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-rw-r--r--src/text/template/exec.go1067
1 files changed, 1067 insertions, 0 deletions
diff --git a/src/text/template/exec.go b/src/text/template/exec.go
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--- /dev/null
+++ b/src/text/template/exec.go
@@ -0,0 +1,1067 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+ "errors"
+ "fmt"
+ "internal/fmtsort"
+ "io"
+ "reflect"
+ "runtime"
+ "strings"
+ "text/template/parse"
+)
+
+// maxExecDepth specifies the maximum stack depth of templates within
+// templates. This limit is only practically reached by accidentally
+// recursive template invocations. This limit allows us to return
+// an error instead of triggering a stack overflow.
+var maxExecDepth = initMaxExecDepth()
+
+func initMaxExecDepth() int {
+ if runtime.GOARCH == "wasm" {
+ return 1000
+ }
+ return 100000
+}
+
+// state represents the state of an execution. It's not part of the
+// template so that multiple executions of the same template
+// can execute in parallel.
+type state struct {
+ tmpl *Template
+ wr io.Writer
+ node parse.Node // current node, for errors
+ vars []variable // push-down stack of variable values.
+ depth int // the height of the stack of executing templates.
+}
+
+// variable holds the dynamic value of a variable such as $, $x etc.
+type variable struct {
+ name string
+ value reflect.Value
+}
+
+// push pushes a new variable on the stack.
+func (s *state) push(name string, value reflect.Value) {
+ s.vars = append(s.vars, variable{name, value})
+}
+
+// mark returns the length of the variable stack.
+func (s *state) mark() int {
+ return len(s.vars)
+}
+
+// pop pops the variable stack up to the mark.
+func (s *state) pop(mark int) {
+ s.vars = s.vars[0:mark]
+}
+
+// setVar overwrites the last declared variable with the given name.
+// Used by variable assignments.
+func (s *state) setVar(name string, value reflect.Value) {
+ for i := s.mark() - 1; i >= 0; i-- {
+ if s.vars[i].name == name {
+ s.vars[i].value = value
+ return
+ }
+ }
+ s.errorf("undefined variable: %s", name)
+}
+
+// setTopVar overwrites the top-nth variable on the stack. Used by range iterations.
+func (s *state) setTopVar(n int, value reflect.Value) {
+ s.vars[len(s.vars)-n].value = value
+}
+
+// varValue returns the value of the named variable.
+func (s *state) varValue(name string) reflect.Value {
+ for i := s.mark() - 1; i >= 0; i-- {
+ if s.vars[i].name == name {
+ return s.vars[i].value
+ }
+ }
+ s.errorf("undefined variable: %s", name)
+ return zero
+}
+
+var zero reflect.Value
+
+type missingValType struct{}
+
+var missingVal = reflect.ValueOf(missingValType{})
+
+var missingValReflectType = reflect.TypeOf(missingValType{})
+
+func isMissing(v reflect.Value) bool {
+ return v.IsValid() && v.Type() == missingValReflectType
+}
+
+// at marks the state to be on node n, for error reporting.
+func (s *state) at(node parse.Node) {
+ s.node = node
+}
+
+// doublePercent returns the string with %'s replaced by %%, if necessary,
+// so it can be used safely inside a Printf format string.
+func doublePercent(str string) string {
+ return strings.ReplaceAll(str, "%", "%%")
+}
+
+// TODO: It would be nice if ExecError was more broken down, but
+// the way ErrorContext embeds the template name makes the
+// processing too clumsy.
+
+// ExecError is the custom error type returned when Execute has an
+// error evaluating its template. (If a write error occurs, the actual
+// error is returned; it will not be of type ExecError.)
+type ExecError struct {
+ Name string // Name of template.
+ Err error // Pre-formatted error.
+}
+
+func (e ExecError) Error() string {
+ return e.Err.Error()
+}
+
+func (e ExecError) Unwrap() error {
+ return e.Err
+}
+
+// errorf records an ExecError and terminates processing.
+func (s *state) errorf(format string, args ...any) {
+ name := doublePercent(s.tmpl.Name())
+ if s.node == nil {
+ format = fmt.Sprintf("template: %s: %s", name, format)
+ } else {
+ location, context := s.tmpl.ErrorContext(s.node)
+ format = fmt.Sprintf("template: %s: executing %q at <%s>: %s", location, name, doublePercent(context), format)
+ }
+ panic(ExecError{
+ Name: s.tmpl.Name(),
+ Err: fmt.Errorf(format, args...),
+ })
+}
+
+// writeError is the wrapper type used internally when Execute has an
+// error writing to its output. We strip the wrapper in errRecover.
+// Note that this is not an implementation of error, so it cannot escape
+// from the package as an error value.
+type writeError struct {
+ Err error // Original error.
