fix!: hide struct binding behind a feature flag

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

.github/workflows/ci.yaml

@@ -24,9 +24,9 @@ jobs:
         uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
 
       - name: Set up Go
-        uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5.0.0
         with:
-          go-version: '1.21'
+          go-version: "1.21"
 
       - name: Build
         run: go build .
@@ -44,15 +44,15 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        go: ['1.19', '1.20', '1.21']
-        tags: ['', 'finder']
+        go: ["1.19", "1.20", "1.21"]
+        tags: ["", "finder", "viper_bind_struct"]
 
     steps:
       - name: Checkout repository
         uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
 
       - name: Set up Go
-        uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5.0.0
         with:
           go-version: ${{ matrix.go }}
 
@@ -73,9 +73,9 @@ jobs:
         uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
 
       - name: Set up Go
-        uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0
+        uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491 # v5.0.0
         with:
-          go-version: '1.21'
+          go-version: "1.21"
 
       - name: Lint
         uses: golangci/golangci-lint-action@3a919529898de77ec3da873e3063ca4b10e7f5cc # v3.7.0

.github/workflows/codeql-analysis.yaml

@@ -43,7 +43,7 @@ jobs:
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@407ffafae6a767df3e0230c3df91b6443ae8df75 # v2.22.8
+      uses: github/codeql-action/init@c0d1daa7f7e14667747d73a7dbbe8c074bc8bfe2 # v2.22.9
       with:
         languages: ${{ matrix.language }}
         # If you wish to specify custom queries, you can do so here or in a config file.
@@ -54,7 +54,7 @@ jobs:
     # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
     # If this step fails, then you should remove it and run the build manually (see below)
     - name: Autobuild
-      uses: github/codeql-action/autobuild@407ffafae6a767df3e0230c3df91b6443ae8df75 # v2.22.8
+      uses: github/codeql-action/autobuild@c0d1daa7f7e14667747d73a7dbbe8c074bc8bfe2 # v2.22.9
 
     # ℹ️ Command-line programs to run using the OS shell.
     # 📚 https://git.io/JvXDl
@@ -68,5 +68,5 @@ jobs:
     #   make release
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@407ffafae6a767df3e0230c3df91b6443ae8df75 # v2.22.8
+      uses: github/codeql-action/analyze@c0d1daa7f7e14667747d73a7dbbe8c074bc8bfe2 # v2.22.9
 

internal/features/bind_struct.go

@@ -0,0 +1,5 @@
+//go:build viper_bind_struct
+
+package features
+
+const BindStruct = true

internal/features/bind_struct_default.go

@@ -0,0 +1,5 @@
+//go:build !viper_bind_struct
+
+package features
+
+const BindStruct = false

viper.go

@@ -48,6 +48,7 @@ import (
 	"github.com/spf13/viper/internal/encoding/json"
 	"github.com/spf13/viper/internal/encoding/toml"
 	"github.com/spf13/viper/internal/encoding/yaml"
+	"github.com/spf13/viper/internal/features"
 )
 
 // ConfigMarshalError happens when failing to marshal the configuration.
@@ -1114,14 +1115,20 @@ func Unmarshal(rawVal any, opts ...DecoderConfigOption) error {
 }
 
 func (v *Viper) Unmarshal(rawVal any, opts ...DecoderConfigOption) error {
-	// TODO: make this optional?
-	structKeys, err := v.decodeStructKeys(rawVal, opts...)
-	if err != nil {
-		return err
+	keys := v.AllKeys()
+
+	if features.BindStruct {
+		// TODO: make this optional?
+		structKeys, err := v.decodeStructKeys(rawVal, opts...)
+		if err != nil {
+			return err
+		}
+
+		keys = append(keys, structKeys...)
 	}
 
 	// TODO: struct keys should be enough?
-	return decode(v.getSettings(append(v.AllKeys(), structKeys...)), defaultDecoderConfig(rawVal, opts...))
+	return decode(v.getSettings(keys), defaultDecoderConfig(rawVal, opts...))
 }
 
 func (v *Viper) decodeStructKeys(input any, opts ...DecoderConfigOption) ([]string, error) {
@@ -1179,7 +1186,20 @@ func (v *Viper) UnmarshalExact(rawVal any, opts ...DecoderConfigOption) error {
 	config := defaultDecoderConfig(rawVal, opts...)
 	config.ErrorUnused = true
 
-	return decode(v.AllSettings(), config)
+	keys := v.AllKeys()
+
+	if features.BindStruct {
+		// TODO: make this optional?
+		structKeys, err := v.decodeStructKeys(rawVal, opts...)
+		if err != nil {
+			return err
+		}
+
+		keys = append(keys, structKeys...)
+	}
+
+	// TODO: struct keys should be enough?
+	return decode(v.getSettings(keys), config)
 }
 
 // BindPFlags binds a full flag set to the configuration, using each flag's long

viper_test.go

@@ -28,6 +28,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"github.com/spf13/viper/internal/features"
 	"github.com/spf13/viper/internal/testutil"
 )
 
@@ -956,6 +957,10 @@ func TestUnmarshalWithDecoderOptions(t *testing.T) {
 }
 
 func TestUnmarshalWithAutomaticEnv(t *testing.T) {
+	if !features.BindStruct {
+		t.Skip("binding struct is not enabled")
+	}
+
 	t.Setenv("PORT", "1313")
 	t.Setenv("NAME", "Steve")
 	t.Setenv("DURATION", "1s1ms")
@@ -1052,6 +1057,32 @@ func TestUnmarshalWithAutomaticEnv(t *testing.T) {
 
 		assert.Error(t, err, "expected viper.Unmarshal to return error due to unset field 'FLAG'")
 	})
+
+	t.Run("Exact", func(t *testing.T) {
+		var config Configuration
+
+		v.Set("port", 1234)
+		if err := v.UnmarshalExact(&config); err != nil {
+			t.Fatalf("unable to decode into struct, %v", err)
+		}
+
+		assert.Equal(
+			t,
+			Configuration{
+				Name:     "Steve",
+				Port:     1234,
+				Duration: time.Second + time.Millisecond,
+				Modes:    []int{1, 2, 3},
+				Authentication: AuthConfig{
+					Secret: "42",
+				},
+				Storage: StorageConfig{
+					Size: 4096,
+				},
+			},
+			config,
+		)
+	})
 }
 
 func TestBindPFlags(t *testing.T) {