param.go

// Copyright (c) 2019-2021 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package dig

import (
	"fmt"
	"reflect"
	"strconv"
	"strings"

	"go.uber.org/dig/internal/digerror"
	"go.uber.org/dig/internal/dot"
)

// The param interface represents a dependency for a constructor.
//
// The following implementations exist:
//
//	paramList     All arguments of the constructor.
//	paramSingle   An explicitly requested type.
//	paramObject   dig.In struct where each field in the struct can be another
//	              param.
//	paramGroupedSlice
//	              A slice consuming a value group. This will receive all
//	              values produced with a `group:".."` tag with the same name
//	              as a slice.
type param interface {
	fmt.Stringer

	// Build this dependency and any of its dependencies from the provided
	// Container.
	//
	// This MAY panic if the param does not produce a single value.
	Build(store containerStore) (reflect.Value, error)

	// DotParam returns a slice of dot.Param(s).
	DotParam() []*dot.Param
}

var (
	_ param = paramSingle{}
	_ param = paramObject{}
	_ param = paramList{}
	_ param = paramGroupedSlice{}
)

// newParam builds a param from the given type. If the provided type is a
// dig.In struct, an paramObject will be returned.
func newParam(t reflect.Type, c containerStore) (param, error) {
	switch {
	case IsOut(t) || (t.Kind() == reflect.Ptr && IsOut(t.Elem())) || embedsType(t, _outPtrType):
		return nil, newErrInvalidInput(fmt.Sprintf(
			"cannot depend on result objects: %v embeds a dig.Out", t), nil)
	case IsIn(t):
		return newParamObject(t, c)
	case embedsType(t, _inPtrType):
		return nil, newErrInvalidInput(fmt.Sprintf(
			"cannot build a parameter object by embedding *dig.In, embed dig.In instead: %v embeds *dig.In", t), nil)
	case t.Kind() == reflect.Ptr && IsIn(t.Elem()):
		return nil, newErrInvalidInput(fmt.Sprintf(
			"cannot depend on a pointer to a parameter object, use a value instead: %v is a pointer to a struct that embeds dig.In", t), nil)
	default:
		return paramSingle{Type: t}, nil
	}
}

// paramList holds all arguments of the constructor as params.
//
// NOTE: Build() MUST NOT be called on paramList. Instead, BuildList
// must be called.
type paramList struct {
	ctype reflect.Type // type of the constructor

	Params []param
}

func (pl paramList) DotParam() []*dot.Param {
	var types []*dot.Param
	for _, param := range pl.Params {
		types = append(types, param.DotParam()...)
	}
	return types
}

func (pl paramList) String() string {
	args := make([]string, len(pl.Params))
	for i, p := range pl.Params {
		args[i] = p.String()
	}
	return fmt.Sprint(args)
}

// newParamList builds a paramList from the provided constructor type.
//
// Variadic arguments of a constructor are ignored and not included as
// dependencies.
func newParamList(ctype reflect.Type, c containerStore) (paramList, error) {
	numArgs := ctype.NumIn()
	if ctype.IsVariadic() {
		// NOTE: If the function is variadic, we skip the last argument
		// because we're not filling variadic arguments yet. See #120.
		numArgs--
	}

	pl := paramList{
		ctype:  ctype,
		Params: make([]param, 0, numArgs),
	}

	for i := 0; i < numArgs; i++ {
		p, err := newParam(ctype.In(i), c)
		if err != nil {
			return pl, newErrInvalidInput(fmt.Sprintf("bad argument %d", i+1), err)
		}
		pl.Params = append(pl.Params, p)
	}

	return pl, nil
}

func (pl paramList) Build(containerStore) (reflect.Value, error) {
	digerror.BugPanicf("paramList.Build() must never be called")
	panic("") // Unreachable, as BugPanicf above will panic.
}