+}
+
+func (s *state) writeError(err error) {
+ panic(writeError{
+ Err: err,
+ })
+}
+
+// errRecover is the handler that turns panics into returns from the top
+// level of Parse.
+func errRecover(errp *error) {
+ e := recover()
+ if e != nil {
+ switch err := e.(type) {
+ case runtime.Error:
+ panic(e)
+ case writeError:
+ *errp = err.Err // Strip the wrapper.
+ case ExecError:
+ *errp = err // Keep the wrapper.
+ default:
+ panic(e)
+ }
+ }
+}
+
+// ExecuteTemplate applies the template associated with t that has the given name
+// to the specified data object and writes the output to wr.
+// If an error occurs executing the template or writing its output,
+// execution stops, but partial results may already have been written to
+// the output writer.
+// A template may be executed safely in parallel, although if parallel
+// executions share a Writer the output may be interleaved.
+func (t *Template) ExecuteTemplate(wr io.Writer, name string, data any) error {
+ tmpl := t.Lookup(name)
+ if tmpl == nil {
+ return fmt.Errorf("template: no template %q associated with template %q", name, t.name)
+ }
+ return tmpl.Execute(wr, data)
+}
+
+// Execute applies a parsed template to the specified data object,
+// and writes the output to wr.
+// If an error occurs executing the template or writing its output,
+// execution stops, but partial results may already have been written to
+// the output writer.
+// A template may be executed safely in parallel, although if parallel
+// executions share a Writer the output may be interleaved.
+//
+// If data is a reflect.Value, the template applies to the concrete
+// value that the reflect.Value holds, as in fmt.Print.
+func (t *Template) Execute(wr io.Writer, data any) error {
+ return t.execute(wr, data)
+}
+
+func (t *Template) execute(wr io.Writer, data any) (err error) {
+ defer errRecover(&err)
+ value, ok := data.(reflect.Value)
+ if !ok {
+ value = reflect.ValueOf(data)
+ }
+ state := &state{
+ tmpl: t,
+ wr: wr,
+ vars: []variable{{"$", value}},
+ }
+ if t.Tree == nil || t.Root == nil {
+ state.errorf("%q is an incomplete or empty template", t.Name())
+ }
+ state.walk(value, t.Root)
+ return
+}
+
+// DefinedTemplates returns a string listing the defined templates,
+// prefixed by the string "; defined templates are: ". If there are none,
+// it returns the empty string. For generating an error message here
+// and in html/template.
+func (t *Template) DefinedTemplates() string {
+ if t.common == nil {
+ return ""
+ }
+ var b strings.Builder
+ t.muTmpl.RLock()
+ defer t.muTmpl.RUnlock()
+ for name, tmpl := range t.tmpl {
+ if tmpl.Tree == nil || tmpl.Root == nil {
+ continue
+ }
+ if b.Len() == 0 {
+ b.WriteString("; defined templates are: ")
+ } else {
+ b.WriteString(", ")
+ }
+ fmt.Fprintf(&b, "%q", name)
+ }
+ return b.String()
+}
+
+// Sentinel errors for use with panic to signal early exits from range loops.
+var (
+ walkBreak = errors.New("break")
+ walkContinue = errors.New("continue")
+)
+
+// Walk functions step through the major pieces of the template structure,
+// generating output as they go.
+func (s *state) walk(dot reflect.Value, node parse.Node) {
+ s.at(node)
+ switch node := node.(type) {
+ case *parse.ActionNode:
+ // Do not pop variables so they persist until next end.
+ // Also, if the action declares variables, don't print the result.
+ val := s.evalPipeline(dot, node.Pipe)
+ if len(node.Pipe.Decl) == 0 {
+ s.printValue(node, val)
+ }
+ case *parse.BreakNode:
+ panic(walkBreak)
+ case *parse.CommentNode:
+ case *parse.ContinueNode:
+ panic(walkContinue)
+ case *parse.IfNode:
+ s.walkIfOrWith(parse.NodeIf, dot, node.Pipe, node.List, node.ElseList)
+ case *parse.ListNode:
+ for _, node := range node.Nodes {
+ s.walk(dot, node)
+ }
+ case *parse.RangeNode:
+ s.walkRange(dot, node)
+ case *parse.TemplateNode:
+ s.walkTemplate(dot, node)
+ case *parse.TextNode:
+ if _, err := s.wr.Write(node.Text); err != nil {
+ s.writeError(err)
+ }
+ case *parse.WithNode:
+ s.walkIfOrWith(parse.NodeWith, dot, node.Pipe, node.List, node.ElseList)
+ default:
+ s.errorf("unknown node: %s", node)
+ }
+}
+
+// walkIfOrWith walks an 'if' or 'with' node. The two control structures
+// are identical in behavior except that 'with' sets dot.
