CHANGELOG.md

Changelog

changelog should follow Keep a Changelog conventions.

MoonBit Language Changes no need for such detailed classification.

[0.8.1]

moonbitlang/core Changes

Added

• Core commit: bd827dc85
• Added Debug trait with derive(Debug) support, including ignore=[..] configuration for non-debuggable nested types
• Added new moonbitlang/async APIs including @process.spawn, advisory file locking, @fs.tmpdir, @async.all, and @async.any
• Added Array::release_unused(placeholder~), which overwrites the unused capacity of an array in place with a placeholder, releasing the elements that earlier removals left there
• Added Deque::release_unused(placeholder~), which overwrites the unused capacity of a deque in place with a placeholder, releasing the elements that earlier removals left there

Changed

• Array shrinking operations no longer null out the slots they vacate, so an ArrayView created before the mutation can no longer read uninitialized memory (previously a segfault on native and null on wasm-gc; the JavaScript backend is unchanged, and such a view still observes undefined past the array's current length there). Mutating an array while a view of it is alive remains a program error, but it now yields unspecified valid values rather than undefined behavior. The removed elements stay reachable from the buffer until later pushes reuse those slots, the buffer grows, or the array is dropped -- uniformly, clear included, which no longer releases them. Array::release_unused(placeholder~) overwrites the unused capacity in place with a placeholder to release them on demand, while shrink_to_fit, which already reallocated, lets them go with the old buffer. No existing signature changes
• Deque shrinking operations no longer null out the slots they vacate, so an ArrayView obtained from Deque::as_views before the mutation can no longer read uninitialized memory (previously a segfault on native, null/undefined elsewhere). Mutating a deque while a view of it is alive remains a program error, but it now yields unspecified valid values rather than undefined behavior. The removed elements stay reachable from the buffer until later pushes reuse those slots, the buffer grows, or the deque is dropped -- uniformly, clear included, which no longer releases them. Deque::release_unused(placeholder~) overwrites the unused capacity in place with a placeholder to release them on demand, while shrink_to_fit, which already reallocated, lets them go with the old buffer. No existing signature changes
• BREAKING: @json.parse now rejects unpaired \uXXXX surrogate escapes in strings, raising ParseError::InvalidChar at the backslash that opens the offending escape; an escaped leading surrogate must be followed immediately by an escaped trailing surrogate, and the pair decodes to the character it denotes. Previously such escapes were decoded unchecked and produced a String that was not well-formed Unicode. @json.valid reports the same documents as invalid. JSON emitted by JSON.stringify in JavaScript can contain these escapes, so input that JavaScript and Python accept may now be rejected — as it is by Rust's serde_json
• @json.inspect has been migrated to json_inspect
• String::sub and StringView::sub now panic on invalid indices instead of raising CreatingViewError. The CreatingViewError type has been removed.

Removed

• BREAKING: Removed the immut/array package, whose entire API was deprecated. Use immut/vector instead.

MoonBit Language Changes

Added

• Added declare keyword (replacing #declaration_only) for staged declarations, including declared impl relationships
• Added reversed-range syntax x>..y / x>=..y for for .. in
• Added user-defined struct constructors (fn new + S::new)
• Added panic backtrace support on wasm-gc/native/LLVM backends in debug mode
• Added moon fetch, moon ide hover, and moon ide rename subcommands
• Added moon test -j, moon test --outline, and range form of moon test --index

Changed

• for/while/for .. in loop else blocks are now written with nobreak
• x..f() semantics are standardized as { x.f(); x }, and ignored-return misuse now warns
• moon -C <path> now changes working directory semantics; --manifest-path was added
• moon run and moon build now default to --debug
• .mbt.md dependency front matter supports package-level imports and aliasing

Deprecated

• Deprecated suberror Err PayloadType in favor of enum-like suberror syntax
• Deprecated x..=y in favor of x..<=y for closed forward ranges
• Deprecated effect inference for local fn that performs raise/async without explicit annotation
• Deprecated moon.pkg.json in favor of moon.pkg
• Deprecated old moon install behavior (installing project dependencies)

[0.7.1]

moonbitlang/core Changes

Added

• Core commit: c0b22a8b0
• moonbitlang/async now supports Windows (MSVC), plus updates to @fs.mkdir (recursive) and process APIs
• Experimental lexmatch now supports POSIX character classes like [:digit:]

MoonBit Language Changes

Added

• Added warning for unused async
• Optional argument default expressions can now raise (when function signature allows it)
• Added #declaration_only for staged/spec-driven declarations
• Added pipeline shorthand e1 |> x => e2
• Added loop invariants/reasoning annotations for for loops
• Added experimental moon.pkg support (migration via NEW_MOON_PKG=1 moon fmt)
• Added moon ide subcommands (peek-def, outline, doc) and doc-test mbt check support

Changed

• SourceLoc output now uses relative paths
• moon add now runs moon update automatically
• New moon backend is enabled by default (NEW_MOON=0 to switch back)
• Build artifacts moved from target to _build (with a target symlink for compatibility)
• Iter in moonbitlang/core migrated to external iterator semantics (single-pass traversal)

Deprecated

• Inferring Ref through struct literal { val: ... } is deprecated
• Iterator alias and .iterator() methods are deprecated in favor of Iter and .iter()