// BuildList returns an ordered list of values which may be passed directly
// to the underlying constructor.
func (pl paramList) BuildList(c containerStore) ([]reflect.Value, error) {
	args := make([]reflect.Value, len(pl.Params))
	for i, p := range pl.Params {
		var err error
		args[i], err = p.Build(c)
		if err != nil {
			return nil, err
		}
	}
	return args, nil
}

// paramSingle is an explicitly requested type, optionally with a name.
//
// This object must be present in the graph as-is unless it's specified as
// optional.
type paramSingle struct {
	Name     string
	Optional bool
	Type     reflect.Type
}

func (ps paramSingle) DotParam() []*dot.Param {
	return []*dot.Param{
		{
			Node: &dot.Node{
				Type: ps.Type,
				Name: ps.Name,
			},
			Optional: ps.Optional,
		},
	}
}

func (ps paramSingle) String() string {
	// tally.Scope[optional] means optional
	// tally.Scope[optional, name="foo"] means named optional

	var opts []string
	if ps.Optional {
		opts = append(opts, "optional")
	}
	if ps.Name != "" {
		opts = append(opts, fmt.Sprintf("name=%q", ps.Name))
	}

	if len(opts) == 0 {
		return fmt.Sprint(ps.Type)
	}

	return fmt.Sprintf("%v[%v]", ps.Type, strings.Join(opts, ", "))
}

// search the given container and its ancestors for a decorated value.
func (ps paramSingle) getDecoratedValue(c containerStore) (reflect.Value, bool) {
	for _, c := range c.storesToRoot() {
		if v, ok := c.getDecoratedValue(ps.Name, ps.Type); ok {
			return v, ok
		}
	}
	return _noValue, false
}

// builds the parameter using decorators in all scopes that affect the
// current scope, if there are any. If there are multiple Scopes that decorates
// this parameter, the closest one to the Scope that invoked this will be used.
// If there are no decorators associated with this parameter, _noValue is returned.
func (ps paramSingle) buildWithDecorators(c containerStore) (v reflect.Value, found bool, err error) {
	var (
		d               decorator
		decoratingScope containerStore
	)
	stores := c.storesToRoot()

	for _, s := range stores {
		if d, found = s.getValueDecorator(ps.Name, ps.Type); !found {
			continue
		}
		if d.State() == decoratorOnStack {
			// This decorator is already being run.
			// Avoid a cycle and look further.
			d = nil
			continue
		}
		decoratingScope = s
		break
	}
	if !found || d == nil {
		return _noValue, false, nil
	}
	if err = d.Call(decoratingScope); err != nil {
		v, err = _noValue, errParamSingleFailed{
			CtorID: 1,
			Key:    key{t: ps.Type, name: ps.Name},
			Reason: err,
		}
		return v, found, err
	}
	v, _ = decoratingScope.getDecoratedValue(ps.Name, ps.Type)
	return
}

func (ps paramSingle) Build(c containerStore) (reflect.Value, error) {
	v, found, err := ps.buildWithDecorators(c)
	if found {
		return v, err
	}

	// Check whether the value is a decorated value first.
	if v, ok := ps.getDecoratedValue(c); ok {
		return v, nil
	}

	// Starting at the given container and working our way up its parents,
	// find one that provides this dependency.
	//
	// Once found, we'll use that container for the rest of the invocation.
	// Dependencies of this type will begin searching at that container,
	// rather than starting at base.
	var providers []provider
	var providingContainer containerStore
	for _, container := range c.storesToRoot() {
		// first check if the scope already has cached a value for the type.
		if v, ok := container.getValue(ps.Name, ps.Type); ok {
			return v, nil
		}
		providers = container.getValueProviders(ps.Name, ps.Type)
		if len(providers) > 0 {
			providingContainer = container
			break
		}
	}

	if len(providers) == 0 {
		if ps.Optional {
			return reflect.Zero(ps.Type), nil
		}
		return _noValue, newErrMissingTypes(c, key{name: ps.Name, t: ps.Type})
	}

	for _, n := range providers {
		err := n.Call(n.OrigScope())
		if err == nil {
			continue
		}

