public bool ExtractMethod(IExtractMethodInput input)
{
// tighten up the selection so that we don't expand into any enclosing nodes because we overlap w/ their white space...
var selectionStart = _view.Selection.Start.Position;
while (selectionStart.Position < _view.TextBuffer.CurrentSnapshot.Length && Char.IsWhiteSpace(selectionStart.GetChar()))
{
selectionStart += 1;
}
var selectionEnd = _view.Selection.End.Position;
if (selectionEnd.Position == _view.TextBuffer.CurrentSnapshot.Length)
{
selectionEnd -= 1;
}
while (selectionEnd.Position >= 0 && Char.IsWhiteSpace(selectionEnd.GetChar()))
{
selectionEnd -= 1;
}
var walker = new EnclosingNodeWalker(_ast, selectionStart, selectionEnd);
_ast.Walk(walker);
Debug.Assert(walker.Target != null);
if (walker.Target == null)
{
return(false);
}
// expand the selection if we aren't currently covering a full expression/statement
if (!walker.Target.IsValidSelection ||
(WasSelectionExpanded(walker.Target, selectionStart, selectionEnd) && !input.ShouldExpandSelection()))
{
return(false);
}
_view.Selection.Select(
new SnapshotSpan(
_view.TextBuffer.CurrentSnapshot,
Span.FromBounds(
walker.Target.StartIncludingIndentation,
walker.Target.End
)
),
false
);
// check for things we cannot handle
if (!IsValidExtraction(input, walker.Target))
{
return(false);
}
// get the variables which are read by the selected statement(s)
var varCollector = new InnerVariableWalker(_ast);
walker.Target.Walk(varCollector);
// Walk the target to understand flow control and definite assignment to further understand
// what we need to flow in. For example if a variable is assigned to both in the un-extracted
// and extracted code but it's definitely assigned in the extracted code then we don't need
// to flow the variable in.
// Run flow checker, first on any nested scopes...
foreach (ScopeStatement scope in varCollector._scopes)
{
FlowChecker.Check(scope);
}
// then on our extracted code
var parent = walker.Target.Parents[walker.Target.Parents.Length - 1];
HashSet <PythonVariable> readBeforeInit;
FlowChecker extractedChecker = null;
if (parent.ScopeVariables != null)
{
extractedChecker = new FlowChecker(parent);
walker.Target.Walk(extractedChecker);
readBeforeInit = extractedChecker.ReadBeforeInitializedVariables;
}
else
{
readBeforeInit = new HashSet <PythonVariable>();
}
// then on code which follows our extracted body
var afterStmts = walker.Target.GetStatementsAfter(_ast);
HashSet <PythonVariable> readByFollowingCodeBeforeInit = null;
var parentNode = walker.Target.Parents[walker.Target.Parents.Length - 1];
var outputVars = new HashSet <PythonVariable>();
if (parentNode.ScopeVariables != null)
{
var checker = new FlowChecker(parentNode);
foreach (var afterStmt in afterStmts)
{
afterStmt.Walk(checker);
}
readByFollowingCodeBeforeInit = checker.ReadBeforeInitializedVariables;
foreach (var variable in varCollector._allWrittenVariables)
{
if (variable != null && variable.Scope is PythonAst)
{
// global variable assigned to in outer scope, and left with
// a valid value (not deleted) from the extracted code. We
// need to pass the value back out and assign to it in the
// global scope.
if (!checker.IsInitialized(variable) &&
extractedChecker.IsAssigned(variable))
{
outputVars.Add(variable);
}
}
}
}
// collect any nested scopes, and see if they read any free variables
var scopeCollector = new ScopeCollector();
foreach (var afterStmt in afterStmts)
{
afterStmt.Walk(scopeCollector);
}
foreach (var scope in scopeCollector._scopes)
{
if (scope.FreeVariables != null)
{
foreach (var freeVar in scope.FreeVariables)
{
if (varCollector._allWrittenVariables.Contains(freeVar))
{
// we've assigned to a variable accessed from an inner
// scope, we need to get the value of the variable back out.
outputVars.Add(freeVar);
}
}
}
}
// discover any variables which are consumed and need to be available as outputs...
var outputCollector = new OuterVariableWalker(_ast, walker.Target, varCollector, readBeforeInit, readByFollowingCodeBeforeInit, outputVars);
_ast.Walk(outputCollector);
if (outputCollector._outputVars.Count > 0 &&
walker.Target.ContainsReturn)
{
input.CannotExtract("Cannot extract method that assigns to variables and returns");
return(false);
}
var creator = new ExtractedMethodCreator(
_ast,
walker.Target.Parents,
outputCollector._inputVars,
outputCollector._outputVars,
walker.Target,
_view.Options.GetIndentSize(),
!_view.Options.IsConvertTabsToSpacesEnabled(),
_view.Options.GetNewLineCharacter()
);
var info = input.GetExtractionInfo(creator);
if (info == null)
{
// user cancelled extract method
return(false);
}
// get the new method body...
var newMethod = creator.GetExtractionResult(info);
// generate the call site.
using (var edit = _view.TextBuffer.CreateEdit()) {
// delete the selected code
int start = _view.Selection.Start.Position;
edit.Delete(Span.FromBounds(_view.Selection.Start.Position, _view.Selection.End.Position));
// insert the newly generated method
edit.Insert(walker.Target.InsertLocations[info.TargetScope], newMethod.Method);
// insert the call to the new method
edit.Insert(start, newMethod.Call);
edit.Apply();
}
return(true);
}