Alternative fix for #205

[sjakobi]

I asked Codex to come up with an alternative to #282 for fixing #205.

I haven't looked at it very closely myself yet.

Notes from Codex:

• Findings
- #205 is not caused by the strict Int in SLine at prettyprinter/src/Prettyprinter/
Internal.hs:1669. The real problem is the eager case x of ... in the Line branch at
prettyprinter/src/Prettyprinter/Internal.hs:2076, because that forces the tail stream
while layoutSmart is still exploring alternatives.
- That also explains why only layoutSmart blows up: its fits predicate keeps walking across
multiple SLines at prettyprinter/src/Prettyprinter/Internal.hs:1995, while layoutPretty
stops at the first line break.
- I checked the old sjakobi/issue205 work:
- a61681e = “Remove bang on Int in SLine”
- ee48764 = revert of that change
- 2a18909 = full revert of #139
- Bench result with the exact issue reproducer, built -O2 with ghc-9.12.2:
- current master: n=30 -> 8.55s, n=33 -> timed out at 20s
- lazy-SLine variant: n=30 -> 8.66s, n=33 -> timed out at 20s
- full revert of #139: effectively instant
- So the “make the Int lazy” idea is dead: same asymptotics, same runtime.
Best Candidate
I prototyped a targeted fix in /tmp/pp-master-detached/prettyprinter/src/Prettyprinter/
Internal.hs:1981 without touching your main checkout:
- build layoutSmart with plain SLine i x again
- add a linear post-pass dropIndentationOnEmptyLines that only rewrites SLine i x to SLine 0
x when the transformed tail starts with SEmpty or another SLine
- keep layoutPretty and layoutUnbounded on the current behavior
- in layoutSmart.fits, only normalize blank-line indentation in the branch that was already
going to recurse
That prototype:
- fixes #205 immediately: n=30, 33, 40 all measured 0.00s
- preserves the #139 behavior
- avoids the overreach of removeTrailingWhitespace postprocessing
- passes the full testsuite via cabal test prettyprinter:testsuite --with-compiler=ghc-9.12
Other Options
- Full revert of #139: simplest, but reintroduces the old trailing-indentation regression.
- removeTrailingWhitespace after layoutSmart: fast and easy, but too aggressive; it strips
user-produced trailing spaces too.
- New SimpleDocStream constructor for deferred indentation: probably the cleanest long-term
design, but much more invasive.

[sjakobi]

I asked Codex to come up with an alternative to #282 for fixing #205.

I haven't looked at it very closely myself yet.

Notes from Codex:

• Findings
- #205 is not caused by the strict Int in SLine at prettyprinter/src/Prettyprinter/
Internal.hs:1669. The real problem is the eager case x of ... in the Line branch at
prettyprinter/src/Prettyprinter/Internal.hs:2076, because that forces the tail stream
while layoutSmart is still exploring alternatives.
- That also explains why only layoutSmart blows up: its fits predicate keeps walking across
multiple SLines at prettyprinter/src/Prettyprinter/Internal.hs:1995, while layoutPretty
stops at the first line break.
- I checked the old sjakobi/issue205 work:
- a61681e = “Remove bang on Int in SLine”
- ee48764 = revert of that change
- 2a18909 = full revert of #139
- Bench result with the exact issue reproducer, built -O2 with ghc-9.12.2:
- current master: n=30 -> 8.55s, n=33 -> timed out at 20s
- lazy-SLine variant: n=30 -> 8.66s, n=33 -> timed out at 20s
- full revert of #139: effectively instant
- So the “make the Int lazy” idea is dead: same asymptotics, same runtime.
Best Candidate
I prototyped a targeted fix in /tmp/pp-master-detached/prettyprinter/src/Prettyprinter/
Internal.hs:1981 without touching your main checkout:
- build layoutSmart with plain SLine i x again
- add a linear post-pass dropIndentationOnEmptyLines that only rewrites SLine i x to SLine 0
x when the transformed tail starts with SEmpty or another SLine
- keep layoutPretty and layoutUnbounded on the current behavior
- in layoutSmart.fits, only normalize blank-line indentation in the branch that was already
going to recurse
That prototype:
- fixes #205 immediately: n=30, 33, 40 all measured 0.00s
- preserves the #139 behavior
- avoids the overreach of removeTrailingWhitespace postprocessing
- passes the full testsuite via cabal test prettyprinter:testsuite --with-compiler=ghc-9.12
Other Options
- Full revert of #139: simplest, but reintroduces the old trailing-indentation regression.
- removeTrailingWhitespace after layoutSmart: fast and easy, but too aggressive; it strips
user-produced trailing spaces too.
- New SimpleDocStream constructor for deferred indentation: probably the cleanest long-term
design, but much more invasive.

