rescript

10.0.0

Compiler

:boom: Breaking Change

• bsconfig.json does not support // line comments anymore.
  • Example: "suffix": ".bs.js" // determine the suffix
  • Fix: remove the comment and use standard json.
• Changed return type of Js.String.match_ as it was wrong. #5070
  • Example: any use of Js.String.match_ and Js.String2.match_
  • Fix: follow the type errors
• GenType is now vendored in the compiler and drops support for the Flow and untyped back-ends to focus on providing a better experience for TypeScript.
  • Fix: keep on using the older version of the compiler and the separate genType package if Flow support is required. Migrate to TS if one wants to upgrade the compiler version.

:rocket: New Feature

• New records with optional fields e.g. type opt = {x: int, y?: string} were added as an experimental feature #5423 #5452 New Syntax
• Add support for @new @variadic (see https://github.com/rescript-lang/rescript-compiler/pull/5364)

:bug: Bug Fix

• Classify bigint correctly #5351
• Fixed crash in rescript build on Windows #5516
• Fixed rescript init command not working #5526
• Fix issue with compiler log not terminated that causes problems with editor extension not clearing issues when fixed #5545

:nail_care: Polish

• Changed Linux build to depend on GLIBC 2.28 again for compatibility with Debian 10.

• Proper M1 support (CI now supports M1 native builds)

Syntax

:boom: Breaking Change

• @bs.send.pipe is now removed. Earlier it was deprecated.
• Missing labels in function application is now an error (https://forum.rescript-lang.org/t/ann-more-strict-checks-in-missed-labels/2117).
  • Example: let f = (x, ~z) => x + z; f(1, 2)
  • Fix: do let f = (x, ~z) => x + z; f(1, ~z=2) instead
• Externals without @val annotations do not work anymore, and externals with = "" give an error.
  • Example: external setTimeout: (unit => unit, int) => float = "setTimeout" is not supported anymore.
  • Fix: use @val external setTimeout: (unit => unit, int) => float = "setTimeout" instead.
  • Example2: @val external setTimeout: (unit => unit, int) => float = "" is not supported anymore.
  • Fix2: use @val external setTimeout: (unit => unit, int) => float = "setTimeout" instead.
• Strings processed at compile-time don't need escaping anymore.
  • Example: let blockCommentsRe = %re("/\\/\\*([^*]|[\\r\\n]|(\\*+([^*/]|[\\r\\n])))*\\*+\\//g").
  • Fix: use let blockCommentsRe = %re("/\/\*([^*]|[\r\n]|(\*+([^*/]|[\r\n])))*\*+\//g") instead.
• Remove parsing of "import" and "export" which was never officially supported https://github.com/rescript-lang/syntax/pull/597 https://github.com/rescript-lang/syntax/pull/599
  • Example: export type t = int
  • Fix: @genType type t = int
  • Example2: import realValue: complexNumber => float from "./MyMath"
  • Fix2: @genType.import("./MyMath") external realValue: complexNumber => float = "realValue"

:rocket: New Feature

• Unicode is now supported in regular strings and chars (when the symbol fits). This is now going to work: let str = "Σ". And, you'll be able to pattern match on unicode chars: switch c { | 'Σ' => "what a fine unicode char" | _ => "unicode is fun" }
• Doc comments /** ... */ are now supported. Inernally, they are attributes, so are only valid at positions where @foo is allowed, or a syntax error is given. Similarly for module-level /*** comments */ that can go where @@attributes go.

:bug: Bug Fix

• Fix printing for inline nullary functor types #477
• Fix stripping of quotes for empty poly variants #474
• Implement syntax for arity zero vs arity one in uncurried application in #139
• Fix parsing of first class module exprs as part of binary/ternary expr in #256
• Fix formatter hanging on deeply nested function calls #261

Libraries

:boom: Breaking Change

• "Attributes not allowed here". If you see this error chances are you're using a ppx that needs updating to a new version. See an exampe of how to update a ppx
  • Example: for rescript-relay 0.23.0 is not supported.
  • Fix: use rescript-relay@beta or the new version when released.
• Removed printing modules (Printf, Format etc) and related functions. Details of files added/removed: https://github.com/rescript-lang/rescript-compiler/commit/0fd8bb0e77c4b0e96a9647ac8af614305057003f.

:bug: Bug Fix

• Fix library issue with missing bytes_to_string https://github.com/rescript-lang/rescript-compiler/issues/5573 https://github.com/rescript-lang/rescript-compiler/pull/5589

:nail_care: Polish

• Several Belt / Js libraries are now converted to ReScript syntax, with corresponding comments in Markdown format suitable for hovering. See #5361.

Playground

:house: Internal

• Added jsoo_playground_main.ml as the rescript-lang.org playground bundle entrypoint

:boom: Breaking Change

• Removed Reason syntax support for the playground experience. See https://github.com/rescript-lang/rescript-compiler/pull/5375