fix: compute mergedReleaseTemplateData lazily in PrepareChartify

Agent-Logs-Url: https://github.com/helmfile/helmfile/sessions/100b7974-3268-4dc8-be21-12bd82aa2dbb

Co-authored-by: yxxhero <11087727+yxxhero@users.noreply.github.com>

pkg/state/create_test.go

@@ -1324,7 +1324,7 @@ host: {{ .Values.ingress.host }}
 	generatedFiles, err := st.generateTemporaryReleaseValuesFilesWithData(
 		release,
 		[]any{"patch.yaml.gotmpl"},
-		tmplData,
+		func() (releaseTemplateData, error) { return tmplData, nil },
 	)
 	require.NoError(t, err)
 	require.Len(t, generatedFiles, 1)
@@ -1354,7 +1354,7 @@ func TestGenerateTemporaryReleaseValuesFilesWithData_InlineMap(t *testing.T) {
 	generatedFiles, err := st.generateTemporaryReleaseValuesFilesWithData(
 		release,
 		[]any{inlineValues},
-		tmplData,
+		func() (releaseTemplateData, error) { return tmplData, nil },
 	)
 	require.NoError(t, err)
 	require.Len(t, generatedFiles, 1)
@@ -1376,7 +1376,7 @@ func TestGenerateTemporaryReleaseValuesFilesWithData_UnknownTypeError(t *testing
 	_, err := st.generateTemporaryReleaseValuesFilesWithData(
 		release,
 		[]any{42},
-		tmplData,
+		func() (releaseTemplateData, error) { return tmplData, nil },
 	)
 	require.Error(t, err)
 	assert.Contains(t, err.Error(), "unexpected type of value")

pkg/state/helmx.go

@@ -404,18 +404,28 @@ func (st *HelmState) PrepareChartify(helm helmexec.Interface, release *ReleaseSp
 		shouldRun = true
 	}
 
-	var patchTemplateData *releaseTemplateData
-	if len(release.JSONPatches) > 0 || len(release.StrategicMergePatches) > 0 || len(release.Transformers) > 0 {
-		td, err := st.mergedReleaseTemplateData(release)
-		if err != nil {
-			return nil, clean, fmt.Errorf("failed to compute merged release values for patch rendering: %v", err)
+	// patchTemplateData is computed lazily on first use: only when an actual string patch/transformer
+	// file path is rendered. Inline-map entries don't require template data at all, so we avoid
+	// unnecessary I/O for releases whose patches are all inline maps or that have no string entries.
+	var (
+		cachedPatchTemplateData    releaseTemplateData
+		cachedPatchTemplateDataErr error
+		cachedPatchTemplateDataSet bool
+	)
+	getPatchTemplateData := func() (releaseTemplateData, error) {
+		if !cachedPatchTemplateDataSet {
+			cachedPatchTemplateDataSet = true
+			cachedPatchTemplateData, cachedPatchTemplateDataErr = st.mergedReleaseTemplateData(release)
+			if cachedPatchTemplateDataErr != nil {
+				cachedPatchTemplateDataErr = fmt.Errorf("failed to compute merged release values for patch rendering: %v", cachedPatchTemplateDataErr)
+			}
 		}
-		patchTemplateData = &td
+		return cachedPatchTemplateData, cachedPatchTemplateDataErr
 	}
 
 	jsonPatches := release.JSONPatches
 	if len(jsonPatches) > 0 {
-		generatedFiles, err := st.generateTemporaryReleaseValuesFilesWithData(release, jsonPatches, *patchTemplateData)
+		generatedFiles, err := st.generateTemporaryReleaseValuesFilesWithData(release, jsonPatches, getPatchTemplateData)
 		if err != nil {
 			return nil, clean, err
 		}
@@ -429,7 +439,7 @@ func (st *HelmState) PrepareChartify(helm helmexec.Interface, release *ReleaseSp
 
 	strategicMergePatches := release.StrategicMergePatches
 	if len(strategicMergePatches) > 0 {
-		generatedFiles, err := st.generateTemporaryReleaseValuesFilesWithData(release, strategicMergePatches, *patchTemplateData)
+		generatedFiles, err := st.generateTemporaryReleaseValuesFilesWithData(release, strategicMergePatches, getPatchTemplateData)
 		if err != nil {
 			return nil, clean, err
 		}
@@ -443,7 +453,7 @@ func (st *HelmState) PrepareChartify(helm helmexec.Interface, release *ReleaseSp
 
 	transformers := release.Transformers
 	if len(transformers) > 0 {
-		generatedFiles, err := st.generateTemporaryReleaseValuesFilesWithData(release, transformers, *patchTemplateData)
+		generatedFiles, err := st.generateTemporaryReleaseValuesFilesWithData(release, transformers, getPatchTemplateData)
 		if err != nil {
 			return nil, clean, err
 		}

pkg/state/state.go

@@ -4034,8 +4034,12 @@ func (st *HelmState) renderValuesFileToBytesWithData(path string, templateData r
 	return rawBytes, nil
 }
 
-func (st *HelmState) generateTemporaryReleaseValuesFilesWithData(release *ReleaseSpec, values []any, templateData releaseTemplateData) ([]string, error) {
+func (st *HelmState) generateTemporaryReleaseValuesFilesWithData(release *ReleaseSpec, values []any, getTemplateData func() (releaseTemplateData, error)) ([]string, error) {
 	return st.generateTemporaryReleaseValuesFilesCore(release, values, func(path string) ([]byte, error) {
+		templateData, err := getTemplateData()
+		if err != nil {
+			return nil, err
+		}
 		return st.renderValuesFileToBytesWithData(path, templateData)
 	})
 }