[sjakobi]

I asked Codex to come up with an alternative to #282 for fixing #205.

I haven't looked at it very closely myself yet.

Notes from Codex:

• Findings
- #205 is not caused by the strict Int in SLine at prettyprinter/src/Prettyprinter/
Internal.hs:1669. The real problem is the eager case x of ... in the Line branch at
prettyprinter/src/Prettyprinter/Internal.hs:2076, because that forces the tail stream
while layoutSmart is still exploring alternatives.
- That also explains why only layoutSmart blows up: its fits predicate keeps walking across
multiple SLines at prettyprinter/src/Prettyprinter/Internal.hs:1995, while layoutPretty
stops at the first line break.
- I checked the old sjakobi/issue205 work:
- a61681e = “Remove bang on Int in SLine”
- ee48764 = revert of that change
- 2a18909 = full revert of #139
- Bench result with the exact issue reproducer, built -O2 with ghc-9.12.2:
- current master: n=30 -> 8.55s, n=33 -> timed out at 20s
- lazy-SLine variant: n=30 -> 8.66s, n=33 -> timed out at 20s
- full revert of #139: effectively instant
- So the “make the Int lazy” idea is dead: same asymptotics, same runtime.
Best Candidate
I prototyped a targeted fix in /tmp/pp-master-detached/prettyprinter/src/Prettyprinter/
Internal.hs:1981 without touching your main checkout:
- build layoutSmart with plain SLine i x again
- add a linear post-pass dropIndentationOnEmptyLines that only rewrites SLine i x to SLine 0
x when the transformed tail starts with SEmpty or another SLine
- keep layoutPretty and layoutUnbounded on the current behavior
- in layoutSmart.fits, only normalize blank-line indentation in the branch that was already
going to recurse
That prototype:
- fixes #205 immediately: n=30, 33, 40 all measured 0.00s
- preserves the #139 behavior
- avoids the overreach of removeTrailingWhitespace postprocessing
- passes the full testsuite via cabal test prettyprinter:testsuite --with-compiler=ghc-9.12
Other Options
- Full revert of #139: simplest, but reintroduces the old trailing-indentation regression.
- removeTrailingWhitespace after layoutSmart: fast and easy, but too aggressive; it strips
user-produced trailing spaces too.
- New SimpleDocStream constructor for deferred indentation: probably the cleanest long-term
design, but much more invasive.

[sjakobi]

I asked Codex to come up with an alternative to #282 for fixing #205.

I haven't looked at it very closely myself yet.

Notes from Codex:

• Findings
- #205 is not caused by the strict Int in SLine at prettyprinter/src/Prettyprinter/
Internal.hs:1669. The real problem is the eager case x of ... in the Line branch at
prettyprinter/src/Prettyprinter/Internal.hs:2076, because that forces the tail stream
while layoutSmart is still exploring alternatives.
- That also explains why only layoutSmart blows up: its fits predicate keeps walking across
multiple SLines at prettyprinter/src/Prettyprinter/Internal.hs:1995, while layoutPretty
stops at the first line break.
- I checked the old sjakobi/issue205 work:
- a61681e = “Remove bang on Int in SLine”
- ee48764 = revert of that change
- 2a18909 = full revert of #139
- Bench result with the exact issue reproducer, built -O2 with ghc-9.12.2:
- current master: n=30 -> 8.55s, n=33 -> timed out at 20s
- lazy-SLine variant: n=30 -> 8.66s, n=33 -> timed out at 20s
- full revert of #139: effectively instant
- So the “make the Int lazy” idea is dead: same asymptotics, same runtime.
Best Candidate
I prototyped a targeted fix in /tmp/pp-master-detached/prettyprinter/src/Prettyprinter/
Internal.hs:1981 without touching your main checkout:
- build layoutSmart with plain SLine i x again
- add a linear post-pass dropIndentationOnEmptyLines that only rewrites SLine i x to SLine 0
x when the transformed tail starts with SEmpty or another SLine
- keep layoutPretty and layoutUnbounded on the current behavior
- in layoutSmart.fits, only normalize blank-line indentation in the branch that was already
going to recurse
That prototype:
- fixes #205 immediately: n=30, 33, 40 all measured 0.00s
- preserves the #139 behavior
- avoids the overreach of removeTrailingWhitespace postprocessing
- passes the full testsuite via cabal test prettyprinter:testsuite --with-compiler=ghc-9.12
Other Options
- Full revert of #139: simplest, but reintroduces the old trailing-indentation regression.
- removeTrailingWhitespace after layoutSmart: fast and easy, but too aggressive; it strips
user-produced trailing spaces too.
- New SimpleDocStream constructor for deferred indentation: probably the cleanest long-term
design, but much more invasive.

