CHANGES:

• Add support for OCaml 5.5 (#622, @patricoferris, @NathanReb)

• Add support for OCaml 5.4 bivariant type parameters, they can now be used
  alongside ppx-es. (#629, @NathanReb)

• Add Attribute.Floating.declare_with_attr_loc and .declare_with_name_loc,
  by analogy to the same functions at top level of Attribute. (#631, @ceastlund)

• Migrate Ptyp_open nodes using an extension point (#625, @patricoferris)

• Add Ast_builder and Ast_pattern utilities to manipulate encoded
  effect patterns (#624, @NathanReb)

• Fix a bug where ppat_effects would be encoded/decoded instead of copied by
  the 5.4 <-> 5.3 migrations (#624, @NathanReb)

• Fix infinite loop when duplicate attributes are present, raising
  an error instead (#613, @ceastlund, @patricoferris)

• Ignore extensions inside attributes for the unused extension check
  (#616, @Skepfyr)

• Fix a bug that inserted Location.none into Longidents when using OCaml
  5.4 and above (#619, @patricoferris)

• Add support for OCaml 5.4 labeled tuples, they can now be used alongside
  ppx-es. Also adds Ast_builder and Ast_pattern utilities to manipulate them.
  (#607, @NathanReb)

CHANGES:

5.4 Support

• Add initial OCaml 5.4 support (#570, @patricoferris, @NathanReb)

Other Changes

• Add Longident.to/of_compiler to astlib to simplify maintenance
  of ppx-es that interacts with other parts of the compiler-libs such
  as the type checker. (#603, @NathanReb)

• Fix a bug where some infix operators such as mod would be printed as
  raw identifiers by our Pprintast. (#601, @NathanReb)

• Fix 5.2 -> 5.3 migration of constants. Those used to always have a none
  location which can lead to unhelpful error messages.
  (#569, @NathanReb)

• Add a new context-free rule type that replaces AST nodes that have the registered
  attributes attached to them. (#574, @Skepfyr)

• Allow users to derive code from module bindings and module declarations
  (#576, @patricoferris)

• Expose Ppxlib.Location.Error.t = Astlib.Location.Error.t (#593, @ceastlund)

• Add @@@ppxlib.inline.end, deprecate @@@deriving.end. (#594, @ceastlund)

• Clean the AST of any ppxlib migration attributes whenever printing using
  Pretty_print mode and the use_compiler_pp flag. (#598, @patricoferris)

• Add custom printer support to pp_ast functions via the ?printer config
  parameter. (#526, @pedrobslisboa)

CHANGES:

• Make Ast_builder's default value_binding constructor generate the proper
  pvb_constraint from the pattern and expression arguments.
  (#589, @NathanReb)
• Fix pprintast to output correct syntax from Ppat_constraint (pat, Ptyp_poly ...)
  nodes until they are completely dropped. (#588, @NathanReb)

CHANGES:

• Fix ppxlib driver's AST to source printer. Our copy of pprintast was not
  properly updated which resulted in incorrect printing of value bindings'
  constraints (#585, @NathanReb)

CHANGES:

• Change Location.none to match the compiler's Location.none as of OCaml
  4.08. This fixes a bug in loc_of_attribute (#540, @ncik-roberts, @patricoferris)

• Bump ppxlib's AST to 5.2.0 (#514, @patricoferris)

• Add the [@@@expand_inline] transformation and support for floating attribute context
  free transformations. (#560, @jaymody)

• Add a -raise-embedded-errors flag to the driver. Setting this flag raises the first
  ocaml.error embedded in the final AST.

