#2346 redone: a formatter for Rascal itself, plus the necessary improvements and stabilization in the Box formatter framework code. by jurgenvinju · Pull Request #2738 · usethesource/rascal

jurgenvinju · 2026-03-31T11:39:11Z

This is a redo of #2346 which was mangled due to a wrong use of git-filter-repo.

Rascal is a pretty big language so this pushes the new toBox and format and layoutDiff functions to the max.

The goal is to formulate toBox rules such that the formatter produces beautiful layout, and
We identify bugs and efficiency issues in toBox, format and layoutDiff and fix them immediately.
We add box operators with variable argument lists to eliminate a level of superfluous brackets
We test for exceptions, parse errors and comment preservation, on all files of the standard library and the larger files in the Compiler and checker.
re-implementation (optimized) of U and G
integration tests succeed https://github.com/usethesource/rascal-core-big-tests/actions/runs/23592431666

… the string literals

codecov · 2026-03-31T12:11:10Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 46%. Comparing base (f6d6bbe) to head (d0d02e0).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##              main   #2738   +/-   ##
=======================================
  Coverage       46%     46%           
- Complexity    6725    6732    +7     
=======================================
  Files          794     794           
  Lines        65923   65936   +13     
  Branches      9888    9888           
=======================================
+ Hits         30837   30853   +16     
+ Misses       32696   32693    -3     
  Partials      2390    2390

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…igate the loss of the automatic assert

jurgenvinju · 2026-04-19T11:05:22Z

thanks for the review @toinehartman . Before we merge, some of the TODOs @toinehartman highlighted should be checked. See the conversation above.

sonarqubecloud · 2026-04-20T10:31:38Z

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

jurgenvinju · 2026-04-21T08:31:41Z

@DavyLandman this seems ready. lots of fixes in Box-related code, fixed in layoutDif, and new features for Rascal formatting.

toinehartman

Nice to see the declarative formatting nearing completion! I just have some small remarks.

toinehartman · 2026-04-21T14:06:04Z

    // first add required locations to layout nodes
-    original = reposition(original, markLit=true, markLayout=true, markSubLayout=true);
+    // TODO: check if indeed repositioning is never needed
+    // original = reposition(original, markLit=true, markLayout=true, markSubLayout=true);


Can we do an remove this TODO?

toinehartman · 2026-04-21T14:10:14Z

 data Row = R(list[Box] cells);

+// Row R(Box cells...) = _R(cells);
+


Do we still need this?

toinehartman · 2026-04-21T14:12:56Z

+@pitfalls{
+* only useful for debugging purposes, because it becomes a pipeline bottleneck otherwise.
+}
+Box debUG(Box b) {


Is the name a funny play on the fact that this is used mostly with U and G boxes?

toinehartman · 2026-04-21T14:13:47Z

+    bool trimTrailingWhitespace = true,
+	bool insertFinalNewline = true,
+    bool trimFinalNewlines = true
+) = formattingOptions();


I really like this! Looking forward to plugging this into LSP as well.

toinehartman · 2026-04-21T14:22:34Z

+}
+
+Box toClusterBox(&T* lst, FO opts=fo()) = toClusterBox([e | e <- lst], opts=opts);
+Box toClusterBox(&T+ lst, FO opts=fo()) = toClusterBox([e | e <- lst], opts=opts);


Star and plus patterns? I learn something new every day...

toinehartman · 2026-04-21T14:23:15Z

 @synopsis{Convert the Rascal internal grammar representation format (Grammar) to 
  a syntax definition in Rascal source code.}
+@pitfalls{
+This function does not use advanced formatting feature because it is a part of


Suggested change

This function does not use advanced formatting feature because it is a part of

This function does not use advanced formatting features because it is a part of

toinehartman · 2026-04-21T14:23:58Z

+// Box toBox((Expression) `<Expression a> in <Expression b>`)
+//     = H1(HOV(toBox(a)), L("in"), HOV(toBox(b)));
+
+// Box toBox((Expression) `<Expression a> \<= <Expression b>`)
+//     = H1(HOV(toBox(a)), L("\<="), HOV(toBox(b)));
+
+// Box toBox((Expression) `<Expression a> \< <Expression b>`)
+//     = H1(HOV(toBox(a)), L("\<"), HOV(toBox(b)));
+
+// Box toBox((Expression) `<Expression a> == <Expression b>`)
+//     = H1(HOV(toBox(a)), L("=="), HOV(toBox(b)));
+
+// Box toBox((Expression) `<Expression a> \>= <Expression b>`)
+//     = H1(HOV(toBox(a)), L("\>="), HOV(toBox(b)));
+
+// Box toBox((Expression) `<Expression a> \> <Expression b>`)
+//     = H1(HOV(toBox(a)), L("\>"), HOV(toBox(b)));


