Bug report

Bug description:

The issue happens only when pulling a line from history.

Typing 4 spaces or a Tab and hitting Enter when at the PDB prompt is interpreted the same as hitting Enter without entering whitespace.
However, grabbing a whitespace-only line from history causes a prompt/line continuatin.

To reproduce:

1. Type if True: and hit Enter
2. Type 4 spaces and hit Enter
3. Type 4 spaces, print("True") and hit Enter twice
4. Hit the up arrow 2 times
5. Hit Enter again

After those 5 steps you will see:

Repeatedly hitting Enter at that point shows the same continuation prompt:

The new REPL had a somewhat similar issue (#118911 was part of it).

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-125378: Trigger a repeat for the full multi-line statement for empty line command #125717
• [3.13] gh-125378: Trigger a repeat for the full multi-line statement for empty line command (GH-125717) #125736