Formatter poc - #12319
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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*.
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
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This is a proof of concept of an alternative formatter in cabal by implementing a third instance of
FieldGrammar, stacked on top of the exactprinting framework. By doing so we get for free, functions that format each FieldLine according to the type they should be parse/printed with.This formatter has interesting properties: it doesn't fuse in common stanzas.
Comments are not handled at the moment but it can be done in the future. We just need to agree on a sensible way to interleave comments with rerendered data.
In
Cabal-syntax/src/Distribution/PackageDescription/Format.hsyou can see how to define a formatter using existing field grammar for each section. InCabal-tests/tests/ParserTests/format-printed/simple_buildinfo.expryou will find the printed version (in golden file expression) ofCabal-tests/tests/ParserTests/format-printed/simple.cabal. No outer structure is changed, only the values.In
Cabal-syntax/src/Distribution/FieldGrammar/Format.hsyou can find the new formatter instance. It is very simple and serves as a shim layer to recover type information associated with each field name in FieldGrammar definitions.No new
ParsecorPrettyinstances need to be written, they are already there and their existence is enforced by the compiler.What's left to do to make this good:
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