bindgen, internal/go, wit: WIP

Generating valid Go names from WIT names:
1. Scan for an explicit mapping, e.g. wasi:clocks/wall-clock -> wasi/clocks/wallclock
2. Perform string conversion, e.g. : -> /, strip -
3. (optional) validate short package name as valid Go identifier
4. Check against list of Go reserved words
5. For decl names, convert to Go-style names (TitleCase), check against existing decl

bindgen/bindgen.go

@@ -5,7 +5,9 @@ package bindgen
 
 import (
 	"fmt"
+	"strings"
 
+	"github.com/ydnar/wasm-tools-go/internal/codec"
 	"github.com/ydnar/wasm-tools-go/internal/go/gen"
 	"github.com/ydnar/wasm-tools-go/wit"
 )
@@ -15,35 +17,78 @@ const HeaderPattern = `// Code generated by %s. DO NOT EDIT.`
 // Go generates one or more Go packages from [wit.Resolve] res.
 // It returns any error that occurs during code generation.
 func Go(res *wit.Resolve, opts ...Option) ([]*gen.Package, error) {
-	var state genState
-	state.opts.apply(opts...)
-	state.res = res
+	g, err := newGenerator(res, opts...)
+	if err != nil {
+		return nil, err
+	}
 
 	// By default, each WIT interface and world maps to a single Go package.
 	// Options might override the Go package, including combining multiple
 	// WIT interfaces and/or worlds into a single Go package.
-	for _, w := range state.res.Worlds {
+	for _, w := range g.res.Worlds {
 		id := worldIdent(w)
 		fmt.Printf("%s → %s\n", id, id)
 	}
 
-	return state.finish()
+	return g.finish()
+}
+
+type generator struct {
+	opts       options
+	res        *wit.Resolve
+	packages   map[string]*gen.Package
+	packageMap map[wit.Ident]*gen.Package
 }
 
-type genState struct {
-	opts     options
-	res      *wit.Resolve
-	packages map[wit.Ident]*gen.Package
+func newGenerator(res *wit.Resolve, opts ...Option) (*generator, error) {
+	state := &generator{}
+	err := state.opts.apply(opts...)
+	if err != nil {
+		return nil, err
+	}
+	state.res = res
+	return state, nil
 }
 
-func (state *genState) finish() ([]*gen.Package, error) {
+func (g *generator) finish() ([]*gen.Package, error) {
 	var packages []*gen.Package
-	for _, pkg := range state.packages {
-		packages = append(packages, pkg)
+	for _, path := range codec.SortedKeys(g.packages) {
+		packages = append(packages, g.packages[path])
 	}
 	return packages, nil
 }
 
+func (g *generator) goPackageIdent(id wit.Ident) gen.Ident {
+	// Remove Name field, which doesn’t affect package path.
+	id = id.InterfaceIdent()
+
+	// Check existing Go packages first.
+	if pkg, ok := g.packageMap[id]; ok {
+		return pkg.Ident
+	}
+
+	// Check ident mappings.
+	if gid, ok := g.opts.idents[id]; ok {
+		return gid
+	}
+	var base string
+	if gid, ok := g.opts.idents[id.PackageIdent()]; ok {
+		base = gid.Path
+	} else {
+		base = strings.ReplaceAll(id.Package, ":", "/")
+	}
+
+	// Concatenate
+	if id.Interface != "" {
+		return gen.Ident{
+			// TODO: strip '-' characters
+			Path: base + "/" + id.Interface,
+		}
+	}
+
+	return gen.Ident{Path: base}
+}
+
 func worldIdent(w *wit.World) wit.Ident {
 	var id wit.Ident
 	id.Package = w.Package.Name.ShortString()

bindgen/options.go

@@ -1,14 +1,19 @@
 package bindgen
 
+import (
+	"github.com/ydnar/wasm-tools-go/internal/go/gen"
+	"github.com/ydnar/wasm-tools-go/wit"
+)
+
 // Option represents a single configuration option for this package.
 type Option interface {
-	applyOption(*options)
+	applyOption(*options) error
 }
 
-type optionFunc func(*options)
+type optionFunc func(*options) error
 
-func (f optionFunc) applyOption(opts *options) {
-	f(opts)
+func (f optionFunc) applyOption(opts *options) error {
+	return f(opts)
 }
 
 type options struct {
@@ -21,20 +26,25 @@ type options struct {
 	// "wasi:clocks/wall-clock" -> "wasi/clocks/wall#wallclock" (for a Go short package name of wallclock)
 	// "wasi:clocks/wall-clock.datetime" -> "wasi/clocks/wall#DateTime"
 	// "wasi:clocks/wall-clock.now" -> "wasi/clocks/wall#Now"
-	idents map[string]string
+	idents map[wit.Ident]gen.Ident
 }
 
