fix(chart/v3): keep yaml numbers as json.Number

Port the UseNumber decode path into charts v3 so integers survive
toYaml and toToml. v2 charts keep float64 for compatibility.

Fixes #30901

Signed-off-by: Arjun Vijay Prakash <arjunv.prakash12345@gmail.com>

internal/chart/v3/loader/load.go

@@ -19,6 +19,7 @@ package loader
 import (
 	"bufio"
 	"bytes"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -206,7 +207,12 @@ func LoadValues(data io.Reader) (map[string]any, error) {
 			}
 			return nil, fmt.Errorf("error reading yaml document: %w", err)
 		}
-		if err := yaml.Unmarshal(raw, &currentMap); err != nil {
+		// Decode numbers as json.Number so integers stay integers through
+		// toYaml/toToml. v2 charts keep float64 for compatibility; see #30884.
+		if err := yaml.Unmarshal(raw, &currentMap, func(d *json.Decoder) *json.Decoder {
+			d.UseNumber()
+			return d
+		}); err != nil {
 			return nil, fmt.Errorf("cannot unmarshal yaml document: %w", err)
 		}
 		values = MergeMaps(values, currentMap)

internal/chart/v3/loader/load_test.go

@@ -20,6 +20,7 @@ import (
 	"archive/tar"
 	"bytes"
 	"compress/gzip"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -31,8 +32,10 @@ import (
 	"testing"
 	"time"
 
+	"github.com/BurntSushi/toml"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"sigs.k8s.io/yaml"
 
 	chart "helm.sh/helm/v4/internal/chart/v3"
 	"helm.sh/helm/v4/pkg/chart/common"
@@ -420,6 +423,43 @@ foo:
 				},
 			},
 		},
+		"It should load integers as json.Number": {
+			data: []byte(`
+key: 13
+`),
+			expctedValues: map[string]any{
+				"key": json.Number("13"),
+			},
+		},
+		"It should load floats as json.Number": {
+			data: []byte(`
+pi: 3.14
+`),
+			expctedValues: map[string]any{
+				"pi": json.Number("3.14"),
+			},
+		},
+		"It should keep integers larger than float64 mantissa as json.Number": {
+			data: []byte(`
+key: 9007199254740993
+`),
+			expctedValues: map[string]any{
+				"key": json.Number("9007199254740993"),
+			},
+		},
+		"It should load nested numbers as json.Number": {
+			data: []byte(`
+global:
+  key: 13
+  ratio: 1.5
+`),
+			expctedValues: map[string]any{
+				"global": map[string]any{
+					"key":   json.Number("13"),
+					"ratio": json.Number("1.5"),
+				},
+			},
+		},
 	}
 	for testName, testCase := range testCases {
 		t.Run(testName, func(tt *testing.T) {
@@ -430,6 +470,33 @@ foo:
 	}
 }
 
+func TestLoadValuesNumberEncoding(t *testing.T) {
+	values, err := LoadValues(bytes.NewReader([]byte(`
+global:
+  key: 13
+  large: 9007199254740993
+  pi: 3.14
+`)))
+	require.NoError(t, err)
+
+	yamlOut, err := yaml.Marshal(values)
+	require.NoError(t, err)
+	assert.Contains(t, string(yamlOut), "key: 13")
+	assert.Contains(t, string(yamlOut), "large: 9007199254740993")
+	assert.Contains(t, string(yamlOut), "pi: 3.14")
+	assert.NotContains(t, string(yamlOut), "13.0")
+	assert.NotContains(t, string(yamlOut), "1.048576e+")
+
+	var tomlBuf bytes.Buffer
+	require.NoError(t, toml.NewEncoder(&tomlBuf).Encode(values))
+	tomlOut := tomlBuf.String()
+	assert.Contains(t, tomlOut, "key = 13")
+	assert.Contains(t, tomlOut, "large = 9007199254740993")
+	assert.Contains(t, tomlOut, "pi = 3.14")
+	assert.NotContains(t, tomlOut, "13.0")
+	assert.NotContains(t, tomlOut, "key = \"13\"")
+}
+
 func TestLoadValuesEOFBoundary(t *testing.T) {
 	// Reproduces #32506: a single logical line whose length is a multiple of
 	// bufio's default buffer (4096) and has no trailing newline used to be

internal/chart/v3/util/dependencies_test.go

@@ -15,6 +15,7 @@ limitations under the License.
 package util
 
 import (
+	"encoding/json"
 	"os"
 	"path/filepath"
 	"sort"
@@ -219,6 +220,8 @@ func TestProcessDependencyImportValues(t *testing.T) {
 		case bool:
 			b := strconv.FormatBool(pv)
 			assert.Equalf(t, vv, b, "failed to match imported bool value %v with expected %v for key %q", b, vv, kk)
+		case json.Number:
+			assert.Equalf(t, vv, pv.String(), "failed to match imported number value %q with expected %q for key %q", pv, vv, kk)
 		default:
 			assert.Equalf(t, vv, pv, "failed to match imported string value %q with expected %q for key %q", pv, vv, kk)
 		}
@@ -296,6 +299,8 @@ func TestProcessDependencyImportValuesMultiLevelPrecedence(t *testing.T) {
 		case float64:
 			s := strconv.FormatFloat(pv, 'f', -1, 64)
 			assert.Equalf(t, vv, s, "failed to match imported float value %v with expected %v", s, vv)
+		case json.Number:
+			assert.Equalf(t, vv, pv.String(), "failed to match imported number value %q with expected %q", pv, vv)
 		default:
 			assert.Equalf(t, vv, pv, "failed to match imported string value %q with expected %q", pv, vv)
 		}

pkg/engine/funcs_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package engine
 
 import (
+	"encoding/json"
 	"math"
 	"strings"
 	"testing"
@@ -36,6 +37,22 @@ func TestFuncs(t *testing.T) {
 		tpl:    `{{ toYaml . }}`,
 		expect: `foo: bar`,
 		vars:   map[string]any{"foo": "bar"},
+	}, {
+		tpl:    `{{ toYaml . }}`,
+		expect: "key: 13",
+		vars:   map[string]any{"key": json.Number("13")},
+	}, {
+		tpl:    `{{ toYaml . }}`,
+		expect: "large: 9007199254740993",
+		vars:   map[string]any{"large": json.Number("9007199254740993")},
+	}, {
+		tpl:    `{{ toYaml . }}`,
+		expect: "pi: 3.14",
+		vars:   map[string]any{"pi": json.Number("3.14")},
+	}, {
+		tpl:    `{{ toToml . }}`,
+		expect: "key = 13\n",
+		vars:   map[string]any{"key": json.Number("13")},
 	}, {
 		tpl:    `{{ toYamlPretty . }}`,
 		expect: "baz:\n  - 1\n  - 2\n  - 3",