12.0.0-alpha.15

💥 Breaking Change

• New rewatch based build system. #7551 #7593
  • The new rewatch based build system is now the default and is exposed through the rescript command. The rewatch command has been removed.
  • The previous Ninja-based build system is now available via the rescript legacy subcommand.
  • Argument --compiler-args is now a subcommand compiler-args.
• Remove String.getSymbol, String.getSymbolUnsafe, String.setSymbol from standard library. #7571

🐛 Bug fix

• Ignore inferred arity in functions inside %raw functions, leaving to %ffi the responsibility to check the arity since it gives an error in case of mismatch. #7542
• Pass the rewatch exit code through in wrapper script. #7565
• Prop punning when types don't match results in I/O error: _none_: No such file or directory. #7533
• Pass location to children prop in jsx ppx. #7540
• Fix crash when -bs-g is used with untagged variants. #7575
• Fix issue with preserve mode where jsx is declared as an external without a @module attribute. #7591
• Rewatch: don't add deps to modules that are in packages that are not a dependency. #7612
• Rewatch: fix non-unicode stderr. #7613
• Fix rewatch considering warning configs of non-local dependencies. #7614
• Rewatch: fix panic if package.json name different from module name. #7616
• Fix finding the standard library for pnpm. #7615

💅 Polish

• Better error message for when trying to await something that is not a promise. #7561
• Better error messages for object field missing and object field type mismatches. #7580
• Better error messages for when polymorphic variants does not match for various reasons. #7596
• Improved completions for inline records. #7601
• Add OrThrow aliases for Belt functions ending with Exn. #7581, #7590 The following aliases have been added:
  • Belt.Array.getOrThrow
  • Belt.Array.setOrThrow
  • Belt.Map.getOrThrow
  • Belt.MutableMap.getOrThrow
  • Belt.Set.getOrThrow
  • Belt.MutableSet.getOrThrow
  • Belt.List.getOrThrow
  • Belt.List.tailOrThrow
  • Belt.List.headOrThrow
  • Belt.MutableQueue.peekOrThrow
  • Belt.MutableQueue.popOrThrow
  • Belt.Option.getOrThrow
  • Belt.Result.getOrThrow

🏠 Internal

• Remove @return(undefined_to_opt) and %undefined_to_opt primitive. #7462
• Migrate rewatch to Rust 2024 edition. #7602

12.0.0-alpha.14

💥 Breaking Change

• Iterator.forEach now emits Iterator.prototype.forEach call. #7506
• Rename functions ending with Exn to end with OrThrow. The old Exn functions are now deprecated:
  • Bool.fromStringExn → Bool.fromStringOrThrow
  • BigInt.fromStringExn → BigInt.fromStringOrThrow
  • JSON.parseExn → JSON.parseOrThrow
  • Changed BigInt.fromFloat to return an option rather than throwing an error.
  • Added BigInt.fromFloatOrThrow
  • Option.getExn → Option.getOrThrow
  • Null.getExn → Null.getOrThrow
  • Nullable.getExn → Nullable.getOrThrow
  • Result.getExn → Result.getOrThrow
  • List.getExn → List.getOrThrow
  • List.tailExn → List.tailOrThrow
  • List.headExn → List.headOrThrow
  • Old functions remain available but are marked as deprecated with guidance to use the new OrThrow variants.
  • #7518, #7554

🚀 New Feature

• Add RegExp.flags. #7461
• Add Array.findLast, Array.findLastWithIndex, Array.findLastIndex, Array.findLastIndexWithIndex and Array.findLastIndexOpt. #7503
• Add options argument to Console.dir. #7504
• Show variant constructor's inline record types on hover. #7519
• Add additional Iterator.prototype bindings to runtime/Stdlib_Iterator.res. #7506

🐛 Bug fix

• rescript-tools doc no longer includes shadowed bindings in its output. #7497
• Treat throw like raise in analysis. #7521
• Fix index out of bounds exception thrown in rare cases by rescript-editor-analysis.exe codeAction command. #7523
• Don't produce duplicate type definitions for recursive types on hover. #7524
• Prop punning when types don't match results in I/O error: _none_: No such file or directory. #7533
• Fix partial application with user-defined function types. #7548
• Fix doc comment before variant throwing syntax error. #7535
• Fix apparent non-determinism in generated code for pattern matching. #7557

💅 Polish

• Suggest awaiting promise before using it when types mismatch. #7498
• Complete from RegExp stdlib module for regexes. #7425
• Allow oneliner formatting when including module with single type alias. #7502
• Improve error messages for JSX type mismatches, passing objects where record is expected, passing array literal where tuple is expected, and more. #7500
• Show in error messages when coercion can be used to fix a type mismatch. #7505
• Remove deprecated pipe last (|>) syntax. #7512
• Improve error message for pipe (->) syntax. #7520
• Improve a few error messages around various subtyping issues. #7404
• In module declarations, accept the invalid syntax M = {...} and format it to M : {...}. #7527
• Improve doc comment formatting to match the style of multiline comments. #7529
• Improve error messages around type mismatches for try/catch, if, for, while, and optional record fields + optional function arguments. #7522
• Sync reanalyze with the new APIs around exception. #7536
• Improve array pattern spread error message. #7549
• Sync API docs with rescript-lang.org on release. #7555

