gh-130698: Add safe methods to get prompts for new REPL #131110

sergey-miryanov · 2025-03-11T20:06:25Z

It fixes cases when ps1, ps2, ps3, ps4 raise exception from __str__.

~~This PR still misses tests for Reader.arg, but maybe you can review the whole solution - do I drive in the right direction?~~
Fixed for Reader.arg.

Issue: REPL exits with traceback when str(sys.ps1) raises #130698

- and for `unrecoverable` exceptions

Lib/_pyrepl/reader.py

tomasr8 · 2025-04-19T08:02:01Z

Lib/_pyrepl/utils.py

+DEFAULT_PS1 = ">>> "
+DEFAULT_PS2 = "... "
+DEFAULT_PS3 = "... "
+DEFAULT_PS4 = "... "


Should these match?

cpython/Lib/_pyrepl/reader.py

Lines 196 to 199 in 95800fe

ps1: str = "->> "

ps2: str = "/>> "

ps3: str = "|.. "

ps4: str = R"\__ "

No, I believe this is should be like:

DEFAULT_PS1 = ">>> " DEFAULT_PS2 = ">>> " DEFAULT_PS3 = "... " DEFAULT_PS4 = "... "

I had misread this

cpython/Lib/_pyrepl/reader.py

Lines 171 to 179 in 71da68d

* ps1, ps2, ps3, ps4:

prompts. ps1 is the prompt for a one-line input; for a

multiline input it looks like:

ps2> first line of input goes here

ps3> second and further

ps3> lines get ps3

...

ps4> and the last one gets ps4

As with the usual top-level, you can set these to instances if

tomasr8 · 2025-04-19T08:39:24Z

Lib/test/test_pyrepl/test_reader.py

+        def prepare_reader_keep_prompts(*args, **kwargs):
+            reader = prepare_reader(*args, **kwargs)
+            del reader.get_prompt
+            reader.ps1 = Prompt()
+            reader.ps2 = "... "
+            reader.ps3 = "... "
+            reader.ps4 = ""
+            reader.can_colorize = False
+            reader.paste_mode = False
+            return reader
+
+        events = code_to_events("a=1")
+        reader, _ = handle_events_narrow_console(
+            events,
+            prepare_reader=prepare_reader_keep_prompts,
+        )


We could use a slightly simpler setup code:

Suggested change

def prepare_reader_keep_prompts(*args, **kwargs):

reader = prepare_reader(*args, **kwargs)

del reader.get_prompt

reader.ps1 = Prompt()

reader.ps2 = "... "

reader.ps3 = "... "

reader.ps4 = ""

reader.can_colorize = False

reader.paste_mode = False

return reader

events = code_to_events("a=1")

reader, _ = handle_events_narrow_console(

events,

prepare_reader=prepare_reader_keep_prompts,

)

def prepare_reader(events):

console = FakeConsole(events)

config = ReadlineConfig(readline_completer=None)

reader = ReadlineAlikeReader(console=console, config=config)

reader.can_colorize = False

return reader

events = code_to_events("if some_condition:\nsome_function()")

reader = prepare_reader(events)

Unfortunately this doesn't simplify code. I have added more simpler one on my sight. Note, we should use handle_all_events (or handle_events_narrow_console) to process whole input string and get it in the reader.buffer to check if '\n' contains or not in buffer.

Misc/NEWS.d/next/Library/2025-03-13-00-39-54.gh-issue-130698.o2aU3e.rst

…2aU3e.rst Co-authored-by: Tomas R. <tomas.roun8@gmail.com>

# Conflicts: # Lib/_pyrepl/reader.py

…gey-miryanov/cpython into pythongh-130698-pyrepl-ps1-exception

chris-eibl · 2025-04-20T06:46:38Z

Lib/_pyrepl/utils.py

@@ -10,6 +10,12 @@
 ZERO_WIDTH_TRANS = str.maketrans({"\x01": "", "\x02": ""})


+DEFAULT_PS1 = ">>> "
+DEFAULT_PS2 = ">>> "


Suggested change

DEFAULT_PS2 = ">>> "

DEFAULT_PS2 = "... "

See https://docs.python.org/3/library/sys.html#sys.ps1

sys.ps1
sys.ps2
Strings specifying the primary and secondary prompt of the interpreter. These are only defined if the interpreter is in interactive mode. Their initial values in this case are '>>> ' and '... '.