[sjakobi]

I asked Codex to come up with an alternative to #282 for fixing #205.

I haven't looked at it very closely myself yet.

Notes from Codex:

• Findings
- #205 is not caused by the strict Int in SLine at prettyprinter/src/Prettyprinter/
Internal.hs:1669. The real problem is the eager case x of ... in the Line branch at
prettyprinter/src/Prettyprinter/Internal.hs:2076, because that forces the tail stream
while layoutSmart is still exploring alternatives.
- That also explains why only layoutSmart blows up: its fits predicate keeps walking across
multiple SLines at prettyprinter/src/Prettyprinter/Internal.hs:1995, while layoutPretty
stops at the first line break.
- I checked the old sjakobi/issue205 work:
- a61681e = “Remove bang on Int in SLine”
- ee48764 = revert of that change
- 2a18909 = full revert of #139
- Bench result with the exact issue reproducer, built -O2 with ghc-9.12.2:
- current master: n=30 -> 8.55s, n=33 -> timed out at 20s
- lazy-SLine variant: n=30 -> 8.66s, n=33 -> timed out at 20s
- full revert of #139: effectively instant
- So the “make the Int lazy” idea is dead: same asymptotics, same runtime.
Best Candidate
I prototyped a targeted fix in /tmp/pp-master-detached/prettyprinter/src/Prettyprinter/
Internal.hs:1981 without touching your main checkout:
- build layoutSmart with plain SLine i x again
- add a linear post-pass dropIndentationOnEmptyLines that only rewrites SLine i x to SLine 0
x when the transformed tail starts with SEmpty or another SLine
- keep layoutPretty and layoutUnbounded on the current behavior
- in layoutSmart.fits, only normalize blank-line indentation in the branch that was already
going to recurse
That prototype:
- fixes #205 immediately: n=30, 33, 40 all measured 0.00s
- preserves the #139 behavior
- avoids the overreach of removeTrailingWhitespace postprocessing
- passes the full testsuite via cabal test prettyprinter:testsuite --with-compiler=ghc-9.12
Other Options
- Full revert of #139: simplest, but reintroduces the old trailing-indentation regression.
- removeTrailingWhitespace after layoutSmart: fast and easy, but too aggressive; it strips
user-produced trailing spaces too.
- New SimpleDocStream constructor for deferred indentation: probably the cleanest long-term
design, but much more invasive.

[sjakobi]

I asked Codex to come up with an alternative to #282 for fixing #205.

I haven't looked at it very closely myself yet.

Notes from Codex:

• Findings
- #205 is not caused by the strict Int in SLine at prettyprinter/src/Prettyprinter/
Internal.hs:1669. The real problem is the eager case x of ... in the Line branch at
prettyprinter/src/Prettyprinter/Internal.hs:2076, because that forces the tail stream
while layoutSmart is still exploring alternatives.
- That also explains why only layoutSmart blows up: its fits predicate keeps walking across
multiple SLines at prettyprinter/src/Prettyprinter/Internal.hs:1995, while layoutPretty
stops at the first line break.
- I checked the old sjakobi/issue205 work:
- a61681e = “Remove bang on Int in SLine”
- ee48764 = revert of that change
- 2a18909 = full revert of #139
- Bench result with the exact issue reproducer, built -O2 with ghc-9.12.2:
- current master: n=30 -> 8.55s, n=33 -> timed out at 20s
- lazy-SLine variant: n=30 -> 8.66s, n=33 -> timed out at 20s
- full revert of #139: effectively instant
- So the “make the Int lazy” idea is dead: same asymptotics, same runtime.
Best Candidate
I prototyped a targeted fix in /tmp/pp-master-detached/prettyprinter/src/Prettyprinter/
Internal.hs:1981 without touching your main checkout:
- build layoutSmart with plain SLine i x again
- add a linear post-pass dropIndentationOnEmptyLines that only rewrites SLine i x to SLine 0
x when the transformed tail starts with SEmpty or another SLine
- keep layoutPretty and layoutUnbounded on the current behavior
- in layoutSmart.fits, only normalize blank-line indentation in the branch that was already
going to recurse
That prototype:
- fixes #205 immediately: n=30, 33, 40 all measured 0.00s
- preserves the #139 behavior
- avoids the overreach of removeTrailingWhitespace postprocessing
- passes the full testsuite via cabal test prettyprinter:testsuite --with-compiler=ghc-9.12
Other Options
- Full revert of #139: simplest, but reintroduces the old trailing-indentation regression.
- removeTrailingWhitespace after layoutSmart: fast and easy, but too aggressive; it strips
user-produced trailing spaces too.
- New SimpleDocStream constructor for deferred indentation: probably the cleanest long-term
design, but much more invasive.

