Conversation
This lays the foundation for Cabal-exactprint to consume user comments.
The parser of the envelope format ("field parser") now annotates each of
the parsed fields with its preceding and succeeding comments, along with
the existing source location annotation 'Position'.
This change is orthogonal to the final chosen exactprint implementation,
or the algebra we use to modify existing fields and/or generate new
fields. Instead, it merely makes the user comments available to any
consumer that reads cabal fields, the envelope format.
readFields* functions now have their counterparts that parses with
comments, named readFieldsWithComments*.
leana8959
force-pushed
the
transform-fields-poc
branch
from
September 19, 2026 13:54
664a65e to
3dfb9a4
Compare
leana8959
force-pushed
the
transform-fields-poc
branch
2 times, most recently
from
September 22, 2026 17:14
f09cbf5 to
3e1d2f1
Compare
use transform example refactor modifying, take 1 refactor modifying, take 2 rename functions preverse correct starting position extract and restore comments edit target build depend example HasPos class print to stderr to avoid interleaving test editing make edit better implement relativization clean up relativization compute line position add new joining function rewrite transformation algebra use relative spacing in modification clean up, move Fields.Spacing to its own module clean up test suite include comment in relative spacing conversion checkpoint implement a simple renderer for Field ann initialize test for field exact rendering debug exact printer roundtrip is possible roundtrip poc Run cabal test Cabal-tests:hackage-tests --test-option="field-roundtrip" dump everything that don't match in exact print hackage test restore joining, ditch spacing experiments for now add naive tabs to space substitution, remove tracing demonstrate cabal project file roundtrip ignore stupid errors and focus on the real ones patch tabs -> space, empty lines, and lineendings drop empty lines at end of file retain position of colon This needs to be refined but it's the basic idea. make colon closest to field name and not separated by comments print failed filenames for further processing and investigation add a few examples for quotes apply hints rewrite exact printer with RWS remove irrelevant todo fix tests restore final trailing newline prevent memory leak print quotes add unit test for simple transformation implement modifyValueList remove useless instance add few new tests and CRLF support comment out traces implement splitBSAtPosition, add tests implement substituteSubBSAt fix off by one The way parsec combinators save position makes it save on the first and last char. We need to increment the position to make the end position exclusive. clean up joinFieldLine implementation, add tests test modifyValueList Located combinator will report the placement when the parser is done. If a parser consumes trailing spaces, it will report a ending position that is too far below. This is the case for dependency. fix off by one fix in list modification trailing list remove tracing split bytestring transformation from fieldlines implement tests for modifyValueAtomAlaBS rename functions test modification of strings at any position within a dependency list parameterize edit functions with lineending configuration run formatter add examples for stringy lists implement prepend item in list clean up modification framework to better match the proposal add simple modification framework tests field removal fix removal, add tested test add a line ending guessing function add todos fine grain adding/removing/modifying fix mapping functions doesn't really matter, we can just tell the user but maybe the open approach can allow user to do this. hmm. implement cascading to chain fallback edits rewrite in individual simple functions simplify function naming add todos rename configuration types edit distributivity add product operator add hasChanged assertion operator clean up todos create a concrete edit error type remove applicative instance remove temporary call to error implement fieldline splitting remove duplicated functions and newline handling We always split the lines to a field line, so we don't care use split fieldlines start implementing position fixing in addField fixes, complete add's position shifting fix one-indexed position, accept test result test AddStart as well implement position shifting in modifyField and modifySection remove ModifyAll mode add a modify test update substitute sub bytestring at tests Previously the ending was not inclusing, I must have changed how it works. add an integration test replace Newtype class with Coerce class fix newtype class in parser tests add a pass to turn name to lower case accept casing in concrete parsing document the reason of orFallback add comment handling in modification functions update comment handling in test suite add comment in example add export list to transform module make modifyValueList partial make modifyValueAtomAla partial allow using partial modification function in modify focuses add instances to fix test update todos remove project files add todos add export list for ExactPretty add proper position shifting logic in new field fix colonPos calculation remove todo add a basic add section function make prependValueListBS partial add a function to prepend function list move code around clean up imports implement example formatter to test out the idea add a function to run the formatter run the build-depends formatter as an example add shared context to edit functions move code around, remove dead code implement sectionArgBS refactor using monad instance run formatter liftA2 is cool move parsec orphan instance to its module update todo on labels reuse transform functions to format proper formatting example with multiple sections add modifyConfitionConfVar document position handling run formatter fix test suite add fields to example demonstrate printing rip out formatter poc This will be put into a separate PR for demonstration clean up warnings fix import run formatter fix lints fix conditional import fix compilation run formatter fix compilation warning fix whitespaces fix typos guard field concrete syntax annotation behind pattern synonyms fix doctests Revert "fix whitespaces" This reverts commit c53ef37. exclude golden test files from whitespace check restore poc version of transform.hs fix test compilation update test expectations fix validate fix linting remove use of foldl1' It uses Data.Foldable1 and is too recent, I don't want to do cpp guard pattern export behind CPP
leana8959
force-pushed
the
transform-fields-poc
branch
from
September 22, 2026 20:34
39207a9 to
061d8cb
Compare
Collaborator
|
To avoid the GHC parser failure, the whole export list can be disabled: |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
I made substantial progress in the exactprinter & modification framework describe in the proposal haskell/cabal-proposals#7. This branch/PR shows how it works.
The diff is roughly 2.5k (it's stacked on the #11252).
TL;DR: The exactprinter allows programmers to parse a fields file, and printed it back exactly the same (with the exception that we decided that trailing spaces will be discarded for now for a simple first implementation).
The modification framework allows users to modify values in the cabal fields tree in a typed manner.
In Cabal-tests/tests/ParserTests.hs you can find examples of how the API would look like.
I am planning to rewrite the modification framework with a
Relativemonad, so that the modification will only have to handle offsets, and changes become more composable. Absolute position will only need to be resolved in the end of the modification. This is not yet implemented.Please read Github PR Conventions and then fill in one of these two templates.
Template Α: This PR modifies behaviour or interface
Include the following checklist in your PR:
significance: significantin the changelog file.Template B: This PR does not modify behaviour or interface
E.g. the PR only touches documentation or tests, does refactorings, etc.
Include the following checklist in your PR: