);
return(NullPropagate(parameterExpression, memberInit));
}