+func (s *state) walkIfOrWith(typ parse.NodeType, dot reflect.Value, pipe *parse.PipeNode, list, elseList *parse.ListNode) {
+ defer s.pop(s.mark())
+ val := s.evalPipeline(dot, pipe)
+ truth, ok := isTrue(indirectInterface(val))
+ if !ok {
+ s.errorf("if/with can't use %v", val)
+ }
+ if truth {
+ if typ == parse.NodeWith {
+ s.walk(val, list)
+ } else {
+ s.walk(dot, list)
+ }
+ } else if elseList != nil {
+ s.walk(dot, elseList)
+ }
+}
+
+// IsTrue reports whether the value is 'true', in the sense of not the zero of its type,
+// and whether the value has a meaningful truth value. This is the definition of
+// truth used by if and other such actions.
+func IsTrue(val any) (truth, ok bool) {
+ return isTrue(reflect.ValueOf(val))
+}
+
+func isTrue(val reflect.Value) (truth, ok bool) {
+ if !val.IsValid() {
+ // Something like var x interface{}, never set. It's a form of nil.
+ return false, true
+ }
+ switch val.Kind() {
+ case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+ truth = val.Len() > 0
+ case reflect.Bool:
+ truth = val.Bool()
+ case reflect.Complex64, reflect.Complex128:
+ truth = val.Complex() != 0
+ case reflect.Chan, reflect.Func, reflect.Pointer, reflect.Interface:
+ truth = !val.IsNil()
+ case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+ truth = val.Int() != 0
+ case reflect.Float32, reflect.Float64:
+ truth = val.Float() != 0
+ case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+ truth = val.Uint() != 0
+ case reflect.Struct:
+ truth = true // Struct values are always true.
+ default:
+ return
+ }
+ return truth, true
+}
+
+func (s *state) walkRange(dot reflect.Value, r *parse.RangeNode) {
+ s.at(r)
+ defer func() {
+ if r := recover(); r != nil && r != walkBreak {
+ panic(r)
+ }
+ }()
+ defer s.pop(s.mark())
+ val, _ := indirect(s.evalPipeline(dot, r.Pipe))
+ // mark top of stack before any variables in the body are pushed.
+ mark := s.mark()
+ oneIteration := func(index, elem reflect.Value) {
+ if len(r.Pipe.Decl) > 0 {
+ if r.Pipe.IsAssign {
+ // With two variables, index comes first.
+ // With one, we use the element.
+ if len(r.Pipe.Decl) > 1 {
+ s.setVar(r.Pipe.Decl[0].Ident[0], index)
+ } else {
+ s.setVar(r.Pipe.Decl[0].Ident[0], elem)
+ }
+ } else {
+ // Set top var (lexically the second if there
+ // are two) to the element.
+ s.setTopVar(1, elem)
+ }
+ }
+ if len(r.Pipe.Decl) > 1 {
+ if r.Pipe.IsAssign {
+ s.setVar(r.Pipe.Decl[1].Ident[0], elem)
+ } else {
+ // Set next var (lexically the first if there
+ // are two) to the index.
+ s.setTopVar(2, index)
+ }
+ }
+ defer s.pop(mark)
+ defer func() {
+ // Consume panic(walkContinue)
+ if r := recover(); r != nil && r != walkContinue {
+ panic(r)
+ }
+ }()
+ s.walk(elem, r.List)
+ }
+ switch val.Kind() {
+ case reflect.Array, reflect.Slice:
+ if val.Len() == 0 {
+ break
+ }
+ for i := 0; i < val.Len(); i++ {
+ oneIteration(reflect.ValueOf(i), val.Index(i))
+ }
+ return
+ case reflect.Map:
+ if val.Len() == 0 {
+ break
+ }
+ om := fmtsort.Sort(val)
+ for i, key := range om.Key {
+ oneIteration(key, om.Value[i])
+ }
+ return
+ case reflect.Chan:
+ if val.IsNil() {
+ break
+ }
+ if val.Type().ChanDir() == reflect.SendDir {
+ s.errorf("range over send-only channel %v", val)
+ break
+ }
+ i := 0
+ for ; ; i++ {
+ elem, ok := val.Recv()
+ if !ok {
+ break
+ }
+ oneIteration(reflect.ValueOf(i), elem)
+ }
+ if i == 0 {
+ break
+ }
+ return
+ case reflect.Invalid:
+ break // An invalid value is likely a nil map, etc. and acts like an empty map.
+ default:
+ s.errorf("range can't iterate over %v", val)
+ }
+ if r.ElseList != nil {
+ s.walk(dot, r.ElseList)
+ }
+}
+
+func (s *state) walkTemplate(dot reflect.Value, t *parse.TemplateNode) {
+ s.at(t)
+ tmpl := s.tmpl.Lookup(t.Name)
+ if tmpl == nil {
+ s.errorf("template %q not defined", t.Name)
+ }
+ if s.depth == maxExecDepth {
+ s.errorf("exceeded maximum template depth (%v)", maxExecDepth)
+ }
+ // Variables declared by the pipeline persist.
