fix: helmBinary setting ignored in multi-document YAML files (#2414)

* fix: helmBinary setting ignored in multi-document YAML files

The helmBinary setting in helmfile.yaml was being ignored when using
multi-document YAML files (files with --- separators).

Root Cause:
When processing multi-document YAML files, the load() function splits
the file into parts and processes each part separately. Each part was
calling applyDefaultsAndOverrides() which would set an empty helmBinary
to the default 'helm'. When merging parts, the default value from a
later part would override the correct value from an earlier part.

Fix:
- Added a new applyDefaults parameter to ParseAndLoad() to control when
  defaults are applied
- Modified rawLoad() to pass applyDefaults=false when processing
  individual parts
- Added a call to ApplyDefaultsAndOverrides() after all parts are merged
  to apply defaults once on the final merged state
- Exported ApplyDefaultsAndOverrides() method for use by the app package

Fixes: #2319
Signed-off-by: yxxhero <aiopsclub@163.com>

* fix: update comment per PR review

Change 're-apply' to 'apply' since defaults are never applied during
part processing (applyDefaults=false is passed), so this is the first
and only time defaults are applied to the merged state.

Signed-off-by: yxxhero <aiopsclub@163.com>

* fix: clarify applyDefaults logic in test LoadFile callbacks

Add explicit applyDefaults variable with comment explaining why it
equals evaluateBases: base files shouldn't apply defaults, only the
main file should after all parts/bases are merged.

Signed-off-by: yxxhero <aiopsclub@163.com>

* fix: address PR review comments

- Remove applyDefaults parameter from rawLoad() since it's always false
- Add regression test for multi-document YAML with helmBinary (issue #2319)

Signed-off-by: yxxhero <aiopsclub@163.com>

* test: add integration test for helmBinary in multi-document YAML

Add TestHelmBinaryPreservedInMultiDocumentYAML that exercises the full
loadDesiredStateFromYaml path to ensure helmBinary from the first
document is preserved when merging multi-document YAML files.

This is a regression test at the load() orchestration level for issue #2319.

Signed-off-by: yxxhero <aiopsclub@163.com>

---------

Signed-off-by: yxxhero <aiopsclub@163.com>

pkg/state/create.go

@@ -137,6 +137,12 @@ func (c *StateCreator) Parse(content []byte, baseDir, file string) (*HelmState,
 	return &state, nil
 }
 
+// ApplyDefaultsAndOverrides applies default binary paths and command-line overrides.
+// This is an exported version of applyDefaultsAndOverrides for use by the app package.
+func (c *StateCreator) ApplyDefaultsAndOverrides(state *HelmState) {
+	c.applyDefaultsAndOverrides(state)
+}
+
 // applyDefaultsAndOverrides applies default binary paths and command-line overrides
 func (c *StateCreator) applyDefaultsAndOverrides(state *HelmState) {
 	if c.overrideHelmBinary != "" && c.overrideHelmBinary != DefaultHelmBinary {
@@ -179,7 +185,8 @@ func (c *StateCreator) LoadEnvValues(target *HelmState, env string, failOnMissin
 
 // Parses YAML into HelmState, while loading environment values files relative to the `baseDir`
 // evaluateBases=true means that this is NOT a base helmfile
-func (c *StateCreator) ParseAndLoad(content []byte, baseDir, file string, envName string, failOnMissingEnv, evaluateBases bool, envValues, overrode *environment.Environment) (*HelmState, error) {
+// applyDefaults=true means that applyDefaultsAndOverrides should be called
+func (c *StateCreator) ParseAndLoad(content []byte, baseDir, file string, envName string, failOnMissingEnv, evaluateBases, applyDefaults bool, envValues, overrode *environment.Environment) (*HelmState, error) {
 	state, err := c.Parse(content, baseDir, file)
 	if err != nil {
 		return nil, err
@@ -198,7 +205,9 @@ func (c *StateCreator) ParseAndLoad(content []byte, baseDir, file string, envNam
 		// Apply default binaries and command-line overrides only for the main helmfile
 		// after loading and merging all bases. This ensures that values from bases are
 		// properly respected and that later bases/documents can override earlier ones.
-		c.applyDefaultsAndOverrides(state)
+		if applyDefaults {
+			c.applyDefaultsAndOverrides(state)
+		}
 	}
 
 	state, err = c.LoadEnvValues(state, envName, failOnMissingEnv, envValues, overrode)