gopherjs · nevkontakte · Jun 30, 2024 · Jun 3, 2024
diff --git a/compiler/expressions.go b/compiler/expressions.go
@@ -201,7 +201,7 @@ func (fc *funcContext) translateExpr(expr ast.Expr) *expression {
 		}
 
 	case *ast.FuncLit:
-		_, fun := translateFunction(e.Type, nil, e.Body, fc, exprType.(*types.Signature), fc.pkgCtx.FuncLitInfos[e], "", typeparams.Instance{})
+		fun := fc.nestedFunctionContext(fc.pkgCtx.FuncLitInfos[e], exprType.(*types.Signature), typeparams.Instance{}).translateFunctionBody(e.Type, nil, e.Body, "")
 		if len(fc.pkgCtx.escapingVars) != 0 {
 			names := make([]string, 0, len(fc.pkgCtx.escapingVars))
 			for obj := range fc.pkgCtx.escapingVars {

diff --git a/compiler/functions.go b/compiler/functions.go
@@ -0,0 +1,320 @@
+package compiler
+
+// functions.go contains logic responsible for translating top-level functions
+// and function literals.
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/types"
+	"sort"
+	"strings"
+
+	"github.com/gopherjs/gopherjs/compiler/analysis"
+	"github.com/gopherjs/gopherjs/compiler/astutil"
+	"github.com/gopherjs/gopherjs/compiler/internal/typeparams"
+	"github.com/gopherjs/gopherjs/compiler/typesutil"
+)
+
+// newFunctionContext creates a new nested context for a function corresponding
+// to the provided info and instance.
+func (fc *funcContext) nestedFunctionContext(info *analysis.FuncInfo, sig *types.Signature, inst typeparams.Instance) *funcContext {
+	if info == nil {
+		panic(fmt.Errorf("missing *analysis.FuncInfo"))
+	}
+	if sig == nil {
+		panic(fmt.Errorf("missing *types.Signature"))
+	}
+
+	c := &funcContext{
+		FuncInfo:     info,
+		pkgCtx:       fc.pkgCtx,
+		parent:       fc,
+		allVars:      make(map[string]int, len(fc.allVars)),
+		localVars:    []string{},
+		flowDatas:    map[*types.Label]*flowData{nil: {}},
+		caseCounter:  1,
+		labelCases:   make(map[*types.Label]int),
+		typeResolver: fc.typeResolver,
+		objectNames:  map[types.Object]string{},
+		sig:          &typesutil.Signature{Sig: sig},
+	}
+	for k, v := range fc.allVars {
+		c.allVars[k] = v
+	}
+
+	if sig.TypeParams().Len() > 0 {
+		c.typeResolver = typeparams.NewResolver(c.pkgCtx.typesCtx, typeparams.ToSlice(sig.TypeParams()), inst.TArgs)
+	} else if sig.RecvTypeParams().Len() > 0 {
+		c.typeResolver = typeparams.NewResolver(c.pkgCtx.typesCtx, typeparams.ToSlice(sig.RecvTypeParams()), inst.TArgs)
+	}
+	if c.objectNames == nil {
+		c.objectNames = map[types.Object]string{}
+	}
+
+	return c
+}
+
+// translateTopLevelFunction translates a top-level function declaration
+// (standalone function or method) into a corresponding JS function.
+//
+// Returns a string with a JavaScript statements that define the function or
+// method. For methods it returns declarations for both value- and
+// pointer-receiver (if appropriate).
+func (fc *funcContext) translateTopLevelFunction(fun *ast.FuncDecl, inst typeparams.Instance) []byte {
+	if fun.Recv == nil {
+		return fc.translateStandaloneFunction(fun, inst)
+	}
+
+	o := inst.Object.(*types.Func)
+	info := fc.pkgCtx.FuncDeclInfos[o]
+
+	sig := o.Type().(*types.Signature)
+	// primaryFunction generates a JS function equivalent of the current Go function
+	// and assigns it to the JS expression defined by lvalue.
+	primaryFunction := func(lvalue string) []byte {
+		if fun.Body == nil {
+			return []byte(fmt.Sprintf("\t%s = function() {\n\t\t$throwRuntimeError(\"native function not implemented: %s\");\n\t};\n", lvalue, o.FullName()))
+		}
+
+		var recv *ast.Ident
+		if fun.Recv != nil && fun.Recv.List[0].Names != nil {
+			recv = fun.Recv.List[0].Names[0]
+		}
+		fun := fc.nestedFunctionContext(info, sig, inst).translateFunctionBody(fun.Type, recv, fun.Body, lvalue)
+		return []byte(fmt.Sprintf("\t%s = %s;\n", lvalue, fun))
+	}
+
+	funName := fun.Name.Name
+	if reservedKeywords[funName] {
+		funName += "$"
+	}
+
+	// proxyFunction generates a JS function that forwards the call to the actual
+	// method implementation for the alternate receiver (e.g. pointer vs
+	// non-pointer).