		// If we're missing dependencies but the parameter itself is optional,
		// we can just move on.
		if _, ok := err.(errMissingDependencies); ok && ps.Optional {
			return reflect.Zero(ps.Type), nil
		}

		return _noValue, errParamSingleFailed{
			CtorID: n.ID(),
			Key:    key{t: ps.Type, name: ps.Name},
			Reason: err,
		}
	}

	// If we get here, it's impossible for the value to be absent from the
	// container.
	v, _ = providingContainer.getValue(ps.Name, ps.Type)
	return v, nil
}

// paramObject is a dig.In struct where each field is another param.
//
// This object is not expected in the graph as-is.
type paramObject struct {
	Type        reflect.Type
	Fields      []paramObjectField
	FieldOrders []int
}

func (po paramObject) DotParam() []*dot.Param {
	var types []*dot.Param
	for _, field := range po.Fields {
		types = append(types, field.DotParam()...)
	}
	return types
}

func (po paramObject) String() string {
	fields := make([]string, len(po.Fields))
	for i, f := range po.Fields {
		fields[i] = f.Param.String()
	}
	return strings.Join(fields, " ")
}

// getParamOrder returns the order(s) of a parameter type.
func getParamOrder(gh *graphHolder, param param) []int {
	var orders []int
	switch p := param.(type) {
	case paramSingle:
		providers := gh.s.getAllValueProviders(p.Name, p.Type)
		for _, provider := range providers {
			orders = append(orders, provider.Order(gh.s))
		}
	case paramGroupedSlice:
		// value group parameters have nodes of their own.
		// We can directly return that here.
		orders = append(orders, p.orders[gh.s])
	case paramObject:
		for _, pf := range p.Fields {
			orders = append(orders, getParamOrder(gh, pf.Param)...)
		}
	}
	return orders
}

// newParamObject builds an paramObject from the provided type. The type MUST
// be a dig.In struct.
func newParamObject(t reflect.Type, c containerStore) (paramObject, error) {
	po := paramObject{Type: t}

	// Check if the In type supports ignoring unexported fields.
	var ignoreUnexported bool
	for i := 0; i < t.NumField(); i++ {
		f := t.Field(i)
		if f.Type == _inType {
			var err error
			ignoreUnexported, err = isIgnoreUnexportedSet(f)
			if err != nil {
				return po, err
			}
			break
		}
	}

	for i := 0; i < t.NumField(); i++ {
		f := t.Field(i)
		if f.Type == _inType {
			// Skip over the dig.In embed.
			continue
		}
		if f.PkgPath != "" && ignoreUnexported {
			// Skip over an unexported field if it is allowed.
			continue
		}
		pof, err := newParamObjectField(i, f, c)
		if err != nil {
			return po, newErrInvalidInput(
				fmt.Sprintf("bad field %q of %v", f.Name, t), err)
		}
		po.Fields = append(po.Fields, pof)
	}
	return po, nil
}

func (po paramObject) Build(c containerStore) (reflect.Value, error) {
	dest := reflect.New(po.Type).Elem()
	// We have to build soft groups after all other fields, to avoid cases
	// when a field calls a provider for a soft value group, but the value is
	// not provided to it because the value group is declared before the field
	var softGroupsQueue []paramObjectField
	var fields []paramObjectField
	for _, f := range po.Fields {
		if p, ok := f.Param.(paramGroupedSlice); ok && p.Soft {
			softGroupsQueue = append(softGroupsQueue, f)
			continue
		}
		fields = append(fields, f)
	}
	fields = append(fields, softGroupsQueue...)
	for _, f := range fields {
		v, err := f.Build(c)
		if err != nil {
			return dest, err
		}
		dest.Field(f.FieldIndex).Set(v)
	}
	return dest, nil
}