+ dot = s.evalPipeline(dot, t.Pipe)
+ newState := *s
+ newState.depth++
+ newState.tmpl = tmpl
+ // No dynamic scoping: template invocations inherit no variables.
+ newState.vars = []variable{{"$", dot}}
+ newState.walk(dot, tmpl.Root)
+}
+
+// Eval functions evaluate pipelines, commands, and their elements and extract
+// values from the data structure by examining fields, calling methods, and so on.
+// The printing of those values happens only through walk functions.
+
+// evalPipeline returns the value acquired by evaluating a pipeline. If the
+// pipeline has a variable declaration, the variable will be pushed on the
+// stack. Callers should therefore pop the stack after they are finished
+// executing commands depending on the pipeline value.
+func (s *state) evalPipeline(dot reflect.Value, pipe *parse.PipeNode) (value reflect.Value) {
+ if pipe == nil {
+ return
+ }
+ s.at(pipe)
+ value = missingVal
+ for _, cmd := range pipe.Cmds {
+ value = s.evalCommand(dot, cmd, value) // previous value is this one's final arg.
+ // If the object has type interface{}, dig down one level to the thing inside.
+ if value.Kind() == reflect.Interface && value.Type().NumMethod() == 0 {
+ value = reflect.ValueOf(value.Interface()) // lovely!
+ }
+ }
+ for _, variable := range pipe.Decl {
+ if pipe.IsAssign {
+ s.setVar(variable.Ident[0], value)
+ } else {
+ s.push(variable.Ident[0], value)
+ }
+ }
+ return value
+}
+
+func (s *state) notAFunction(args []parse.Node, final reflect.Value) {
+ if len(args) > 1 || !isMissing(final) {
+ s.errorf("can't give argument to non-function %s", args[0])
+ }
+}
+
+func (s *state) evalCommand(dot reflect.Value, cmd *parse.CommandNode, final reflect.Value) reflect.Value {
+ firstWord := cmd.Args[0]
+ switch n := firstWord.(type) {
+ case *parse.FieldNode:
+ return s.evalFieldNode(dot, n, cmd.Args, final)
+ case *parse.ChainNode:
+ return s.evalChainNode(dot, n, cmd.Args, final)
+ case *parse.IdentifierNode:
+ // Must be a function.
+ return s.evalFunction(dot, n, cmd, cmd.Args, final)
+ case *parse.PipeNode:
+ // Parenthesized pipeline. The arguments are all inside the pipeline; final must be absent.
+ s.notAFunction(cmd.Args, final)
+ return s.evalPipeline(dot, n)
+ case *parse.VariableNode:
+ return s.evalVariableNode(dot, n, cmd.Args, final)
+ }
+ s.at(firstWord)
+ s.notAFunction(cmd.Args, final)
+ switch word := firstWord.(type) {
+ case *parse.BoolNode:
+ return reflect.ValueOf(word.True)
+ case *parse.DotNode:
+ return dot
+ case *parse.NilNode:
+ s.errorf("nil is not a command")
+ case *parse.NumberNode:
+ return s.idealConstant(word)
+ case *parse.StringNode:
+ return reflect.ValueOf(word.Text)
+ }
+ s.errorf("can't evaluate command %q", firstWord)
+ panic("not reached")
+}
+
+// idealConstant is called to return the value of a number in a context where
+// we don't know the type. In that case, the syntax of the number tells us
+// its type, and we use Go rules to resolve. Note there is no such thing as
+// a uint ideal constant in this situation - the value must be of int type.
+func (s *state) idealConstant(constant *parse.NumberNode) reflect.Value {
+ // These are ideal constants but we don't know the type
+ // and we have no context. (If it was a method argument,
+ // we'd know what we need.) The syntax guides us to some extent.
+ s.at(constant)
+ switch {
+ case constant.IsComplex:
+ return reflect.ValueOf(constant.Complex128) // incontrovertible.
+
+ case constant.IsFloat &&
+ !isHexInt(constant.Text) && !isRuneInt(constant.Text) &&
+ strings.ContainsAny(constant.Text, ".eEpP"):
+ return reflect.ValueOf(constant.Float64)
+
+ case constant.IsInt:
+ n := int(constant.Int64)
+ if int64(n) != constant.Int64 {
+ s.errorf("%s overflows int", constant.Text)
+ }
+ return reflect.ValueOf(n)
+
+ case constant.IsUint:
+ s.errorf("%s overflows int", constant.Text)
+ }
+ return zero
+}
+
+func isRuneInt(s string) bool {
+ return len(s) > 0 && s[0] == '\''
+}
+
+func isHexInt(s string) bool {
+ return len(s) > 2 && s[0] == '0' && (s[1] == 'x' || s[1] == 'X') && !strings.ContainsAny(s, "pP")
+}
+
+func (s *state) evalFieldNode(dot reflect.Value, field *parse.FieldNode, args []parse.Node, final reflect.Value) reflect.Value {
+ s.at(field)
+ return s.evalFieldChain(dot, dot, field, field.Ident, args, final)
+}
+
+func (s *state) evalChainNode(dot reflect.Value, chain *parse.ChainNode, args []parse.Node, final reflect.Value) reflect.Value {
+ s.at(chain)
+ if len(chain.Field) == 0 {
+ s.errorf("internal error: no fields in evalChainNode")
+ }
+ if chain.Node.Type() == parse.NodeNil {
+ s.errorf("indirection through explicit nil in %s", chain)
+ }
+ // (pipe).Field1.Field2 has pipe as .Node, fields as .Field. Eval the pipeline, then the fields.
+ pipe := s.evalArg(dot, nil, chain.Node)
+ return s.evalFieldChain(dot, pipe, chain, chain.Field, args, final)
+}
+
+func (s *state) evalVariableNode(dot reflect.Value, variable *parse.VariableNode, args []parse.Node, final reflect.Value) reflect.Value {
+ // $x.Field has $x as the first ident, Field as the second. Eval the var, then the fields.
+ s.at(variable)
+ value := s.varValue(variable.Ident[0])
+ if len(variable.Ident) == 1 {
+ s.notAFunction(args, final)
+ return value
+ }
+ return s.evalFieldChain(dot, value, variable, variable.Ident[1:], args, final)
+}
+
+// evalFieldChain evaluates .X.Y.Z possibly followed by arguments.
+// dot is the environment in which to evaluate arguments, while
+// receiver is the value being walked along the chain.
+func (s *state) evalFieldChain(dot, receiver reflect.Value, node parse.Node, ident []string, args []parse.Node, final reflect.Value) reflect.Value {
+ n := len(ident)
+ for i := 0; i < n-1; i++ {
+ receiver = s.evalField(dot, ident[i], node, nil, missingVal, receiver)
+ }
+ // Now if it's a method, it gets the arguments.
+ return s.evalField(dot, ident[n-1], node, args, final, receiver)
+}
+
+func (s *state) evalFunction(dot reflect.Value, node *parse.IdentifierNode, cmd parse.Node, args []parse.Node, final reflect.Value) reflect.Value {
+ s.at(node)
+ name := node.Ident
+ function, isBuiltin, ok := findFunction(name, s.tmpl)
+ if !ok {
+ s.errorf("%q is not a defined function", name)
+ }
+ return s.evalCall(dot, function, isBuiltin, cmd, name, args, final)
+}
+
+// evalField evaluates an expression like (.Field) or (.Field arg1 arg2).
+// The 'final' argument represents the return value from the preceding
+// value of the pipeline, if any.
+func (s *state) evalField(dot reflect.Value, fieldName string, node parse.Node, args []parse.Node, final, receiver reflect.Value) reflect.Value {
+ if !receiver.IsValid() {
+ if s.tmpl.option.missingKey == mapError { // Treat invalid value as missing map key.
+ s.errorf("nil data; no entry for key %q", fieldName)
+ }
+ return zero
+ }
+ typ := receiver.Type()
+ receiver, isNil := indirect(receiver)
+ if receiver.Kind() == reflect.Interface && isNil {
+ // Calling a method on a nil interface can't work. The
+ // MethodByName method call below would panic.
+ s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
+ return zero
+ }
+
+ // Unless it's an interface, need to get to a value of type *T to guarantee
+ // we see all methods of T and *T.
+ ptr := receiver
+ if ptr.Kind() != reflect.Interface && ptr.Kind() != reflect.Pointer && ptr.CanAddr() {
+ ptr = ptr.Addr()
+ }
+ if method := ptr.MethodByName(fieldName); method.IsValid() {
+ return s.evalCall(dot, method, false, node, fieldName, args, final)
+ }
+ hasArgs := len(args) > 1 || !isMissing(final)
+ // It's not a method; must be a field of a struct or an element of a map.
+ switch receiver.Kind() {
+ case reflect.Struct:
+ tField, ok := receiver.Type().FieldByName(fieldName)
+ if ok {
+ field, err := receiver.FieldByIndexErr(tField.Index)
+ if !tField.IsExported() {
+ s.errorf("%s is an unexported field of struct type %s", fieldName, typ)
+ }
+ if err != nil {
+ s.errorf("%v", err)
+ }
+ // If it's a function, we must call it.
+ if hasArgs {
+ s.errorf("%s has arguments but cannot be invoked as function", fieldName)
+ }
+ return field
+ }
+ case reflect.Map:
+ // If it's a map, attempt to use the field name as a key.