[0.6.36]

moonbitlang/core Changes

Added

• Export FromJson trait from @json package in prelude for easier JSON deserialization

Changed

• BREAKING: String::at and StringView::at now return UInt16 instead of Int and are the primary methods for accessing UTF-16 code units
• BREAKING: String::code_unit_at and StringView::code_unit_at are now aliases for at instead of being separate methods
• String::trim, String::trim_start, String::trim_end and their StringView counterparts now accept optional chars parameter with default whitespace characters

Deprecated

• String::charcode_at (previously named at) is now deprecated, use String::at which returns UInt16
• String::trim_space and StringView::trim_space are now deprecated, use trim() with default whitespace characters instead

Removed

Fixed

MoonBit Language Changes

Added

• Introduced the #declaration_only attribute for function, method, and type declarations. These declarations can be called or tested immediately but require a concrete implementation to function at runtime. Accessing a declaration without an implementation will result in a runtime crash.

• The compiler can now report unused warning on async annotations when the function is actually synchronous

• moonfmt will automatically migrate mbt test/mbt test(async) code blocks in Markdown to mbt check.

Changed

• The default value of optional arguments can now raise error or perform async operations, as long as the function itself allow these effects

• Refactored the representation of JS backend trait objects. Each trait object now consists of two fields: the underlying data and a method table. This allows trait objects of the same type to share a single method table.

Deprecated

[0.6.35]

moonbitlang/core Changes

Added

• String::fold String::rev_fold StringView::fold StringView::rev_fold now supports error polymorphism (#3034)

• ArrayView::get is added (#3025)

Changed

• The output format of SourceLoc has been changed (#3035)

Deprecated

• Result::or Result::or_else are deprecated in favor of Result::unwrap_or Result::unwrap_or_else (#3031)
• Passing max_nesting_depth to @json.parse is deprecated. (#3028)

MoonBit Language Changes

Added

• #module attribute now supports importing JS modules in CJS format

• Docstrings now support mbt check to mark MoonBit code blocks that participate in compilation. Currently, mbt check blocks in docstrings have the following restrictions:

  1. Only test code is allowed in mbt check blocks
  2. mbt check blocks must not contain parse errors

Changed

• An array literal without a type annotation that is bound to a local variable is now inferred as Array; if the variable is only read, or only read and written, the user is prompted to annotate it as ReadOnlyArray or FixedArray

Deprecated

• We will remove the previously added mbt test and mbt test(async) support in the future, keeping only mbt check

[0.6.33]

moonbitlang/core Changes

Added

• Core commit: b989ba000
• Added MutArrayView as the unified mutable slice type
• Added #module("...") support for importing third-party JS modules

Changed

• ArrayView is now the unified immutable slice for Array/FixedArray/ReadOnlyArray
• string[x] now returns UInt16 (migrate to code_unit_at)

Deprecated

• Deprecated Container::of in favor of Type::from_array(ArrayView[_])
• Renamed @test.T to @test.Test and @priority_queue.T to @priorityqueue.PriorityQueue

MoonBit Language Changes

Added

• ReadOnlyArray now supports pattern matching, slicing, and spread
• Bitstring patterns now support signed extraction
• Added #label_migration for parameter-label alias/deprecation migration
• Added warning mnemonics and #warnings local configuration
• Added test_unqualified_package warning (disabled by default)
• Added mbt test and mbt test(async) markdown/doc code blocks

Changed

• Cascade calls now allow non-Unit intermediate returns with invalid_cascade warning
• mbt/moonbit code blocks no longer type-check by default; use mbt check
• Default behavior changed for #deprecated: now warns in current package unless skip_current_package=true
• Experimental lexmatch now supports first mode with search/non-greedy behavior
• Alerts are merged into warning configuration

[0.6.30]

moonbitlang/core Changes

Added

• Core commit: 07d9d2445
• Added external iterator type support (Iterator) with for .. in integration via .iterator()/.iterator2()

MoonBit Language Changes

Added

• Added using @pkg { ... } as unified alias syntax for values, types, and traits
• Added #alias support for types and traits
• Added duplicate test-name warnings
• Added experimental lexmatch? and case-insensitive regex modifier (?i:...)
• Added ReadOnlyArray built-in type for immutable fixed-length lookup tables
• Added anti-pattern lint warnings for selected patterns
• Added #deprecated(skip_current_package=...) parameter

Changed

• Bitstring patterns now require explicit endianness suffixes such as u1be and u32le

Deprecated

• traitalias, fnalias, and typealias are being migrated toward using, type Alias = ..., and #alias
• Deprecated moon info --no-alias

[0.6.29]

moonbitlang/core Changes

Added

• Core commit: 9037370fc
• Added per-process randomized hashing to mitigate HashDoS risks

Changed

• ArrayView became immutable

MoonBit Language Changes

Added

• Added async test and async fn main (native backend on Linux/macOS)
• Added experimental lexmatch expression for StringView/BytesView
• Added unified using imports with pub using support for re-export
• Added optional parameters on trait methods
• Added #alias operator-overloading aliases for methods like get/set/view
• Released wasm toolchain packages for x86 Darwin and ARM Linux
• Added .mbt.md formatting support in moon fmt

Removed

• Removed long-deprecated behavior where fn meth(self : T, ..) could also be called as a plain function
• Removed direct_use from moon.pkg.json (replaced by using)