internal/cm: update to go.bytecodealliance.org/cm@v0.2.0

src/internal/cm/CHANGELOG.md

@@ -0,0 +1,23 @@
+# Changelog
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [v0.2.0] — 2025-03-15
+
+### Added
+
+- Initial support for Component Model [async](https://github.com/WebAssembly/component-model/blob/main/design/mvp/Async.md) types `stream`, `future`, and `error-context`.
+- Initial support for JSON serialization of WIT `list`, `enum`, and `record` types.
+- Added `cm.CaseUnmarshaler` helper for text and JSON unmarshaling of `enum` and `variant` types.
+
+### Changed
+
+- Breaking: package `cm`: removed `bool` from `Discriminant` type constraint. It was not used by code generation.
+
+## [v0.1.0] — 2024-12-14
+
+Initial version, extracted into module [`go.bytecodealliance.org/cm`](https://pkg.go.dev/go.bytecodealliance.org/cm).
+
+[Unreleased]: <https://github.com/bytecodealliance/go-modules/compare/cm/v0.2.0..HEAD>
+[v0.2.0]: <https://github.com/bytecodealliance/go-modules/compare/cm/v0.1.0..cm/v0.2.0>
+[v0.1.0]: <https://github.com/bytecodealliance/go-modules/tree/cm/v0.1.0>

src/internal/cm/LICENSE

@@ -0,0 +1,220 @@
+
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src/internal/cm/README.md

@@ -0,0 +1,15 @@
+# go.bytecodealliance.org/cm
+
+[![pkg.go.dev](https://img.shields.io/badge/docs-pkg.go.dev-blue.svg)](https://pkg.go.dev/go.bytecodealliance.org/cm) [![build status](https://img.shields.io/github/actions/workflow/status/bytecodealliance/go-modules/test.yaml?branch=main)](https://github.com/bytecodealliance/go-modules/actions)
+
+## About
+
+Package `cm` contains helper types and functions used by generated packages, such as `option<t>`, `result<ok, err>`, `variant`, `list`, and `resource`. These are intended for use by generated [Component Model](https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md#type-definitions) bindings, where the caller converts to a Go equivalent. It attempts to map WIT semantics to their equivalent in Go where possible.
+
+### Note on Memory Safety
+
+Package `cm` and generated bindings from `wit-bindgen-go` may have compatibility issues with the Go garbage collector, as they directly represent `variant` and `result` types as tagged unions where a pointer shape may be occupied by a non-pointer value. The GC may detect and throw an error if it detects a non-pointer value in an area it expects to see a pointer. This is an area of active development.
+
+## License
+
+This project is licensed under the Apache 2.0 license with the LLVM exception. See [LICENSE](../LICENSE) for more details.

src/internal/cm/RELEASE.md

@@ -0,0 +1,34 @@
+# Release
+
+This document describes the steps to release a new version of module `go.bytecodealliance.org/cm`.
+
+## 1. Update [CHANGELOG.md](./CHANGELOG.md)
+
+1. Add the latest changes to [CHANGELOG.md](./CHANGELOG.md).
+1. Rename the Unreleased section to reflect the new version number.
+	1. Update the links to new version tag in the footer of CHANGELOG.md
+1. Add today’s date (YYYY-MM-DD) after an em dash (—).
+1. Submit a [GitHub Pull Request](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests) with these updates.
+
+## 2. Create a new release
+
+Once the PR is merged, tag the new version in Git and push the tag to GitHub.
+
+**Note:** the tag **must** start with the prefix `cm/` in order to correctly tag this module.
+
+For example, to tag version `cm/v0.2.0`:
+
+```console
+git tag cm/v0.2.0
+git push origin cm/v0.2.0
+```
+
+## 3. Update the root module
+
+Once the tag is pushed, you can update the root module to depend on the newly created version of package `cm` by running the following:
+
+```console
+go get -u go.bytecodealliance.org/cm@latest
+```
+
+Then follow the instructions in [RELEASE.md](../RELEASE.md) to release a new version of the root module.