• Export Ast_pattern.fail. (#563, @ceastlund)

• Make Ast_traverse.sexp_of more concise, and add a test. (#561, @ceastlund)

CHANGES:

• Allow use of effect syntax in preprocessed files without causing migration
  failures. (#552, @hhugo, @NathanReb)

• Remove support for compilers older than 4.08 (#556, @NathanReb)

• Add a --use-compiler-pp flag to the standalone driver. This flag
  can be set when the driver outputs source code to make it use the compiler's
  Pprintast instead of ppxlib's.
  (#555, @NathanReb)

CHANGES:

5.3 support

• Add initial OCaml 5.3 support (#487, @NathanReb, @hhugo, @nojb)

• Initialise OCaml 5.3's lexer with the keywords setting from OCAMLPARAM or
  the new -keywords driver's CLI option to allow the standalone ppx driver to
  process old packages using effect as an identifier
  (#535, @dra27, @NathanReb)

Other changes

• Add Pprintast.binding, longident and payload (#542, @mattiasdrp)

• Fix deriving_inline round-trip check so that it works with 5.01 <-> 5.02
  migrations (#519, @NathanReb)

• Add ppxlib's AST pretty-printing utilities in Ppxlib.Pp_ast and
  a ppxlib-pp-ast executable in a new separate ppxlib-tools package
  (#517, #525, #537, @NathanReb)

• Change -dparsetree from a sexp output to a pretty printed AST, closer
  to what the compiler's -dparsetree is.
  (#530, @NathanReb)

• Add Parsetree documentation comments to Ast_builder functions (#518, @patricoferris)

• Support class type declarations in derivers with the new, optional arguments
  {str,sig}_class_type_decl in Deriving.add (#538, @patricoferris)

CHANGES:

• Fix a bug where Code_path.main_module_name would not properly remove
  extensions from the filename and therefore return an invalid module name.
  (#512, @NathanReb)

• Add -unused-type-warnings flag to the driver to allow users to disable
  only the generation of warning 34 silencing structure items when using
  [@@deriving ...] on type declarations. (#511, @mbarbin, @NathanReb)

• Make -unused-code-warnings flag to the driver also controls the generation
  of warning 34 silencing structure items when using [@@deriving ...] on type
  declarations. (#510, @mbarbin, @NathanReb)

• Driver: Add -unused-code-warnings=force command-line flag argument. (#490, @mbarbin)

• new functions Ast_builder.{e,p}list_tail that take an extra tail
  expression/pattern argument parameter compared to Ast_builder.{e,p}list, so
  they can build ASTs like a :: b :: c instead of only [ a; b ].
  (#498, #502, @v-gb, @NathanReb)

• Fix Longident.parse so it also handles indexing operators such as
  .!(), .%(;..)<-, or Vec.(.%()) (#494, @Octachron)

• Add a special_function' variant which directly takes a Longident.t
  argument to avoid the issue that Longident.t cover distinct syntaxic classes
  which cannot be easily parsed by a common parser (#496, @Octachron).

• Keep location ranges consistent when migrating Pexp_function nodes from 5.2+
  to older versions (#504, @jchavarri)

• Fix -locations-check behaviour so it is no longer required to pass -check
  as well to enable location checks. (#506, @NathanReb)

CHANGES:

• Add support for OCaml 5.2

• Insert errors from caught located exceptions in place of the code that
  should have been generated by context-free rules. (#472, @NathanReb)

CHANGES:

• Add an optional embed_errors argument to Context_free.map_top_down that
  controls how to deal with exceptions thrown by context-free rules.
  (#468, @NathanReb)

• Fix Longident.parse so it properly handles unparenthesized dotted operators
  such as +. or *.. (#111, @rgrinberg, @NathanReb)

• raising an exception does no longer cancel the whole context free phase(#453, @Burnleydev1)

• Sort embedded errors that are appended to the AST by location so the compiler
  reports the one closer to the beginning of the file first. (#463, @NathanReb)

• Update Attribute.get to ignore loc_ghost. (#460, @ceastlund)

• Add API to manipulate attributes that are used as flags (#408, @dianaoigo)

• Update changelog to use ISO 8061 date format: YYYY-MM-DD. (#445, @ceastlund)

• Replace Caml with Stdlib. (#427, @ceastlund)

• When a transformation raises, the last valid AST is used as input to the upcoming
  transformations. All such errors are collected and appended as
  extension nodes to the final AST (#447, @Burnleydev1)

• Fix a small mistake in the man pages: Embededding errors is done by default with
  -as-pp, not with -dump-ast (#464, @pitag-ha)

• Set appropriate binary mode when writing to stdout especially for Windows
  compatibility. (#466, @jonahbeckford)