-func (opts *options) apply(o ...Option) {
+func (opts *options) apply(o ...Option) error {
 	for _, o := range o {
-		o.applyOption(opts)
+		err := o.applyOption(opts)
+		if err != nil {
+			return err
+		}
 	}
+	return nil
 }
 
 // GeneratedBy returns an [Option] that specifies the name of the program or package
 // that will appear in the "Code generated by ..." header on generated files.
 func GeneratedBy(name string) Option {
-	return optionFunc(func(opts *options) {
+	return optionFunc(func(opts *options) error {
 		opts.generator = name
+		return nil
 	})
 }
 
@@ -50,11 +60,20 @@ func GeneratedBy(name string) Option {
 //
 // [WIT]: https://github.com/WebAssembly/component-model/blob/main/design/mvp/WIT.md
 func MapIdent(from, to string) Option {
-	return optionFunc(func(opts *options) {
+	return optionFunc(func(opts *options) error {
 		if opts.idents == nil {
-			opts.idents = make(map[string]string)
+			opts.idents = make(map[wit.Ident]gen.Ident)
+		}
+		fromIdent, err := wit.ParseIdent(from)
+		if err != nil {
+			return err
 		}
-		opts.idents[from] = to
+		toIdent, err := gen.ParseIdent(to)
+		if err != nil {
+			return err
+		}
+		opts.idents[fromIdent] = toIdent
+		return nil
 	})
 }
 
@@ -63,12 +82,13 @@ func MapIdent(from, to string) Option {
 //
 // [WIT]: https://github.com/WebAssembly/component-model/blob/main/design/mvp/WIT.md
 func MapIdents(idents map[string]string) Option {
-	return optionFunc(func(opts *options) {
-		if opts.idents == nil {
-			opts.idents = make(map[string]string, len(idents))
-		}
+	return optionFunc(func(opts *options) error {
 		for from, to := range idents {
-			opts.idents[from] = to
+			err := MapIdent(from, to).applyOption(opts)
+			if err != nil {
+				return err
+			}
 		}
+		return nil
 	})
 }

internal/go/gen/gen.go

@@ -11,11 +11,8 @@ import (
 // Package represents a Go package, containing zero or more files
 // of generated code, along with zero or more declarations.
 type Package struct {
-	// Path is the Go package path, e.g. "encoding/json"
-	Path string
-
-	// Name is the short Go package name, e.g. "json"
-	Name string
+	// Ident is the package path and name.
+	Ident
 
 	// Files is the list of Go source files in this package.
 	Files map[string]*File

internal/go/gen/gen_test.go

@@ -9,8 +9,10 @@ func TestFileString(t *testing.T) {
 	f := &File{
 		Build: "wasm || wasm32 || tinygo.wasm",
 		Package: &Package{
-			Path: "wasm/wasi/clocks/wallclock",
-			Name: "wallclock",
+			Ident: Ident{
+				Path: "wasm/wasi/clocks/wallclock",
+				Name: "wallclock",
+			},
 		},
 		Imports: map[string]string{
 			"encoding/json": "json",

wit/ident.go

@@ -28,6 +28,29 @@ func ParseIdent(s string) (Ident, error) {
 	return id, err
 }
 
+// PackageIdent returns the package-only Ident for id.
+// For example, "wasi:clocks/wall-clock.DateTime" returns "wasi:clocks".
+func (id Ident) PackageIdent() Ident {
+	return Ident{
+		Package: id.Package,
+	}
+}
+
+// InterfaceIdent returns the interface-only Ident for id.
+// For example, "wasi:clocks/wall-clock.DateTime" returns "wasi:clocks/wall-clock".
+func (id Ident) InterfaceIdent() Ident {
+	return Ident{
+		Package:   id.Package,
+		Interface: id.Interface,
+	}
+}
+
+// WorldIdent returns the world-only Ident for id.
+// For example, "wasi:clocks/imports.DateTime" returns "wasi:clocks/imports".
+func (id Ident) WorldIdent() Ident {
+	return id.InterfaceIdent()
+}
+
 // String returns the canonical string representation of id. It implements the [fmt.Stringer] interface.
 //
 // The canonical string representation of an [Ident] is "$package[/$interface[.$name]]". Examples: