Add strictly typed input feature gate

confmap/confmap.go

@@ -16,6 +16,7 @@ import (
 	"github.com/knadh/koanf/providers/confmap"
 	"github.com/knadh/koanf/v2"
 
+	"go.opentelemetry.io/collector/confmap/internal"
 	encoder "go.opentelemetry.io/collector/confmap/internal/mapstructure"
 )
 
@@ -156,7 +157,7 @@ func decodeConfig(m *Conf, result any, errorUnused bool, skipTopLevelUnmarshaler
 		ErrorUnused:      errorUnused,
 		Result:           result,
 		TagName:          "mapstructure",
-		WeaklyTypedInput: true,
+		WeaklyTypedInput: !internal.StrictlyTypedInputGate.IsEnabled(),
 		MatchName:        caseSensitiveMatchName,
 		DecodeHook: mapstructure.ComposeDecodeHookFunc(
 			expandNilStructPointersHookFunc(),

confmap/expand.go

@@ -11,6 +11,8 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+
+	"go.opentelemetry.io/collector/confmap/internal"
 )
 
 // schemePattern defines the regexp pattern for scheme names.
@@ -111,22 +113,43 @@ func (mr *Resolver) findAndExpandURI(ctx context.Context, input string) (any, bo
 	if uri == input {
 		// If the value is a single URI, then the return value can be anything.
 		// This is the case `foo: ${file:some_extra_config.yml}`.
-		return mr.expandURI(ctx, input)
+		ret, ok, err := mr.expandURI(ctx, input)
+		if err != nil {
+			return input, false, err
+		}
+
+		raw, err := ret.AsRaw()
+		if err != nil {
+			return input, false, err
+		}
+
+		return raw, ok, nil
 	}
 	expanded, changed, err := mr.expandURI(ctx, uri)
 	if err != nil {
 		return input, false, err
 	}
-	repl, err := toString(expanded)
+
+	var repl string
+	if internal.StrictlyTypedInputGate.IsEnabled() {
+		repl, err = toStringStrictType(*expanded)
+	} else {
+		repl, err = toString(expanded)
+	}
 	if err != nil {
 		return input, false, fmt.Errorf("expanding %v: %w", uri, err)
 	}
 	return strings.ReplaceAll(input, uri, repl), changed, err
 }
 
 // toString attempts to convert input to a string.
-func toString(input any) (string, error) {
+func toString(ret *Retrieved) (string, error) {
 	// This list must be kept in sync with checkRawConfType.
+	input, err := ret.AsRaw()
+	if err != nil {
+		return "", err
+	}
+
 	val := reflect.ValueOf(input)
 	switch val.Kind() {
 	case reflect.String:
@@ -142,7 +165,27 @@ func toString(input any) (string, error) {
 	}
 }
 
-func (mr *Resolver) expandURI(ctx context.Context, input string) (any, bool, error) {
+func toStringStrictType(ret Retrieved) (string, error) {
+	input, err := ret.AsRaw()
+	if err != nil {
+		return "", err
+	}
+
+	str, ok := ret.getStringRepr()
+	if !ok {
+		return "", fmt.Errorf("expected convertable to string value type, got %v(%T)", input, input)
+	}
+
+	val := reflect.ValueOf(input)
+	switch val.Kind() {
+	case reflect.String, reflect.Int, reflect.Int32, reflect.Int64, reflect.Float32, reflect.Float64, reflect.Bool:
+		return str, nil
+	default:
+		return "", fmt.Errorf("expected convertable to string value type, got %q(%T)", input, input)
+	}
+}
+
+func (mr *Resolver) expandURI(ctx context.Context, input string) (*Retrieved, bool, error) {
 	// strip ${ and }
 	uri := input[2 : len(input)-1]
 
@@ -163,8 +206,7 @@ func (mr *Resolver) expandURI(ctx context.Context, input string) (any, bool, err
 		return nil, false, err
 	}
 	mr.closers = append(mr.closers, ret.Close)
-	val, err := ret.AsRaw()
-	return val, true, err
+	return ret, true, nil
 }
 
 type location struct {

confmap/go.mod

@@ -8,6 +8,7 @@ require (
 	github.com/knadh/koanf/providers/confmap v0.1.0
 	github.com/knadh/koanf/v2 v2.1.1
 	github.com/stretchr/testify v1.9.0
+	go.opentelemetry.io/collector/featuregate v1.9.0
 	go.uber.org/goleak v1.3.0
 	go.uber.org/multierr v1.11.0
 	go.uber.org/zap v1.27.0
@@ -16,6 +17,7 @@ require (
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/hashicorp/go-version v1.7.0 // indirect
 	github.com/mitchellh/copystructure v1.2.0 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
@@ -25,3 +27,5 @@ retract (
 	v0.76.0 // Depends on retracted pdata v1.0.0-rc10 module, use v0.76.1
 	v0.69.0 // Release failed, use v0.69.1
 )
+
+replace go.opentelemetry.io/collector/featuregate => ../featuregate

confmap/internal/e2e/go.mod

@@ -1,3 +1,4 @@
+<<<<<<< HEAD
 module go.opentelemetry.io/collector/confmap/internal/e2e
 
 go 1.21.0
@@ -28,3 +29,38 @@ replace go.opentelemetry.io/collector/confmap => ../../
 replace go.opentelemetry.io/collector/confmap/provider/fileprovider => ../../provider/fileprovider
 
 replace go.opentelemetry.io/collector/confmap/provider/envprovider => ../../provider/envprovider
+||||||| parent of 53be34094 ([chore] Add end to end tests for type casting)
+=======
+module go.opentelemetry.io/collector/confmap/internal/e2e
+
+go 1.21.0
+
+require (
+	github.com/stretchr/testify v1.9.0
+	go.opentelemetry.io/collector/confmap v0.102.1
+	go.opentelemetry.io/collector/confmap/provider/envprovider v0.102.1
+	go.opentelemetry.io/collector/confmap/provider/fileprovider v0.102.1
+	go.opentelemetry.io/collector/featuregate v1.9.0
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/go-viper/mapstructure/v2 v2.0.0 // indirect
+	github.com/hashicorp/go-version v1.7.0 // indirect
+	github.com/knadh/koanf/maps v0.1.1 // indirect
+	github.com/knadh/koanf/providers/confmap v0.1.0 // indirect
+	github.com/knadh/koanf/v2 v2.1.1 // indirect
+	github.com/mitchellh/copystructure v1.2.0 // indirect
+	github.com/mitchellh/reflectwalk v1.0.2 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
+	go.uber.org/zap v1.27.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
+
+replace go.opentelemetry.io/collector/confmap => ../../
+
+replace go.opentelemetry.io/collector/confmap/provider/fileprovider => ../../provider/fileprovider
+
+replace go.opentelemetry.io/collector/confmap/provider/envprovider => ../../provider/envprovider
+>>>>>>> 53be34094 ([chore] Add end to end tests for type casting)

confmap/internal/featuregate.go

@@ -0,0 +1,14 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package internal // import "go.opentelemetry.io/collector/confmap/internal"
+
+import "go.opentelemetry.io/collector/featuregate"
+
+const StrictlyTypedInputID = "confmap.strictlyTypedInput"
+
+var StrictlyTypedInputGate = featuregate.GlobalRegistry().MustRegister(StrictlyTypedInputID,
+	featuregate.StageAlpha,
+	featuregate.WithRegisterFromVersion("v0.103.0"),
+	featuregate.WithRegisterDescription("Makes type casting rules during configuration unmarshaling stricter. See https://github.com/open-telemetry/opentelemetry-collector/blob/main/docs/rfcs/env-vars.md for more details."),
+)

confmap/provider.go

@@ -99,10 +99,15 @@ type ChangeEvent struct {
 type Retrieved struct {
 	rawConf   any
 	closeFunc CloseFunc
+
+	stringRepresentation string
+	isSetString          bool
 }
 
 type retrievedSettings struct {
-	closeFunc CloseFunc
+	stringRepresentation string
+	isSetString          bool
+	closeFunc            CloseFunc
 }
 
 // RetrievedOption options to customize Retrieved values.
@@ -116,6 +121,13 @@ func WithRetrievedClose(closeFunc CloseFunc) RetrievedOption {
 	}
 }
 
+func WithStringRepresentation(stringRepresentation string) RetrievedOption {
+	return func(settings *retrievedSettings) {
+		settings.stringRepresentation = stringRepresentation
+		settings.isSetString = true
+	}
+}
+
 // NewRetrieved returns a new Retrieved instance that contains the data from the raw deserialized config.
 // The rawConf can be one of the following types:
 //   - Primitives: int, int32, int64, float32, float64, bool, string;
@@ -129,7 +141,12 @@ func NewRetrieved(rawConf any, opts ...RetrievedOption) (*Retrieved, error) {
 	for _, opt := range opts {
 		opt(&set)
 	}
-	return &Retrieved{rawConf: rawConf, closeFunc: set.closeFunc}, nil
+	return &Retrieved{
+		rawConf:              rawConf,
+		closeFunc:            set.closeFunc,
+		stringRepresentation: set.stringRepresentation,
+		isSetString:          set.isSetString,
+	}, nil
 }
 
 // AsConf returns the retrieved configuration parsed as a Conf.
@@ -152,6 +169,10 @@ func (r *Retrieved) AsRaw() (any, error) {
 	return r.rawConf, nil
 }
 
+func (r *Retrieved) getStringRepr() (string, bool) {
+	return r.stringRepresentation, r.isSetString
+}
+
 // Close and release any watchers that Provider.Retrieve may have created.
 //
 // Should block until all resources are closed, and guarantee that `onChange` is not

confmap/provider/internal/provider.go

@@ -17,5 +17,13 @@ func NewRetrievedFromYAML(yamlBytes []byte, opts ...confmap.RetrievedOption) (*c
 	if err := yaml.Unmarshal(yamlBytes, &rawConf); err != nil {
 		return nil, err
 	}
+
+	switch v := rawConf.(type) {
+	case string:
+		opts = append(opts, confmap.WithStringRepresentation(v))
+	default:
+		opts = append(opts, confmap.WithStringRepresentation(string(yamlBytes)))
+	}
+
 	return confmap.NewRetrieved(rawConf, opts...)
 }