>>> import sys >>> sys.ps1 '>>> ' >>> sys.ps2 '... ' >>> def foo(): ... pass

Maybe here the DEFAULT_PS* shall be used, too? Are there more places?

cpython/Lib/_pyrepl/simple_interact.py

Lines 134 to 135 in 246ed23

ps1 = getattr(sys, "ps1", ">>> ")

ps2 = getattr(sys, "ps2", "... ")

IMHO, the comment in reader.py ~~is wrong~~ (or at least confusing):

cpython/Lib/_pyrepl/reader.py

Lines 171 to 178 in 246ed23

* ps1, ps2, ps3, ps4:

prompts. ps1 is the prompt for a one-line input; for a

multiline input it looks like:

ps2> first line of input goes here

ps3> second and further

ps3> lines get ps3

...

ps4> and the last one gets ps4

As @tomasr8 pointed above

cpython/Lib/_pyrepl/reader.py

Lines 196 to 199 in 95800fe

ps1: str = "->> "

ps2: str = "/>> "

ps3: str = "|.. "

ps4: str = R"\__ "

there are different defaults too. So IDK what is really default :)

Maybe here the DEFAULT_PS* shall be used, too? Are there more places?

Yes, but I'm not sure that usage of DEFAULT_PS* approved overall.

IDK either, but IMHO we should stick with what is documented and the status quo, i.e. DEFAULT_PS2 = "... ".

The reason why

cpython/Lib/_pyrepl/reader.py

Lines 196 to 199 in 95800fe

ps1: str = "->> "

ps2: str = "/>> "

ps3: str = "|.. "

ps4: str = R"\__ "

is not in effect:

cpython/Lib/_pyrepl/main.py

Lines 49 to 54 in 95800fe

# set sys.{ps1,ps2} just before invoking the interactive interpreter. This

# mimics what CPython does in pythonrun.c

if not hasattr(sys, "ps1"):

sys.ps1 = ">>> "

if not hasattr(sys, "ps2"):

sys.ps2 = "... "

and then later

cpython/Lib/_pyrepl/simple_interact.py

Lines 134 to 139 in 246ed23

ps1 = getattr(sys, "ps1", ">>> ")

ps2 = getattr(sys, "ps2", "... ")

try:

statement = multiline_input(more_lines, ps1, ps2)

except EOFError:

break

and then

cpython/Lib/_pyrepl/readline.py

Lines 375 to 387 in 95800fe

def multiline_input(self, more_lines: MoreLinesCallable, ps1: str, ps2: str) -> str:

"""Read an input on possibly multiple lines, asking for more

lines as long as 'more_lines(unicodetext)' returns an object whose

boolean value is true.

"""

reader = self.get_reader()

saved = reader.more_lines

try:

reader.more_lines = more_lines

reader.ps1 = ps1

reader.ps2 = ps1

reader.ps3 = ps2

reader.ps4 = ""

So IMHO we should consistently use DEFAULT_PS1 and DEFAULT_PS2 in those code parts above, but let @pablogsal decide on it.

Moreover, this part

reader.ps1 = ps1 reader.ps2 = ps1 reader.ps3 = ps2

IMHO explains this confusion

cpython/Lib/_pyrepl/reader.py

Lines 171 to 178 in 246ed23

* ps1, ps2, ps3, ps4:

prompts. ps1 is the prompt for a one-line input; for a

multiline input it looks like:

ps2> first line of input goes here

ps3> second and further

ps3> lines get ps3

...

ps4> and the last one gets ps4

ISTM, this is an implementation detail, and ps2=ps1, etc, maps to what we are used to in the cPython REPL.

Most probably, because the new PYREPL comes from PyPy?

Moreover, this part

Yeah, I saw this and this is a reason that I changed DEFAULT_PS2 yesterday.

Most probably, because the new PYREPL comes from PyPy?