// paramObjectField is a single field of a dig.In struct.
type paramObjectField struct {
	// Name of the field in the struct.
	FieldName string

	// Index of this field in the target struct.
	//
	// We need to track this separately because not all fields of the
	// struct map to params.
	FieldIndex int

	// The dependency requested by this field.
	Param param
}

func (pof paramObjectField) DotParam() []*dot.Param {
	return pof.Param.DotParam()
}

func newParamObjectField(idx int, f reflect.StructField, c containerStore) (paramObjectField, error) {
	pof := paramObjectField{
		FieldName:  f.Name,
		FieldIndex: idx,
	}

	var p param
	switch {
	case f.PkgPath != "":
		return pof, newErrInvalidInput(
			fmt.Sprintf("unexported fields not allowed in dig.In, did you mean to export %q (%v)?", f.Name, f.Type), nil)

	case f.Tag.Get(_groupTag) != "":
		var err error
		p, err = newParamGroupedSlice(f, c)
		if err != nil {
			return pof, err
		}

	default:
		var err error
		p, err = newParam(f.Type, c)
		if err != nil {
			return pof, err
		}
	}

	if ps, ok := p.(paramSingle); ok {
		ps.Name = f.Tag.Get(_nameTag)

		var err error
		ps.Optional, err = isFieldOptional(f)
		if err != nil {
			return pof, err
		}

		p = ps
	}

	pof.Param = p
	return pof, nil
}

func (pof paramObjectField) Build(c containerStore) (reflect.Value, error) {
	v, err := pof.Param.Build(c)
	if err != nil {
		return v, err
	}
	return v, nil
}

// paramGroupedSlice is a param which produces a slice of values with the same
// group name.
type paramGroupedSlice struct {
	// Name of the group as specified in the `group:".."` tag.
	Group string

	// Type of the slice.
	Type reflect.Type

	// Soft is used to denote a soft dependency between this param and its
	// constructors, if it's true its constructors are only called if they
	// provide another value requested in the graph
	Soft bool

	orders map[*Scope]int
}

func (pt paramGroupedSlice) String() string {
	// io.Reader[group="foo"] refers to a group of io.Readers called 'foo'
	return fmt.Sprintf("%v[group=%q]", pt.Type.Elem(), pt.Group)
}

func (pt paramGroupedSlice) DotParam() []*dot.Param {
	return []*dot.Param{
		{
			Node: &dot.Node{
				Type:  pt.Type,
				Group: pt.Group,
			},
		},
	}
}

// newParamGroupedSlice builds a paramGroupedSlice from the provided type with
// the given name.
//
// The type MUST be a slice type.
func newParamGroupedSlice(f reflect.StructField, c containerStore) (paramGroupedSlice, error) {
	g, err := parseGroupString(f.Tag.Get(_groupTag))
	if err != nil {
		return paramGroupedSlice{}, err
	}
	pg := paramGroupedSlice{
		Group:  g.Name,
		Type:   f.Type,
		orders: make(map[*Scope]int),
		Soft:   g.Soft,
	}

	name := f.Tag.Get(_nameTag)
	optional, _ := isFieldOptional(f)
	switch {
	case f.Type.Kind() != reflect.Slice:
		return pg, newErrInvalidInput(
			fmt.Sprintf("value groups may be consumed as slices only: field %q (%v) is not a slice", f.Name, f.Type), nil)
	case g.Flatten:
		return pg, newErrInvalidInput(
			fmt.Sprintf("cannot use flatten in parameter value groups: field %q (%v) specifies flatten", f.Name, f.Type), nil)
	case name != "":
		return pg, newErrInvalidInput(
			fmt.Sprintf("cannot use named values with value groups: name:%q requested with group:%q", name, pg.Group), nil)
	case optional:
		return pg, newErrInvalidInput("value groups cannot be optional", nil)
	}
	c.newGraphNode(&pg, pg.orders)
	return pg, nil
}