+	proxyFunction := func(lvalue, receiver string) []byte {
+		fun := fmt.Sprintf("function(...$args) { return %s.%s(...$args); }", receiver, funName)
+		return []byte(fmt.Sprintf("\t%s = %s;\n", lvalue, fun))
+	}
+
+	recvInst := inst.Recv()
+	recvInstName := fc.instName(recvInst)
+	recvType := recvInst.Object.Type().(*types.Named)
+
+	// Objects the method should be assigned to for the plain and pointer type
+	// of the receiver.
+	prototypeVar := fmt.Sprintf("%s.prototype.%s", recvInstName, funName)
+	ptrPrototypeVar := fmt.Sprintf("$ptrType(%s).prototype.%s", recvInstName, funName)
+
+	code := bytes.NewBuffer(nil)
+
+	if _, isStruct := recvType.Underlying().(*types.Struct); isStruct {
+		// Structs are a special case: they are represented by JS objects and their
+		// methods are the underlying object's methods. Due to reference semantics
+		// of the JS variables, the actual backing object is considered to represent
+		// the pointer-to-struct type, and methods are attacher to it first and
+		// foremost.
+		code.Write(primaryFunction(ptrPrototypeVar))
+		code.Write(proxyFunction(prototypeVar, "this.$val"))
+		return code.Bytes()
+	}
+
+	if ptr, isPointer := sig.Recv().Type().(*types.Pointer); isPointer {
+		if _, isArray := ptr.Elem().Underlying().(*types.Array); isArray {
+			// Pointer-to-array is another special case.
+			// TODO(nevkontakte) Find out and document why.
+			code.Write(primaryFunction(prototypeVar))
+			code.Write(proxyFunction(ptrPrototypeVar, fmt.Sprintf("(new %s(this.$get()))", recvInstName)))
+			return code.Bytes()
+		}
+
+		// Methods with pointer-receiver are only attached to the pointer-receiver
+		// type.
+		return primaryFunction(ptrPrototypeVar)
+	}
+
+	// Methods defined for non-pointer receiver are attached to both pointer- and
+	// non-pointer-receiver types.
+	recvExpr := "this.$get()"
+	if isWrapped(recvType) {
+		recvExpr = fmt.Sprintf("new %s(%s)", recvInstName, recvExpr)
+	}
+	code.Write(primaryFunction(prototypeVar))
+	code.Write(proxyFunction(ptrPrototypeVar, recvExpr))
+	return code.Bytes()
+}
+
+// translateStandaloneFunction translates a package-level function.
+//
+// It returns a JS statements which define the corresponding function in a
+// package context. Exported functions are also assigned to the `$pkg` object.
+func (fc *funcContext) translateStandaloneFunction(fun *ast.FuncDecl, inst typeparams.Instance) []byte {
+	o := inst.Object.(*types.Func)
+	info := fc.pkgCtx.FuncDeclInfos[o]
+	sig := o.Type().(*types.Signature)
+
+	if fun.Recv != nil {
+		panic(fmt.Errorf("expected standalone function, got method: %s", o))
+	}
+
+	lvalue := fc.instName(inst)
+
+	if fun.Body == nil {
+		return []byte(fmt.Sprintf("\t%s = function() {\n\t\t$throwRuntimeError(\"native function not implemented: %s\");\n\t};\n", lvalue, o.FullName()))
+	}
+
+	body := fc.nestedFunctionContext(info, sig, inst).translateFunctionBody(fun.Type, nil, fun.Body, lvalue)
+	code := bytes.NewBuffer(nil)
+	fmt.Fprintf(code, "\t%s = %s;\n", lvalue, body)
+	if fun.Name.IsExported() {
+		fmt.Fprintf(code, "\t$pkg.%s = %s;\n", encodeIdent(fun.Name.Name), lvalue)
+	}
+	return code.Bytes()
+}
+
+// translateFunctionBody translates body of a top-level or literal function.
+//
+// It returns a JS function expression that represents the given Go function.
+// Function receiver must have been created with nestedFunctionContext() to have
+// required metadata set up.
+func (fc *funcContext) translateFunctionBody(typ *ast.FuncType, recv *ast.Ident, body *ast.BlockStmt, funcRef string) string {
+	prevEV := fc.pkgCtx.escapingVars
+
+	// Generate a list of function argument variables. Since Go allows nameless
+	// arguments, we have to generate synthetic names for their JS counterparts.