+ nameVal := reflect.ValueOf(fieldName)
+ if nameVal.Type().AssignableTo(receiver.Type().Key()) {
+ if hasArgs {
+ s.errorf("%s is not a method but has arguments", fieldName)
+ }
+ result := receiver.MapIndex(nameVal)
+ if !result.IsValid() {
+ switch s.tmpl.option.missingKey {
+ case mapInvalid:
+ // Just use the invalid value.
+ case mapZeroValue:
+ result = reflect.Zero(receiver.Type().Elem())
+ case mapError:
+ s.errorf("map has no entry for key %q", fieldName)
+ }
+ }
+ return result
+ }
+ case reflect.Pointer:
+ etyp := receiver.Type().Elem()
+ if etyp.Kind() == reflect.Struct {
+ if _, ok := etyp.FieldByName(fieldName); !ok {
+ // If there's no such field, say "can't evaluate"
+ // instead of "nil pointer evaluating".
+ break
+ }
+ }
+ if isNil {
+ s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
+ }
+ }
+ s.errorf("can't evaluate field %s in type %s", fieldName, typ)
+ panic("not reached")
+}
+
+var (
+ errorType = reflect.TypeOf((*error)(nil)).Elem()
+ fmtStringerType = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
+ reflectValueType = reflect.TypeOf((*reflect.Value)(nil)).Elem()
+)
+
+// evalCall executes a function or method call. If it's a method, fun already has the receiver bound, so
+// it looks just like a function call. The arg list, if non-nil, includes (in the manner of the shell), arg[0]
+// as the function itself.
+func (s *state) evalCall(dot, fun reflect.Value, isBuiltin bool, node parse.Node, name string, args []parse.Node, final reflect.Value) reflect.Value {
+ if args != nil {
+ args = args[1:] // Zeroth arg is function name/node; not passed to function.
+ }
+ typ := fun.Type()
+ numIn := len(args)
+ if !isMissing(final) {
+ numIn++
+ }
+ numFixed := len(args)
+ if typ.IsVariadic() {
+ numFixed = typ.NumIn() - 1 // last arg is the variadic one.
+ if numIn < numFixed {
+ s.errorf("wrong number of args for %s: want at least %d got %d", name, typ.NumIn()-1, len(args))
+ }
+ } else if numIn != typ.NumIn() {
+ s.errorf("wrong number of args for %s: want %d got %d", name, typ.NumIn(), numIn)
+ }
+ if !goodFunc(typ) {
+ // TODO: This could still be a confusing error; maybe goodFunc should provide info.
+ s.errorf("can't call method/function %q with %d results", name, typ.NumOut())
+ }
+
+ unwrap := func(v reflect.Value) reflect.Value {
+ if v.Type() == reflectValueType {
+ v = v.Interface().(reflect.Value)
+ }
+ return v
+ }
+
+ // Special case for builtin and/or, which short-circuit.
+ if isBuiltin && (name == "and" || name == "or") {
+ argType := typ.In(0)
+ var v reflect.Value
+ for _, arg := range args {
+ v = s.evalArg(dot, argType, arg).Interface().(reflect.Value)
+ if truth(v) == (name == "or") {
+ // This value was already unwrapped
+ // by the .Interface().(reflect.Value).
+ return v
+ }
+ }
+ if final != missingVal {
+ // The last argument to and/or is coming from
+ // the pipeline. We didn't short circuit on an earlier
+ // argument, so we are going to return this one.
+ // We don't have to evaluate final, but we do
+ // have to check its type. Then, since we are
+ // going to return it, we have to unwrap it.
+ v = unwrap(s.validateType(final, argType))
+ }
+ return v
+ }
+
+ // Build the arg list.
+ argv := make([]reflect.Value, numIn)
+ // Args must be evaluated. Fixed args first.
+ i := 0
+ for ; i < numFixed && i < len(args); i++ {
+ argv[i] = s.evalArg(dot, typ.In(i), args[i])
+ }
+ // Now the ... args.
+ if typ.IsVariadic() {
+ argType := typ.In(typ.NumIn() - 1).Elem() // Argument is a slice.
+ for ; i < len(args); i++ {
+ argv[i] = s.evalArg(dot, argType, args[i])
+ }
+ }
+ // Add final value if necessary.
+ if !isMissing(final) {
+ t := typ.In(typ.NumIn() - 1)
+ if typ.IsVariadic() {
+ if numIn-1 < numFixed {
+ // The added final argument corresponds to a fixed parameter of the function.
+ // Validate against the type of the actual parameter.
+ t = typ.In(numIn - 1)
+ } else {
+ // The added final argument corresponds to the variadic part.
+ // Validate against the type of the elements of the variadic slice.
+ t = t.Elem()
+ }
+ }
+ argv[i] = s.validateType(final, t)
+ }
+ v, err := safeCall(fun, argv)
+ // If we have an error that is not nil, stop execution and return that
+ // error to the caller.
