public override MSAst.Expression Reduce() {
if (_names == _star) {
// from a[.b] import *
return GlobalParent.AddDebugInfo(
Ast.Call(
AstMethods.ImportStar,
Parent.LocalContext,
AstUtils.Constant(_root.MakeString()),
AstUtils.Constant(GetLevel())
),
Span
);
} else {
// from a[.b] import x [as xx], [ y [ as yy] ] [ , ... ]
ReadOnlyCollectionBuilder<MSAst.Expression> statements = new ReadOnlyCollectionBuilder<MSAst.Expression>();
MSAst.ParameterExpression module = Ast.Variable(typeof(object), "module");
// Create initializer of the array of names being passed to ImportWithNames
MSAst.Expression[] names = new MSAst.Expression[_names.Length];
for (int i = 0; i < names.Length; i++) {
names[i] = AstUtils.Constant(_names[i]);
}
// module = PythonOps.ImportWithNames(<context>, _root, make_array(_names))
statements.Add(
GlobalParent.AddDebugInfoAndVoid(
AssignValue(
module,
LightExceptions.CheckAndThrow(
Expression.Call(
AstMethods.ImportWithNames,
Parent.LocalContext,
AstUtils.Constant(_root.MakeString()),
Ast.NewArrayInit(typeof(string), names),
AstUtils.Constant(GetLevel())
)
)
),
_root.Span
)
);
// now load all the names being imported and assign the variables
for (int i = 0; i < names.Length; i++) {
statements.Add(
GlobalParent.AddDebugInfoAndVoid(
AssignValue(
Parent.GetVariableExpression(_variables[i]),
Ast.Call(
AstMethods.ImportFrom,
Parent.LocalContext,
module,
names[i]
)
),
Span
)
);
}
statements.Add(AstUtils.Empty());
return GlobalParent.AddDebugInfo(Ast.Block(new[] { module }, statements.ToArray()), Span);
}
}
internal override MSAst.Expression TransformSet(SourceSpan span, MSAst.Expression right, PythonOperationKind op)
{
// if we just have a simple named multi-assignment (e.g. a, b = 1,2)
// then go ahead and step over the entire statement at once. If we have a
// more complex statement (e.g. a.b, c.d = 1, 2) then we'll step over the
// sets individually as they could be property sets the user wants to step
// into. TODO: Enable stepping of the right hand side?
bool emitIndividualSets = false;
foreach (Expression e in _items)
{
if (IsComplexAssignment(e))
{
emitIndividualSets = true;
break;
}
}
SourceSpan rightSpan = SourceSpan.None;
SourceSpan leftSpan =
(Span.Start.IsValid && span.IsValid) ?
new SourceSpan(Span.Start, span.End) :
SourceSpan.None;
SourceSpan totalSpan = SourceSpan.None;
if (emitIndividualSets)
{
rightSpan = span;
leftSpan = SourceSpan.None;
totalSpan = (Span.Start.IsValid && span.IsValid) ?
new SourceSpan(Span.Start, span.End) :
SourceSpan.None;
}
// 1. Evaluate the expression and assign the value to the temp.
MSAst.ParameterExpression right_temp = Expression.Variable(typeof(object), "unpacking");
// 2. Add the assignment "right_temp = right" into the suite/block
MSAst.Expression assignStmt1 = MakeAssignment(right_temp, right);
int expected = _items.Length;
int argcntafter = -1;
for (var i = 0; i < _items.Length; i++)
{
var item = _items[i];
if (item is StarredExpression)
{
expected = i;
argcntafter = _items.Length - i - 1;
break;
}
}
// 3. Call GetEnumeratorValues on the right side (stored in temp)
MSAst.Expression enumeratorValues = Expression.Convert(LightExceptions.CheckAndThrow(
Expression.Call(
// method
argcntafter != -1 ?
AstMethods.UnpackIterable :
emitIndividualSets ?
AstMethods.GetEnumeratorValues :
AstMethods.GetEnumeratorValuesNoComplexSets,
// arguments
Parent.LocalContext,
right_temp,
AstUtils.Constant(expected),
AstUtils.Constant(argcntafter)
)
), typeof(object[]));
// 4. Create temporary variable for the array
MSAst.ParameterExpression array_temp = Expression.Variable(typeof(object[]), "array");
// 5. Assign the value of the method call (mce) into the array temp
// And add the assignment "array_temp = Ops.GetEnumeratorValues(...)" into the block
MSAst.Expression assignStmt2 = MakeAssignment(
array_temp,
enumeratorValues,
rightSpan
);
ReadOnlyCollectionBuilder <MSAst.Expression> sets = new ReadOnlyCollectionBuilder <MSAst.Expression>(_items.Length + 1);
for (int i = 0; i < _items.Length; i++)
{
// target = array_temp[i]
Expression target = _items[i];
if (target == null)
{
continue;
}
// 6. array_temp[i]
MSAst.Expression element = Expression.ArrayAccess(
array_temp, // array expression
AstUtils.Constant(i) // index
);
// 7. target = array_temp[i], and add the transformed assignment into the list of sets
MSAst.Expression set = target.TransformSet(
emitIndividualSets ? // span
target.Span :
SourceSpan.None,
element,
PythonOperationKind.None
);
sets.Add(set);
}
// 9. add the sets as their own block so they can be marked as a single span, if necessary.
sets.Add(AstUtils.Empty());
MSAst.Expression itemSet = GlobalParent.AddDebugInfo(Expression.Block(sets.ToReadOnlyCollection()), leftSpan);
// 10. Return the suite statement (block)
return(GlobalParent.AddDebugInfo(Expression.Block(new[] { array_temp, right_temp }, assignStmt1, assignStmt2, itemSet, AstUtils.Empty()), totalSpan));
}