src/internal/cm/case.go

@@ -0,0 +1,51 @@
+package cm
+
+import "errors"
+
+// CaseUnmarshaler returns an function that can unmarshal text into
+// [variant] or [enum] case T.
+//
+// [enum]: https://component-model.bytecodealliance.org/design/wit.html#enums
+// [variant]: https://component-model.bytecodealliance.org/design/wit.html#variants
+func CaseUnmarshaler[T ~uint8 | ~uint16 | ~uint32](cases []string) func(v *T, text []byte) error {
+	if len(cases) <= linearScanThreshold {
+		return func(v *T, text []byte) error {
+			if len(text) == 0 {
+				return errEmpty
+			}
+			s := string(text)
+			for i := 0; i < len(cases); i++ {
+				if cases[i] == s {
+					*v = T(i)
+					return nil
+				}
+			}
+			return errNoMatchingCase
+		}
+	}
+
+	m := make(map[string]T, len(cases))
+	for i, v := range cases {
+		m[v] = T(i)
+	}
+
+	return func(v *T, text []byte) error {
+		if len(text) == 0 {
+			return errEmpty
+		}
+		s := string(text)
+		c, ok := m[s]
+		if !ok {
+			return errNoMatchingCase
+		}
+		*v = c
+		return nil
+	}
+}
+
+const linearScanThreshold = 16
+
+var (
+	errEmpty          = errors.New("empty text")
+	errNoMatchingCase = errors.New("no matching case")
+)

src/internal/cm/docs.go

@@ -1,4 +1,4 @@
-// Package cm contains types and functions for interfacing with the WebAssembly Component Model.
+// Package cm provides types and functions for interfacing with the WebAssembly Component Model.
 //
 // The types in this package (such as [List], [Option], [Result], and [Variant]) are designed to match the memory layout
 // of [Component Model] types as specified in the [Canonical ABI].

src/internal/cm/empty.s

@@ -0,0 +1,3 @@
+// This file exists for testing this package without WebAssembly,
+// allowing empty function bodies with a //go:wasmimport directive.
+// See https://pkg.go.dev/cmd/compile for more information.

src/internal/cm/error.go

@@ -0,0 +1,40 @@
+package cm
+
+import "unsafe"
+
+// ErrorContext represents the Component Model [error-context] type,
+// an immutable, non-deterministic, host-defined value meant to aid in debugging.
+//
+// [error-context]: https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md#error-context-type
+type ErrorContext struct {
+	_ HostLayout
+	errorContext
+}
+
+type errorContext uint32
+
+// Error implements the [error] interface. It returns the debug message associated with err.
+func (err errorContext) Error() string {
+	return err.DebugMessage()
+}
+
+// String implements [fmt.Stringer].
+func (err errorContext) String() string {
+	return err.DebugMessage()
+}
+
+// DebugMessage represents the Canonical ABI [error-context.debug-message] function.
+//
+// [error-context.debug-message]: https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md#error-contextdebug-message
+func (err errorContext) DebugMessage() string {
+	var s string
+	wasmimport_errorContextDebugMessage(err, unsafe.Pointer(&s))
+	return s
+}
+
+// Drop represents the Canonical ABI [error-context.drop] function.
+//
+// [error-context.drop]: https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md#error-contextdrop
+func (err errorContext) Drop() {
+	wasmimport_errorContextDrop(err)
+}

src/internal/cm/error.wasm.go

@@ -0,0 +1,13 @@
+package cm
+
+import "unsafe"
+
+// msg uses unsafe.Pointer for compatibility with go1.23 and lower.
+//
+//go:wasmimport canon error-context.debug-message
+//go:noescape
+func wasmimport_errorContextDebugMessage(err errorContext, msg unsafe.Pointer)
+
+//go:wasmimport canon error-context.drop
+//go:noescape
+func wasmimport_errorContextDrop(err errorContext)

