[New-bugs-announce] [issue34055] IDLE inserts extra blank line in prompt after SyntaxError

[Grant Jenks]

New submission from Grant Jenks <grant.jenks at gmail.com>:

IDLE inserts an extra blank line after the prompt after encountering a SyntaxError:

```
>>> 1 + 2
3
>>> print('Hello')
Hello
                                     v-- Missing single quote!
>>> d = {1: 'uno', 2: 'dos', 3: 'tres}
	 
SyntaxError: EOL while scanning string literal
>>> print('Hello')
	 <-- Extra blank line and whitespace (tab and space).
Hello
>>> 1 + 2
	 <-- Extra blank line and whitespace (tab and space).
3
>>> 
```

Notice the line starting with ">>> d =" above contains a missing single quote which causes a "SyntaxError: EOL while scanning string literal". This causes IDLE to insert extra blank lines with one tab and one space after every input.

The old behavior looked like:

```
>>> 1 + 2
3
>>> print('Hello')
Hello
>>> d = {1: 'uno', 2: 'dos', 3: 'tres}
     
SyntaxError: EOL while scanning string literal
>>> print('Hello')
Hello
>>> 1 + 2
3
```

----------
assignee: terry.reedy
components: IDLE
messages: 321126
nosy: grantjenks, terry.reedy
priority: normal
severity: normal
status: open
title: IDLE inserts extra blank line in prompt after SyntaxError
type: behavior
versions: Python 3.6

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34055>
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