+ if err != nil {
+ s.at(node)
+ s.errorf("error calling %s: %w", name, err)
+ }
+ return unwrap(v)
+}
+
+// canBeNil reports whether an untyped nil can be assigned to the type. See reflect.Zero.
+func canBeNil(typ reflect.Type) bool {
+ switch typ.Kind() {
+ case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Pointer, reflect.Slice:
+ return true
+ case reflect.Struct:
+ return typ == reflectValueType
+ }
+ return false
+}
+
+// validateType guarantees that the value is valid and assignable to the type.
+func (s *state) validateType(value reflect.Value, typ reflect.Type) reflect.Value {
+ if !value.IsValid() {
+ if typ == nil {
+ // An untyped nil interface{}. Accept as a proper nil value.
+ return reflect.ValueOf(nil)
+ }
+ if canBeNil(typ) {
+ // Like above, but use the zero value of the non-nil type.
+ return reflect.Zero(typ)
+ }
+ s.errorf("invalid value; expected %s", typ)
+ }
+ if typ == reflectValueType && value.Type() != typ {
+ return reflect.ValueOf(value)
+ }
+ if typ != nil && !value.Type().AssignableTo(typ) {
+ if value.Kind() == reflect.Interface && !value.IsNil() {
+ value = value.Elem()
+ if value.Type().AssignableTo(typ) {
+ return value
+ }
+ // fallthrough
+ }
+ // Does one dereference or indirection work? We could do more, as we
+ // do with method receivers, but that gets messy and method receivers
+ // are much more constrained, so it makes more sense there than here.
+ // Besides, one is almost always all you need.
+ switch {
+ case value.Kind() == reflect.Pointer && value.Type().Elem().AssignableTo(typ):
+ value = value.Elem()
+ if !value.IsValid() {
+ s.errorf("dereference of nil pointer of type %s", typ)
+ }
+ case reflect.PointerTo(value.Type()).AssignableTo(typ) && value.CanAddr():
+ value = value.Addr()
+ default:
+ s.errorf("wrong type for value; expected %s; got %s", typ, value.Type())
+ }
+ }
+ return value
+}
+
+func (s *state) evalArg(dot reflect.Value, typ reflect.Type, n parse.Node) reflect.Value {
+ s.at(n)
+ switch arg := n.(type) {
+ case *parse.DotNode:
+ return s.validateType(dot, typ)
+ case *parse.NilNode:
+ if canBeNil(typ) {
+ return reflect.Zero(typ)
+ }
+ s.errorf("cannot assign nil to %s", typ)
+ case *parse.FieldNode:
+ return s.validateType(s.evalFieldNode(dot, arg, []parse.Node{n}, missingVal), typ)
+ case *parse.VariableNode:
+ return s.validateType(s.evalVariableNode(dot, arg, nil, missingVal), typ)
+ case *parse.PipeNode:
+ return s.validateType(s.evalPipeline(dot, arg), typ)
+ case *parse.IdentifierNode:
+ return s.validateType(s.evalFunction(dot, arg, arg, nil, missingVal), typ)
+ case *parse.ChainNode:
+ return s.validateType(s.evalChainNode(dot, arg, nil, missingVal), typ)
+ }
+ switch typ.Kind() {
+ case reflect.Bool:
+ return s.evalBool(typ, n)
+ case reflect.Complex64, reflect.Complex128:
+ return s.evalComplex(typ, n)
+ case reflect.Float32, reflect.Float64:
+ return s.evalFloat(typ, n)
+ case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+ return s.evalInteger(typ, n)
+ case reflect.Interface:
+ if typ.NumMethod() == 0 {
+ return s.evalEmptyInterface(dot, n)
+ }
+ case reflect.Struct:
+ if typ == reflectValueType {
+ return reflect.ValueOf(s.evalEmptyInterface(dot, n))
+ }
+ case reflect.String:
+ return s.evalString(typ, n)
+ case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+ return s.evalUnsignedInteger(typ, n)
+ }
+ s.errorf("can't handle %s for arg of type %s", n, typ)
+ panic("not reached")
+}
+
+func (s *state) evalBool(typ reflect.Type, n parse.Node) reflect.Value {
+ s.at(n)
+ if n, ok := n.(*parse.BoolNode); ok {
+ value := reflect.New(typ).Elem()
+ value.SetBool(n.True)
+ return value
+ }
+ s.errorf("expected bool; found %s", n)
+ panic("not reached")
+}
+
+func (s *state) evalString(typ reflect.Type, n parse.Node) reflect.Value {
+ s.at(n)
+ if n, ok := n.(*parse.StringNode); ok {
+ value := reflect.New(typ).Elem()
+ value.SetString(n.Text)
+ return value
+ }
+ s.errorf("expected string; found %s", n)
+ panic("not reached")
+}
+