src/internal/cm/future.go

@@ -0,0 +1,15 @@
+package cm
+
+// Future represents the Component Model [future] type.
+// A future is a special case of stream. In non-error cases,
+// a future delivers exactly one value before being automatically closed.
+//
+// [future]: https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md#asynchronous-value-types
+type Future[T any] struct {
+	_ HostLayout
+	future[T]
+}
+
+type future[T any] uint32
+
+// TODO: implement methods on type future

src/internal/cm/go.mod

@@ -0,0 +1,3 @@
+module go.bytecodealliance.org/cm
+
+go 1.23.0

src/internal/cm/list.go

@@ -1,6 +1,10 @@
 package cm
 
-import "unsafe"
+import (
+	"bytes"
+	"encoding/json"
+	"unsafe"
+)
 
 // List represents a Component Model list.
 // The binary representation of list<T> is similar to a Go slice minus the cap field.
@@ -58,3 +62,57 @@ func (l list[T]) Data() *T {
 func (l list[T]) Len() uintptr {
 	return l.len
 }
+
+// MarshalJSON implements json.Marshaler.
+func (l list[T]) MarshalJSON() ([]byte, error) {
+	if l.len == 0 {
+		return []byte("[]"), nil
+	}
+
+	s := l.Slice()
+	var zero T
+	if unsafe.Sizeof(zero) == 1 {
+		// The default Go json.Encoder will marshal []byte as base64.
+		// We override that behavior so all int types have the same serialization format.
+		// []uint8{1,2,3} -> [1,2,3]
+		// []uint32{1,2,3} -> [1,2,3]
+		return json.Marshal(sliceOf(s))
+	}
+	return json.Marshal(s)
+}
+
+type slice[T any] []entry[T]
+
+func sliceOf[S ~[]E, E any](s S) slice[E] {
+	return *(*slice[E])(unsafe.Pointer(&s))
+}
+
+type entry[T any] [1]T
+
+func (v entry[T]) MarshalJSON() ([]byte, error) {
+	return json.Marshal(v[0])
+}
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (l *list[T]) UnmarshalJSON(data []byte) error {
+	if bytes.Equal(data, nullLiteral) {
+		return nil
+	}
+
+	var s []T
+	err := json.Unmarshal(data, &s)
+	if err != nil {
+		return err
+	}
+
+	l.data = unsafe.SliceData([]T(s))
+	l.len = uintptr(len(s))
+
+	return nil
+}
+
+// nullLiteral is the JSON representation of a null literal.
+// By convention, to approximate the behavior of Unmarshal itself,
+// Unmarshalers implement UnmarshalJSON([]byte("null")) as a no-op.
+// See https://pkg.go.dev/encoding/json#Unmarshaler for more information.
+var nullLiteral = []byte("null")

src/internal/cm/stream.go

@@ -0,0 +1,15 @@
+package cm
+
+// Stream represents the Component Model [stream] type.
+// A stream is a special case of stream. In non-error cases,
+// a stream delivers exactly one value before being automatically closed.
+//
+// [stream]: https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md#asynchronous-value-types
+type Stream[T any] struct {
+	_ HostLayout
+	stream[T]
+}
+
+type stream[T any] uint32
+
+// TODO: implement methods on type stream

src/internal/cm/variant.go

@@ -3,10 +3,9 @@ package cm
 import "unsafe"
 
 // Discriminant is the set of types that can represent the tag or discriminator of a variant.
-// Use bool for 2-case variant types, result<T>, or option<T> types, uint8 where there are 256 or
+// Use uint8 where there are 256 or fewer cases, uint16 for up to 65,536 cases, or uint32 for anything greater.
-// fewer cases, uint16 for up to 65,536 cases, or uint32 for anything greater.
 type Discriminant interface {
-	bool | uint8 | uint16 | uint32
+	uint8 | uint16 | uint32
 }
 
 // Variant represents a loosely-typed Component Model variant.