+	var args []string
+	for _, param := range typ.Params.List {
+		if len(param.Names) == 0 {
+			args = append(args, fc.newLocalVariable("param"))
+			continue
+		}
+		for _, ident := range param.Names {
+			if isBlank(ident) {
+				args = append(args, fc.newLocalVariable("param"))
+				continue
+			}
+			args = append(args, fc.objectName(fc.pkgCtx.Defs[ident]))
+		}
+	}
+
+	bodyOutput := string(fc.CatchOutput(1, func() {
+		if len(fc.Blocking) != 0 {
+			fc.pkgCtx.Scopes[body] = fc.pkgCtx.Scopes[typ]
+			fc.handleEscapingVars(body)
+		}
+
+		if fc.sig != nil && fc.sig.HasNamedResults() {
+			fc.resultNames = make([]ast.Expr, fc.sig.Sig.Results().Len())
+			for i := 0; i < fc.sig.Sig.Results().Len(); i++ {
+				result := fc.sig.Sig.Results().At(i)
+				typ := fc.typeResolver.Substitute(result.Type())
+				fc.Printf("%s = %s;", fc.objectName(result), fc.translateExpr(fc.zeroValue(typ)).String())
+				id := ast.NewIdent("")
+				fc.pkgCtx.Uses[id] = result
+				fc.resultNames[i] = fc.setType(id, typ)
+			}
+		}
+
+		if recv != nil && !isBlank(recv) {
+			this := "this"
+			if isWrapped(fc.typeOf(recv)) {
+				this = "this.$val" // Unwrap receiver value.
+			}
+			fc.Printf("%s = %s;", fc.translateExpr(recv), this)
+		}
+
+		fc.translateStmtList(body.List)
+		if len(fc.Flattened) != 0 && !astutil.EndsWithReturn(body.List) {
+			fc.translateStmt(&ast.ReturnStmt{}, nil)
+		}
+	}))
+
+	sort.Strings(fc.localVars)
+
+	var prefix, suffix, functionName string
+
+	if len(fc.Flattened) != 0 {
+		// $s contains an index of the switch case a blocking function reached
+		// before getting blocked. When execution resumes, it will allow to continue
+		// from where we left off.
+		fc.localVars = append(fc.localVars, "$s")
+		prefix = prefix + " $s = $s || 0;"
+	}
+
+	if fc.HasDefer {
+		fc.localVars = append(fc.localVars, "$deferred")
+		suffix = " }" + suffix
+		if len(fc.Blocking) != 0 {
+			suffix = " }" + suffix
+		}
+	}
+
+	localVarDefs := "" // Function-local var declaration at the top.
+
+	if len(fc.Blocking) != 0 {
+		if funcRef == "" {
+			funcRef = "$b"
+			functionName = " $b"
+		}
+
+		localVars := append([]string{}, fc.localVars...)
+		// There are several special variables involved in handling blocking functions:
+		// $r is sometimes used as a temporary variable to store blocking call result.
+		// $c indicates that a function is being resumed after a blocking call when set to true.
+		// $f is an object used to save and restore function context for blocking calls.
+		localVars = append(localVars, "$r")
+		// If a blocking function is being resumed, initialize local variables from the saved context.
+		localVarDefs = fmt.Sprintf("var {%s, $c} = $restore(this, {%s});\n", strings.Join(localVars, ", "), strings.Join(args, ", "))
+		// If the function gets blocked, save local variables for future.
+		saveContext := fmt.Sprintf("var $f = {$blk: "+funcRef+", $c: true, $r, %s};", strings.Join(fc.localVars, ", "))
+
+		suffix = " " + saveContext + "return $f;" + suffix
+	} else if len(fc.localVars) > 0 {
+		// Non-blocking functions simply declare local variables with no need for restore support.
+		localVarDefs = fmt.Sprintf("var %s;\n", strings.Join(fc.localVars, ", "))
+	}
+
+	if fc.HasDefer {
+		prefix = prefix + " var $err = null; try {"
+		deferSuffix := " } catch(err) { $err = err;"
+		if len(fc.Blocking) != 0 {
+			deferSuffix += " $s = -1;"
+		}
+		if fc.resultNames == nil && fc.sig.HasResults() {
+			deferSuffix += fmt.Sprintf(" return%s;", fc.translateResults(nil))
+		}
+		deferSuffix += " } finally { $callDeferred($deferred, $err);"
+		if fc.resultNames != nil {
+			deferSuffix += fmt.Sprintf(" if (!$curGoroutine.asleep) { return %s; }", fc.translateResults(fc.resultNames))
+		}
+		if len(fc.Blocking) != 0 {
+			deferSuffix += " if($curGoroutine.asleep) {"
+		}
+		suffix = deferSuffix + suffix
+	}
+
+	if len(fc.Flattened) != 0 {
+		prefix = prefix + " s: while (true) { switch ($s) { case 0:"
+		suffix = " } return; }" + suffix
+	}
+
+	if fc.HasDefer {
+		prefix = prefix + " $deferred = []; $curGoroutine.deferStack.push($deferred);"
+	}
+
+	if prefix != "" {
+		bodyOutput = fc.Indentation(1) + "/* */" + prefix + "\n" + bodyOutput
+	}
+	if suffix != "" {
+		bodyOutput = bodyOutput + fc.Indentation(1) + "/* */" + suffix + "\n"
+	}
+	if localVarDefs != "" {
+		bodyOutput = fc.Indentation(1) + localVarDefs + bodyOutput
+	}
+
+	fc.pkgCtx.escapingVars = prevEV
+
+	return fmt.Sprintf("function%s(%s) {\n%s%s}", functionName, strings.Join(args, ", "), bodyOutput, fc.Indentation(0))
+}