[chore] Add end to end tests for type casting (#10399)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

<!-- Issue number if applicable -->

Adds tests of current type casting behavior when using env and file
provider.

#### Link to tracking issue

Relates to #9854, #8565, #9532

confmap/internal/e2e/Makefile

@@ -0,0 +1 @@
+include ../../../Makefile.Common

confmap/internal/e2e/go.mod

@@ -0,0 +1,30 @@
+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
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/go-viper/mapstructure/v2 v2.0.0 // 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

confmap/internal/e2e/testdata/types_expand.yaml

@@ -0,0 +1 @@
+field: ${env:ENV}

confmap/internal/e2e/testdata/types_expand_inline.yaml

@@ -0,0 +1 @@
+field: "inline field with ${env:ENV} expansion"

confmap/internal/e2e/types_test.go

@@ -0,0 +1,168 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package e2etest
+
+import (
+	"context"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/collector/confmap"
+	"go.opentelemetry.io/collector/confmap/provider/envprovider"
+	"go.opentelemetry.io/collector/confmap/provider/fileprovider"
+)
+
+type TargetField string
+
+const (
+	TargetFieldInt          TargetField = "int_field"
+	TargetFieldString       TargetField = "string_field"
+	TargetFieldBool         TargetField = "bool_field"
+	TargetFieldInlineString TargetField = "inline_string_field"
+)
+
+type Test struct {
+	value       string
+	targetField TargetField
+	expected    any
+	expectedErr string
+}
+
+type TargetConfig[T any] struct {
+	Field T `mapstructure:"field"`
+}
+
+func AssertExpectedMatch[T any](t *testing.T, tt Test, conf *confmap.Conf, cfg *TargetConfig[T]) {
+	err := conf.Unmarshal(cfg)
+	if tt.expectedErr != "" {
+		require.ErrorContains(t, err, tt.expectedErr)
+		return
+	}
+	require.NoError(t, err)
+	require.Equal(t, tt.expected, cfg.Field)
+}
+
+func TestTypeCasting(t *testing.T) {
+	values := []Test{
+		{
+			value:       "123",
+			targetField: TargetFieldInt,
+			expected:    123,
+		},
+		{
+			value:       "123",
+			targetField: TargetFieldString,
+			expected:    "123",
+		},
+		{
+			value:       "123",
+			targetField: TargetFieldInlineString,
+			expected:    "inline field with 123 expansion",
+		},
+		{
+			value:       "0123",
+			targetField: TargetFieldInt,
+			expected:    83,
+		},
+		{
+			value:       "0123",
+			targetField: TargetFieldString,
+			expected:    "83",
+		},
+		{
+			value:       "0123",
+			targetField: TargetFieldInlineString,
+			expected:    "inline field with 83 expansion",
+		},
+		{
+			value:       "0xdeadbeef",
+			targetField: TargetFieldInt,
+			expected:    3735928559,
+		},
+		{
+			value:       "0xdeadbeef",
+			targetField: TargetFieldString,
+			expected:    "3735928559",
+		},
+		{
+			value:       "0xdeadbeef",
+			targetField: TargetFieldInlineString,
+			expected:    "inline field with 3735928559 expansion",
+		},
+		{
+			value:       "\"0123\"",
+			targetField: TargetFieldString,
+			expected:    "0123",
+		},
+		{
+			value:       "\"0123\"",
+			targetField: TargetFieldInt,
+			expected:    83,
+		},
+		{
+			value:       "\"0123\"",
+			targetField: TargetFieldInlineString,
+			expected:    "inline field with 0123 expansion",
+		},
+		{
+			value:       "!!str 0123",
+			targetField: TargetFieldString,
+			expected:    "0123",
+		},
+		{
+			value:       "!!str 0123",
+			targetField: TargetFieldInlineString,
+			expected:    "inline field with 0123 expansion",
+		},
+		{
+			value:       "t",
+			targetField: TargetFieldBool,
+			expected:    true,
+		},
+		{
+			value:       "23",
+			targetField: TargetFieldBool,
+			expected:    true,
+		},
+	}
+
+	for _, tt := range values {
+		t.Run(tt.value+"/"+string(tt.targetField), func(t *testing.T) {
+			testFile := "types_expand.yaml"
+			if tt.targetField == TargetFieldInlineString {
+				testFile = "types_expand_inline.yaml"
+			}
+
+			resolver, err := confmap.NewResolver(confmap.ResolverSettings{
+				URIs: []string{filepath.Join("testdata", testFile)},
+				ProviderFactories: []confmap.ProviderFactory{
+					fileprovider.NewFactory(),
+					envprovider.NewFactory(),
+				},
+			})
+			require.NoError(t, err)
+			t.Setenv("ENV", tt.value)
+
+			conf, err := resolver.Resolve(context.Background())
+			require.NoError(t, err)
+
+			switch tt.targetField {
+			case TargetFieldInt:
+				var cfg TargetConfig[int]
+				AssertExpectedMatch(t, tt, conf, &cfg)
+			case TargetFieldString, TargetFieldInlineString:
+				var cfg TargetConfig[string]
+				AssertExpectedMatch(t, tt, conf, &cfg)
+			case TargetFieldBool:
+				var cfg TargetConfig[bool]
+				AssertExpectedMatch(t, tt, conf, &cfg)
+			default:
+				t.Fatalf("unexpected target field %q", tt.targetField)
+			}
+
+		})
+	}
+}

versions.yaml

@@ -62,3 +62,4 @@ excluded-modules:
   - go.opentelemetry.io/collector/cmd/otelcorecol
   - go.opentelemetry.io/collector/internal/e2e
   - go.opentelemetry.io/collector/internal/tools
+  - go.opentelemetry.io/collector/confmap/internal/e2e