I'm not familiar with PyPy, so 🤷‍♂️

Lib/_pyrepl/reader.py

Co-authored-by: Chris Eibl <138194463+chris-eibl@users.noreply.github.com>

pythongh-130698: Add safe methods to get prompts for new REPL

7e633d7

sergey-miryanov requested review from pablogsal, lysnikolaou and ambv as code owners March 11, 2025 20:06

bedevere-app bot added the awaiting review label Mar 11, 2025

bedevere-app bot mentioned this pull request Mar 11, 2025

REPL exits with traceback when str(sys.ps1) raises #130698

Open

sergey-miryanov added 4 commits March 12, 2025 01:13

Fix missing types

707bd38

Fix handling of arg prompt and add tests for it

ab84ee6

- and for `unrecoverable` exceptions

Make mypy happy again

5d91db7

Add news entry

e0b474b

tomasr8 reviewed Apr 19, 2025

View reviewed changes

sergey-miryanov and others added 6 commits April 20, 2025 00:54

Update Misc/NEWS.d/next/Library/2025-03-13-00-39-54.gh-issue-130698.o…

02e7e84

…2aU3e.rst Co-authored-by: Tomas R. <tomas.roun8@gmail.com>

Merge branch 'main' into pythongh-130698-pyrepl-ps1-exception

c68a695

# Conflicts: # Lib/_pyrepl/reader.py

Merge branch 'pythongh-130698-pyrepl-ps1-exception' of github.com:ser…

5293313

…gey-miryanov/cpython into pythongh-130698-pyrepl-ps1-exception

Simplify tests for reader with buggy prompt

4fc6853

Fix DEFAULT_PS2 string

ba8633b

Make __get_prompt_str less stricter

cac161d

chris-eibl reviewed Apr 20, 2025

View reviewed changes

Lib/_pyrepl/reader.py Outdated Show resolved Hide resolved

Update docstring for __get_prompt_str

60c189f

Co-authored-by: Chris Eibl <138194463+chris-eibl@users.noreply.github.com>

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gh-130698: Add safe methods to get prompts for new REPL #131110

gh-130698: Add safe methods to get prompts for new REPL #131110

sergey-miryanov commented Mar 11, 2025 •

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tomasr8 Apr 19, 2025

sergey-miryanov Apr 19, 2025

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sergey-miryanov Apr 19, 2025

chris-eibl Apr 20, 2025 •

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chris-eibl Apr 20, 2025

chris-eibl Apr 20, 2025

sergey-miryanov Apr 20, 2025

	ps1: str = "->> "
	ps2: str = "/>> "
	ps3: str = "\|.. "
	ps4: str = R"\__ "

	* ps1, ps2, ps3, ps4:
	prompts. ps1 is the prompt for a one-line input; for a
	multiline input it looks like:
	ps2> first line of input goes here
	ps3> second and further
	ps3> lines get ps3
	...
	ps4> and the last one gets ps4
	As with the usual top-level, you can set these to instances if

	ps1 = getattr(sys, "ps1", ">>> ")
	ps2 = getattr(sys, "ps2", "... ")

	# set sys.{ps1,ps2} just before invoking the interactive interpreter. This
	# mimics what CPython does in pythonrun.c
	if not hasattr(sys, "ps1"):
	sys.ps1 = ">>> "
	if not hasattr(sys, "ps2"):
	sys.ps2 = "... "

	ps1 = getattr(sys, "ps1", ">>> ")
	ps2 = getattr(sys, "ps2", "... ")
	try:
	statement = multiline_input(more_lines, ps1, ps2)
	except EOFError:
	break

	def multiline_input(self, more_lines: MoreLinesCallable, ps1: str, ps2: str) -> str:
	"""Read an input on possibly multiple lines, asking for more
	lines as long as 'more_lines(unicodetext)' returns an object whose
	boolean value is true.
	"""
	reader = self.get_reader()
	saved = reader.more_lines
	try:
	reader.more_lines = more_lines
	reader.ps1 = ps1
	reader.ps2 = ps1
	reader.ps3 = ps2
	reader.ps4 = ""

gh-130698: Add safe methods to get prompts for new REPL #131110

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sergey-miryanov commented Mar 11, 2025 •

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