Commented code; should we keep this?

toinehartman · 2026-04-21T14:25:19Z

Does this PR contain a bootstrap of the parser? If so, why?

toinehartman · 2026-04-21T14:30:07Z

+* will do nothing if the formatter breaks syntax rules or introduces ambiguity.
+* will never lose any comments.


toinehartman · 2026-04-21T14:31:28Z

+import IO;
+
+@synopsis{Styles for span classes generated by ((ToHTML))}
+public str ToHTMLStyle() =


Can we align this with the other names in this module?

Suggested change

public str ToHTMLStyle() =

public str toHTMLStyle() =

jurgenvinju added 2 commits March 31, 2026 13:38

bumped to 0.43.0 to have something to work with

b714065

merged PR #2346 into this one to clean up git-filter-repo mess

11943a8

jurgenvinju changed the title ~~Another clean PR branch to work with for the formatter"~~ Redo #2346 formatter branch Mar 31, 2026

jurgenvinju added 2 commits March 31, 2026 13:47

Update ErrorTreeSemanticsTests.rsc

06681f2

regenerated parser for rascal because constructor names were added in…

b9179bc

… the string literals

jurgenvinju added 8 commits March 31, 2026 14:13

fixed static errors

7a70844

fixed broken and ambiguous links in formatter docs

2169f61

fixes more links in doc

09321d6

Merge branch 'main' into second-try-rascal-formatter

a2db19c

added batch processing tools for formatters

c0b28b7

added voidJob functions for consistency and completeness sake

494155c

Merge branch 'main' into second-try-rascal-formatter

4748ac9

Merge branch 'main' into second-try-rascal-formatter

914b6a7

jurgenvinju mentioned this pull request Apr 7, 2026

Rascal formatter based on Box and layoutDiff, including upgrades of Tree2Box, Box2Text and layoutDiff #2346

Closed

6 tasks

toinehartman mentioned this pull request Apr 8, 2026

Parametric: formatting usethesource/rascal-language-servers#677

Draft

toinehartman reviewed Apr 8, 2026

View reviewed changes

jurgenvinju added 3 commits April 19, 2026 12:56

removed commented-out assert and added @pitfalls documentation to mit…

3c12b73

…igate the loss of the automatic assert

Change strip method to private default

27dc35a

Update documentation for IO.rsc

299d843

jurgenvinju added 5 commits April 19, 2026 13:05

Merge branch 'main' into second-try-rascal-formatter

f528caf

Update ExecuteTextEdits.rsc

b78aa0f

Fix typo in synopsis for ExecuteTextEdits.rsc

a5864e8

fixed tutor link

b7fc46a

cleaning up points pointed out by @toinehartman

d0d02e0

jurgenvinju changed the title ~~Redo #2346 formatter branch~~ #2346 redone: a formatter for Rascal itself, plus the necessary improvements and stabilization in the Box formatter framework code. Apr 20, 2026

jurgenvinju self-assigned this Apr 21, 2026

jurgenvinju added the enhancement label Apr 21, 2026

jurgenvinju added the library label Apr 21, 2026

jurgenvinju requested a review from DavyLandman April 21, 2026 08:30

toinehartman approved these changes Apr 21, 2026

View reviewed changes

		data Row = R(list[Box] cells);

		// Row R(Box cells...) = _R(cells);

	This function does not use advanced formatting feature because it is a part of
	This function does not use advanced formatting features because it is a part of

		* will do nothing if the formatter breaks syntax rules or introduces ambiguity.
		* will never lose any comments.

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sonarqubecloud Bot commented Apr 20, 2026

Quality Gate passed

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jurgenvinju commented Apr 21, 2026

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