+func (s *state) evalInteger(typ reflect.Type, n parse.Node) reflect.Value {
+ s.at(n)
+ if n, ok := n.(*parse.NumberNode); ok && n.IsInt {
+ value := reflect.New(typ).Elem()
+ value.SetInt(n.Int64)
+ return value
+ }
+ s.errorf("expected integer; found %s", n)
+ panic("not reached")
+}
+
+func (s *state) evalUnsignedInteger(typ reflect.Type, n parse.Node) reflect.Value {
+ s.at(n)
+ if n, ok := n.(*parse.NumberNode); ok && n.IsUint {
+ value := reflect.New(typ).Elem()
+ value.SetUint(n.Uint64)
+ return value
+ }
+ s.errorf("expected unsigned integer; found %s", n)
+ panic("not reached")
+}
+
+func (s *state) evalFloat(typ reflect.Type, n parse.Node) reflect.Value {
+ s.at(n)
+ if n, ok := n.(*parse.NumberNode); ok && n.IsFloat {
+ value := reflect.New(typ).Elem()
+ value.SetFloat(n.Float64)
+ return value
+ }
+ s.errorf("expected float; found %s", n)
+ panic("not reached")
+}
+
+func (s *state) evalComplex(typ reflect.Type, n parse.Node) reflect.Value {
+ if n, ok := n.(*parse.NumberNode); ok && n.IsComplex {
+ value := reflect.New(typ).Elem()
+ value.SetComplex(n.Complex128)
+ return value
+ }
+ s.errorf("expected complex; found %s", n)
+ panic("not reached")
+}
+
+func (s *state) evalEmptyInterface(dot reflect.Value, n parse.Node) reflect.Value {
+ s.at(n)
+ switch n := n.(type) {
+ case *parse.BoolNode:
+ return reflect.ValueOf(n.True)
+ case *parse.DotNode:
+ return dot
+ case *parse.FieldNode:
+ return s.evalFieldNode(dot, n, nil, missingVal)
+ case *parse.IdentifierNode:
+ return s.evalFunction(dot, n, n, nil, missingVal)
+ case *parse.NilNode:
+ // NilNode is handled in evalArg, the only place that calls here.
+ s.errorf("evalEmptyInterface: nil (can't happen)")
+ case *parse.NumberNode:
+ return s.idealConstant(n)
+ case *parse.StringNode:
+ return reflect.ValueOf(n.Text)
+ case *parse.VariableNode:
+ return s.evalVariableNode(dot, n, nil, missingVal)
+ case *parse.PipeNode:
+ return s.evalPipeline(dot, n)
+ }
+ s.errorf("can't handle assignment of %s to empty interface argument", n)
+ panic("not reached")
+}
+
+// indirect returns the item at the end of indirection, and a bool to indicate
+// if it's nil. If the returned bool is true, the returned value's kind will be
+// either a pointer or interface.
+func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
+ for ; v.Kind() == reflect.Pointer || v.Kind() == reflect.Interface; v = v.Elem() {
+ if v.IsNil() {
+ return v, true
+ }
+ }
+ return v, false
+}
+
+// indirectInterface returns the concrete value in an interface value,
+// or else the zero reflect.Value.
+// That is, if v represents the interface value x, the result is the same as reflect.ValueOf(x):
+// the fact that x was an interface value is forgotten.
+func indirectInterface(v reflect.Value) reflect.Value {
+ if v.Kind() != reflect.Interface {
+ return v
+ }
+ if v.IsNil() {
+ return reflect.Value{}
+ }
+ return v.Elem()
+}
+
+// printValue writes the textual representation of the value to the output of
+// the template.
+func (s *state) printValue(n parse.Node, v reflect.Value) {
+ s.at(n)
+ iface, ok := printableValue(v)
+ if !ok {
+ s.errorf("can't print %s of type %s", n, v.Type())
+ }
+ _, err := fmt.Fprint(s.wr, iface)
+ if err != nil {
+ s.writeError(err)
+ }
+}
+
+// printableValue returns the, possibly indirected, interface value inside v that
+// is best for a call to formatted printer.
+func printableValue(v reflect.Value) (any, bool) {
+ if v.Kind() == reflect.Pointer {
+ v, _ = indirect(v) // fmt.Fprint handles nil.
+ }
+ if !v.IsValid() {
+ return "<no value>", true
+ }
+
+ if !v.Type().Implements(errorType) && !v.Type().Implements(fmtStringerType) {
+ if v.CanAddr() && (reflect.PointerTo(v.Type()).Implements(errorType) || reflect.PointerTo(v.Type()).Implements(fmtStringerType)) {
+ v = v.Addr()
+ } else {
+ switch v.Kind() {
+ case reflect.Chan, reflect.Func:
+ return nil, false
+ }
+ }
+ }
+ return v.Interface(), true
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-03 07:16:51 +0000