🏠 Internal

• Refactor the ast for record expressions and patterns. #7528
• Editor: add completions from included modules. #7515
• Add -editor-mode arg to bsc for doing special optimizations only relevant to the editor tooling. #7541

12.0.0-alpha.13

💥 Breaking Change

• Rename JsError to JsExn and error modules cleanup. #7408
• Make BigInt.fromFloat return an option rather than throwing an error in case it's passed a value with a decimal value. #7419

🚀 New Feature

• Add shift (<<, >>, >>>) operators for int and bigint. #7183
• Add bitwise AND (&) operator for int and bigint. #7415
• Add bitwise NOT (~) operator for int and bigint. #7418
• Significantly reduced the download size by splitting binaries into optional platform-specific dependencies (e.g, @rescript/linux-x64). #7395
• JSX: do not error on ref as prop anymore (which is allowed in React 19). #7420
• Add new attribute @notUndefined for abstract types to prevent unnecessary wrapping with Primitive_option.some in JS output. #7458
• Preserve JSX: enable by adding "-bs-jsx-preserve" to "bsc-flags" (does require "jsx": { "version": 4 }). #7387
• Add slot prop to JsxDOM.domProps. #7487

🐛 Bug fix

• Fix broken bstracing CLI location. #7398
• Fix field flattening optimization to avoid creating unnecessary copies of allocating constants. #7421
• Fix leading comments removed when braces inside JSX contains let assignment. #7424
• Fix JSON escaping in code editor analysis: JSON was not always escaped properly, which prevented code actions from being available in certain situations. #7435
• Fix regression in pattern matching for optional fields containing variants. #7440
• Fix missing checks for duplicate literals in variants with payloads. #7441
• Fix printer removing private for empty record. #7448
• Fix: handle dynamic imports with module aliases. #7452
• Fix missing unescaping when accessing prop with exotic name. #7469
• Fix syntax error with mutable nested record. #7470

🏠 Internal

• AST: Add bar location to case. #7407
• Clean up lazy from ASTs and back-end. #7474
• Compile runtime with rewatch and add rewatch tests to the compiler repo. #7422

💅 Polish

• In type errors, recommend stdlib over Belt functions for converting between float/int/string. #7453
• Remove unused type Jsx.ref. #7459
• Add @notUndefined attribute to all relevant abstract types in Stdlib. #7464
• Editor: Add pipe completions from current module. #7471

12.0.0-alpha.12

🐛 Bug fix

• Fix node.js ExperimentalWarning. #7379
• Fix issue with gentype and stdlib json. #7378
• Fix type of RegExp.Result.matches. #7393
• Add optional flags argument to RegExp.fromString and deprecate RegExp.fromStringWithFlags. #7393

🏠 Internal

• Better representation of JSX in AST. #7286

💅 Polish

• Improve error message for missing value when the identifier is also the name of a module in scope. #7384
• Upgrade Flow parser to 0.267.0. #7390

12.0.0-alpha.11

🐛 Bug fix

• Fix Error.fromException. #7364
• Fix signature of throw. #7365
• Fix formatter adds superfluous parens in pipe chain. #7370

🏠 Internal

• Remove Stdlib_Char module for now. #7367
• Convert internal JavaScript codebase into ESM, ReScript package itself is now ESM ("type": "module"). #6899

💅 Polish

• More deprecations in Pervasives; add Stdlib.Pair and Stdlib.Int.Ref. #7371

12.0.0-alpha.10

🚀 New Feature

• Add Dict.has and double Dict.forEachWithKey/Dict.mapValues performance. #7316
• Add popover attributes to JsxDOM.domProps. #7317
• Add Array.removeInPlace helper based on splice. #7321
• Add inert attribute to JsxDOM.domProps. #7326
• Make reanalyze exception tracking work with the new stdlib. #7328
• Fix Pervasive.max using boolean comparison for floats. #7333
• Experimental: Support nested/inline record types - records defined inside of other records, without needing explicit separate type definitions. #7241
• Add unified exponentiation (**) operator for numeric types using ES7 **. #7153
• Rename raise to throw to align with JavaScript vocabulary. raise has been deprecated. #7346
• Add unified bitwise (^) operator. #7216
• Stdlib: rename binary operations to match JavaScript terms. #7353

💥 Breaking Change

• Replace ~date with ~day in Date.make. #7324
• Remove -bs-jsx-mode. #7327
• Drop Node.js version <20 support, as it is reaching End-of-Life. #7354
• Treat int multiplication as a normal int32 operation instead of using Math.imul. #7358