[sjakobi]

I asked Codex to come up with an alternative to #282 for fixing #205.

I haven't looked at it very closely myself yet.

Notes from Codex:

• Findings
- #205 is not caused by the strict Int in SLine at prettyprinter/src/Prettyprinter/
Internal.hs:1669. The real problem is the eager case x of ... in the Line branch at
prettyprinter/src/Prettyprinter/Internal.hs:2076, because that forces the tail stream
while layoutSmart is still exploring alternatives.
- That also explains why only layoutSmart blows up: its fits predicate keeps walking across
multiple SLines at prettyprinter/src/Prettyprinter/Internal.hs:1995, while layoutPretty
stops at the first line break.
- I checked the old sjakobi/issue205 work:
- a61681e = “Remove bang on Int in SLine”
- ee48764 = revert of that change
- 2a18909 = full revert of #139
- Bench result with the exact issue reproducer, built -O2 with ghc-9.12.2:
- current master: n=30 -> 8.55s, n=33 -> timed out at 20s
- lazy-SLine variant: n=30 -> 8.66s, n=33 -> timed out at 20s
- full revert of #139: effectively instant
- So the “make the Int lazy” idea is dead: same asymptotics, same runtime.
Best Candidate
I prototyped a targeted fix in /tmp/pp-master-detached/prettyprinter/src/Prettyprinter/
Internal.hs:1981 without touching your main checkout:
- build layoutSmart with plain SLine i x again
- add a linear post-pass dropIndentationOnEmptyLines that only rewrites SLine i x to SLine 0
x when the transformed tail starts with SEmpty or another SLine
- keep layoutPretty and layoutUnbounded on the current behavior
- in layoutSmart.fits, only normalize blank-line indentation in the branch that was already
going to recurse
That prototype:
- fixes #205 immediately: n=30, 33, 40 all measured 0.00s
- preserves the #139 behavior
- avoids the overreach of removeTrailingWhitespace postprocessing
- passes the full testsuite via cabal test prettyprinter:testsuite --with-compiler=ghc-9.12
Other Options
- Full revert of #139: simplest, but reintroduces the old trailing-indentation regression.
- removeTrailingWhitespace after layoutSmart: fast and easy, but too aggressive; it strips
user-produced trailing spaces too.
- New SimpleDocStream constructor for deferred indentation: probably the cleanest long-term
design, but much more invasive.

[sjakobi]

I asked Codex to come up with an alternative to #282 for fixing #205.

I haven't looked at it very closely myself yet.

Notes from Codex:

• Findings
- #205 is not caused by the strict Int in SLine at prettyprinter/src/Prettyprinter/
Internal.hs:1669. The real problem is the eager case x of ... in the Line branch at
prettyprinter/src/Prettyprinter/Internal.hs:2076, because that forces the tail stream
while layoutSmart is still exploring alternatives.
- That also explains why only layoutSmart blows up: its fits predicate keeps walking across
multiple SLines at prettyprinter/src/Prettyprinter/Internal.hs:1995, while layoutPretty
stops at the first line break.
- I checked the old sjakobi/issue205 work:
- a61681e = “Remove bang on Int in SLine”
- ee48764 = revert of that change
- 2a18909 = full revert of #139
- Bench result with the exact issue reproducer, built -O2 with ghc-9.12.2:
- current master: n=30 -> 8.55s, n=33 -> timed out at 20s
- lazy-SLine variant: n=30 -> 8.66s, n=33 -> timed out at 20s
- full revert of #139: effectively instant
- So the “make the Int lazy” idea is dead: same asymptotics, same runtime.
Best Candidate
I prototyped a targeted fix in /tmp/pp-master-detached/prettyprinter/src/Prettyprinter/
Internal.hs:1981 without touching your main checkout:
- build layoutSmart with plain SLine i x again
- add a linear post-pass dropIndentationOnEmptyLines that only rewrites SLine i x to SLine 0
x when the transformed tail starts with SEmpty or another SLine
- keep layoutPretty and layoutUnbounded on the current behavior
- in layoutSmart.fits, only normalize blank-line indentation in the branch that was already
going to recurse
That prototype:
- fixes #205 immediately: n=30, 33, 40 all measured 0.00s
- preserves the #139 behavior
- avoids the overreach of removeTrailingWhitespace postprocessing
- passes the full testsuite via cabal test prettyprinter:testsuite --with-compiler=ghc-9.12
Other Options
- Full revert of #139: simplest, but reintroduces the old trailing-indentation regression.
- removeTrailingWhitespace after layoutSmart: fast and easy, but too aggressive; it strips
user-produced trailing spaces too.
- New SimpleDocStream constructor for deferred indentation: probably the cleanest long-term
design, but much more invasive.