// retrieves any decorated values that may be committed in this scope, or
// any of the parent Scopes. In the case where there are multiple scopes that
// are decorating the same type, the closest scope in effect will be replacing
// any decorated value groups provided in further scopes.
func (pt paramGroupedSlice) getDecoratedValues(c containerStore) (reflect.Value, bool) {
	for _, c := range c.storesToRoot() {
		if items, ok := c.getDecoratedValueGroup(pt.Group, pt.Type); ok {
			return items, true
		}
	}
	return _noValue, false
}

// search the given container and its parents for matching group decorators
// and call them to commit values. If any decorators return an error,
// that error is returned immediately. If all decorators succeeds, nil is returned.
// The order in which the decorators are invoked is from the top level scope to
// the current scope, to account for decorators that decorate values that were
// already decorated.
func (pt paramGroupedSlice) callGroupDecorators(c containerStore) error {
	stores := c.storesToRoot()
	for i := len(stores) - 1; i >= 0; i-- {
		c := stores[i]
		if d, found := c.getGroupDecorator(pt.Group, pt.Type.Elem()); found {
			if d.State() == decoratorOnStack {
				// This decorator is already being run. Avoid cycle
				// and look further.
				continue
			}
			if err := d.Call(c); err != nil {
				return errParamGroupFailed{
					CtorID: d.ID(),
					Key:    key{group: pt.Group, t: pt.Type.Elem()},
					Reason: err,
				}
			}
		}
	}
	return nil
}

// search the given container and its parent for matching group providers and
// call them to commit values. If an error is encountered, return the number
// of providers called and a non-nil error from the first provided.
func (pt paramGroupedSlice) callGroupProviders(c containerStore) (int, error) {
	itemCount := 0
	for _, c := range c.storesToRoot() {
		providers := c.getGroupProviders(pt.Group, pt.Type.Elem())
		itemCount += len(providers)
		for _, n := range providers {
			if err := n.Call(c); err != nil {
				return 0, errParamGroupFailed{
					CtorID: n.ID(),
					Key:    key{group: pt.Group, t: pt.Type.Elem()},
					Reason: err,
				}
			}
		}
	}
	return itemCount, nil
}

func (pt paramGroupedSlice) Build(c containerStore) (reflect.Value, error) {
	// do not call this if we are already inside a decorator since
	// it will result in an infinite recursion. (i.e. decorate -> params.BuildList() -> Decorate -> params.BuildList...)
	// this is safe since a value can be decorated at most once in a given scope.
	if err := pt.callGroupDecorators(c); err != nil {
		return _noValue, err
	}

	// Check if we have decorated values
	if decoratedItems, ok := pt.getDecoratedValues(c); ok {
		return decoratedItems, nil
	}

	// If we do not have any decorated values and the group isn't soft,
	// find the providers and call them.
	itemCount := 0
	if !pt.Soft {
		var err error
		itemCount, err = pt.callGroupProviders(c)
		if err != nil {
			return _noValue, err
		}
	}

	stores := c.storesToRoot()
	result := reflect.MakeSlice(pt.Type, 0, itemCount)
	for _, c := range stores {
		result = reflect.Append(result, c.getValueGroup(pt.Group, pt.Type.Elem())...)
	}
	return result, nil
}

// Checks if ignoring unexported files in an In struct is allowed.
// The struct field MUST be an _inType.
func isIgnoreUnexportedSet(f reflect.StructField) (bool, error) {
	tag := f.Tag.Get(_ignoreUnexportedTag)
	if tag == "" {
		return false, nil
	}

	allowed, err := strconv.ParseBool(tag)
	if err != nil {
		err = newErrInvalidInput(
			fmt.Sprintf("invalid value %q for %q tag on field %v", tag, _ignoreUnexportedTag, f.Name), err)
	}

	return allowed, err
}