🏠 Internal

• Clean up legacy tags handling. #7309
• Use Yarn (Berry) workspaces for internal tooling. #7309

💅 Polish

• Deprecate JSON.Classify.classify. #7315
• Hide stdlib modules in output. #7305
• Deprecate unsafe host-specific bindings from stdlib. #7334
• Make unsafe function names consistent in Stdlib.String. #7337
• rescript package does not trigger postinstall script anymore. #7350
• Add Stdlib Bool and Char modules and improve Pervasives deprecation messages. #7361

🐛 Bug fix

• Fix recursive untagged variant type checking by delaying well-formedness checks until environment construction completes. #7320
• Fix incorrect expansion of polymorphic return types in uncurried function applications. #7338

11.2.0-beta.2

🏠 Internal

• Playground: use TLS 1.2 to upload files to CDN using FTP. #7307

12.0.0-alpha.9

💥 Breaking Change

• Clean list API. #7290

💅 Polish

• Allow single newline in JSX. #7269
• Editor: Always complete from Core first. Use actual native regex syntax in code snippets for regexps. #7295
• Add type t to Stdlib modules. #7302
• Gentype: handle null/nullable/undefined from Stdlib. #7132

🐛 Bug fix

• Fix async context checking for module await. #7271
• Fix %external extension. #7272
• Fix issue with type environment for unified ops. #7277
• Fix completion for application with tagged template. #7278
• Fix error message for arity in the presence of optional arguments. #7284
• Fix issue in functors with more than one argument (which are curried): emit nested function always. #7273
• Fix dot completion issue with React primitives. #7292
• Stdlib namespace for Core modules (fixes name clashes with user modules). #7285
• Fix runtime type check for Object in untagged variants when one variant case is null. #7303
• Fix files that were being truncated when sent to the CDN over FTP. #7306
• Fix better editor completion for applications. #7291
• Fix @react.componentWithProps no longer works with @directive("'use memo'"). #7300

🏠 Internal

• Remove ignore in res_scanner.ml. #7280
• Use the new stdlib modules in the analysis tests. #7295
• Build with OCaml 5.3.0. #7294
• Simplify JSON.Decode implementation. #7304

11.2.0-beta.1

💥 Breaking Change

• Deprecate JSX 3. #7042
• Deprecate js_cast.res. #7074
• Deprecate top-level "suffix" option in rescript.json. #7056

🐛 Bug Fix

• Handle absolute file paths in gentype. #7111
• Fix "rescript format" with many files. #7081
• Fix exponential notation syntax. #7174
• Fix formatter handling of wildcard in pattern matching records with no fields specified. #7224

🏠 Internal

• Playground: Bundle and upload stdlib runtime so that the playground can execute functions from Core/Belt/Js. #7268

12.0.0-alpha.8

🐛 Bug fix

• Editor: Fix issue where pipe completions would not trigger with generic type arguments. #7231
• Fix leftover assert false in code for null != undefined. #7232
• Editor: Fix issue where completions would not show up inside of object bodies. #7230
• Fix issue with pattern matching empty list which interferes with boolean optimisations. #7237
• Fix Cannot combine @react.component and @directive. #7260
• Fix issue where attributes on an application were not preserved by the AST conversion for ppx. #7262

🏠 Internal

• AST cleanup: Prepare for ast async cleanup: Refactor code for @res.async payload handling and clean up handling of type and term parameters, so that now each => in a function definition corresponds to a function. #7223
• AST: always put type parameters first in function definitions. #7233
• AST cleanup: Remove @res.async attribute from the internal representation, and add a flag to untyped and typed ASTs instead. #7234
• AST cleanup: Remove unused expression_desc.Pexp_new, expression_desc.Pexp_setinstvar, expression_desc.Pexp_override, expression_desc.Pexp_poly, exp_extra.Texp_poly, expression_desc.Texp_new, expression_desc.Texp_setinstvar, expression_desc.Texp_override & expression_desc.Texp_instvar from AST. #7239
• AST cleanup: Remove @res.partial attribute from the internal representation, and add a flag to untyped and typed ASTs instead. #7238 #7240
• AST cleanup: Remove unused structure_item_desc.Pstr_class, signature_item_desc.Psig_class, structure_item_desc.Pstr_class_type, signature_item_desc.Psig_class_type, structure_item_desc.Tstr_class, structure_item_desc.Tstr_class_type, signature_item_desc.Tsig_class, signature_item_desc.Tsig_class_type from AST. #7242
• AST cleanup: remove |. and rename |. to -> in the internal representation for the pipe operator. #7244
• AST cleanup: represent concatenation (++) and (dis)equality operators (==, ===, !=, !==) just like in the syntax. #7248
• AST cleanup: use inline record for Ptyp_arrow. #7250
• Playground: Bundle stdlib runtime so that the playground can execute functions from Core/Belt/Js. #7255
• AST cleanup: Remove res.namedArgLoc attribute and store the location information directly into the label. #7247