165 lines
3.9 KiB
Go
165 lines
3.9 KiB
Go
package depinject
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import (
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"reflect"
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"strings"
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"unicode"
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"github.com/pkg/errors"
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"golang.org/x/exp/slices"
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)
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// providerDescriptor defines a special provider type that is defined by
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// reflection. It should be passed as a value to the Provide function.
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// Ex:
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//
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// option.Provide(providerDescriptor{ ... })
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type providerDescriptor struct {
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// Inputs defines the in parameter types to Fn.
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Inputs []providerInput
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// Outputs defines the out parameter types to Fn.
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Outputs []providerOutput
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// Fn defines the provider function.
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Fn func([]reflect.Value) ([]reflect.Value, error)
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// Location defines the source code location to be used for this provider
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// in error messages.
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Location Location
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}
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type providerInput struct {
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Type reflect.Type
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Optional bool
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}
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type providerOutput struct {
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Type reflect.Type
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}
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func extractProviderDescriptor(provider interface{}) (providerDescriptor, error) {
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rctr, err := doExtractProviderDescriptor(provider)
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if err != nil {
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return providerDescriptor{}, err
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}
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return postProcessProvider(rctr)
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}
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func extractInvokerDescriptor(provider interface{}) (providerDescriptor, error) {
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rctr, err := doExtractProviderDescriptor(provider)
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if err != nil {
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return providerDescriptor{}, err
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}
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// mark all inputs as optional
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for i, input := range rctr.Inputs {
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input.Optional = true
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rctr.Inputs[i] = input
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}
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return postProcessProvider(rctr)
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}
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func doExtractProviderDescriptor(ctr interface{}) (providerDescriptor, error) {
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val := reflect.ValueOf(ctr)
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typ := val.Type()
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if typ.Kind() != reflect.Func {
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return providerDescriptor{}, errors.Errorf("expected a Func type, got %v", typ)
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}
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loc := LocationFromPC(val.Pointer()).(*location)
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nameParts := strings.Split(loc.name, ".")
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if len(nameParts) == 0 {
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return providerDescriptor{}, errors.Errorf("missing function name %s", loc)
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}
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lastNamePart := nameParts[len(nameParts)-1]
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if unicode.IsLower([]rune(lastNamePart)[0]) {
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return providerDescriptor{}, errors.Errorf("function must be exported: %s", loc)
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}
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if strings.Contains(lastNamePart, "-") {
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return providerDescriptor{}, errors.Errorf("function can't be used as a provider (it might be a bound instance method): %s", loc)
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}
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pkgParts := strings.Split(loc.pkg, "/")
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if slices.Contains(pkgParts, "internal") {
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return providerDescriptor{}, errors.Errorf("function must not be in an internal package: %s", loc)
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}
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if typ.IsVariadic() {
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return providerDescriptor{}, errors.Errorf("variadic function can't be used as a provider: %s", loc)
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}
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numIn := typ.NumIn()
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in := make([]providerInput, numIn)
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for i := 0; i < numIn; i++ {
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in[i] = providerInput{
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Type: typ.In(i),
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}
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}
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errIdx := -1
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numOut := typ.NumOut()
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var out []providerOutput
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for i := 0; i < numOut; i++ {
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t := typ.Out(i)
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if t == errType {
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if i != numOut-1 {
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return providerDescriptor{}, errors.Errorf("output error parameter is not last parameter in function %s", loc)
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}
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errIdx = i
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} else {
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out = append(out, providerOutput{Type: t})
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}
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}
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return providerDescriptor{
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Inputs: in,
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Outputs: out,
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Fn: func(values []reflect.Value) ([]reflect.Value, error) {
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res := val.Call(values)
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if errIdx >= 0 {
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err := res[errIdx]
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if !err.IsZero() {
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return nil, err.Interface().(error)
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}
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return res[0:errIdx], nil
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}
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return res, nil
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},
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Location: loc,
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}, nil
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}
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var errType = reflect.TypeOf((*error)(nil)).Elem()
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func postProcessProvider(descriptor providerDescriptor) (providerDescriptor, error) {
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descriptor, err := expandStructArgsProvider(descriptor)
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if err != nil {
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return providerDescriptor{}, err
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}
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err = checkInputAndOutputTypes(descriptor)
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return descriptor, err
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}
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func checkInputAndOutputTypes(descriptor providerDescriptor) error {
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for _, input := range descriptor.Inputs {
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err := isExportedType(input.Type)
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if err != nil {
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return err
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}
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}
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for _, output := range descriptor.Outputs {
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err := isExportedType(output.Type)
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if err != nil {
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return err
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}
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}
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return nil
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}
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