1 files changed, 42 insertions, 0 deletions
diff --git a/starlark/debug.go b/starlark/debug.go
new file mode 100644
index 0000000..22a2124
--- /dev/null
+++ b/starlark/debug.go
@@ -0,0 +1,42 @@
+package starlark
+
+import "go.starlark.net/syntax"
+
+// This file defines an experimental API for the debugging tools.
+// Some of these declarations expose details of internal packages.
+// (The debugger makes liberal use of exported fields of unexported types.)
+// Breaking changes may occur without notice.
+
+// Local returns the value of the i'th local variable.
+// It may be nil if not yet assigned.
+//
+// Local may be called only for frames whose Callable is a *Function (a
+// function defined by Starlark source code), and only while the frame
+// is active; it will panic otherwise.
+//
+// This function is provided only for debugging tools.
+//
+// THIS API IS EXPERIMENTAL AND MAY CHANGE WITHOUT NOTICE.
+func (fr *frame) Local(i int) Value { return fr.locals[i] }
+
+// DebugFrame is the debugger API for a frame of the interpreter's call stack.
+//
+// Most applications have no need for this API; use CallFrame instead.
+//
+// Clients must not retain a DebugFrame nor call any of its methods once
+// the current built-in call has returned or execution has resumed
+// after a breakpoint as this may have unpredictable effects, including
+// but not limited to retention of object that would otherwise be garbage.
+type DebugFrame interface {
+	Callable() Callable        // returns the frame's function
+	Local(i int) Value         // returns the value of the (Starlark) frame's ith local variable
+	Position() syntax.Position // returns the current position of execution in this frame
+}
+
+// DebugFrame returns the debugger interface for
+// the specified frame of the interpreter's call stack.
+// Frame numbering is as for Thread.CallFrame.
+//
+// This function is intended for use in debugging tools.
+// Most applications should have no need for it; use CallFrame instead.
+func (thread *Thread) DebugFrame(depth int) DebugFrame { return thread.frameAt(depth) }