* feat(state): add mergeStrategy field to EnvironmentSpec
Introduces a per-environment mergeStrategy with valid values "override"
(default, current behavior) and "fallback". This commit only adds the
field, the constants, and a parse-time validator; the loader still
ignores the value, so behavior is unchanged.
Subsequent commits thread the value through the values loader and
implement the fallback semantics.
Signed-off-by: Dominik Schmidt <dev@dominik-schmidt.de>
* refactor(state): thread mergeStrategy through values loader
Adds a mergeStrategy string parameter to LoadEnvironmentValues,
loadValuesEntries, and mapMerge so the value can flow from
EnvironmentSpec down to the merge call site. Behavior is unchanged in
this commit; mapMerge ignores the strategy and the next commit
implements the fallback semantics.
Top-level state.DefaultValues and the --state-values-file/-set loaders
are passed an empty strategy ("") since they have no per-environment
spec to consult and stay on the default override behavior.
Signed-off-by: Dominik Schmidt <dev@dominik-schmidt.de>
* feat(state): implement fallback merge strategy
Adds a hand-rolled fallbackDeepMerge that, unlike mergo, preserves
keys present in the destination even when their value is the zero
value (false, 0, "", nil, empty list/map). mapMerge dispatches to it
when mergeStrategy == "fallback"; "override" and the empty default
keep using mergo with WithOverride so existing behaviour is unchanged.
Validation lives at the entry of LoadEnvironmentValues so a single
chokepoint guards the field. Invalid values produce an error naming
both the offending value and the valid options.
Tests cover: first-file-wins precedence, gap filling, deep nested
merge, three-file chains, explicit zero-value preservation (the case
naïve mergo gets wrong), explicit nil preservation, inline map
entries, override regression, default-equals-override equivalence,
and invalid-strategy errors.
Signed-off-by: Dominik Schmidt <dev@dominik-schmidt.de>
* feat(state): expose prior-file values in fallback template context
Under mergeStrategy: fallback, .gotmpl values files can now reference
values from earlier files in the same `values:` list via .Values
(e.g. `service.domain: "service.{{ .Values.cluster.domain }}"`).
The accumulated result is layered under env.GetMergedValues so env
defaults, env values, and CLI overrides still win on overlap. Override
mode keeps the historical template context — unchanged — so this is
strictly opt-in via the mergeStrategy field.
Together with the precedence flip from the previous commit, this lets
users replace the brittle two-stage `merged-values.yaml.gotmpl`
workaround with native helmfile syntax.
Tests cover the headline cross-file template reference case and pin
the override-mode contract that prior-file values stay invisible.
Signed-off-by: Dominik Schmidt <dev@dominik-schmidt.de>
* docs: document mergeStrategy and fallback semantics
Adds a new section to values-and-merging.md describing the override vs
fallback strategies, the explicit-zero-value preservation guarantee,
and the cross-file template reference behavior. Adds a brief pointer
to environments.md so users land on the new field from the
environment values discussion.
Signed-off-by: Dominik Schmidt <dev@dominik-schmidt.de>
* refactor(state): reuse maputil.MergeMaps for fallback merge
Replaces the hand-rolled fallbackDeepMerge with a single call to
maputil.MergeMaps, swapping its arguments so the accumulated dest wins
over the new src file. Same first-file-wins semantic, fewer lines, and
the fallback path now inherits the same slice merge strategies the
rest of helmfile already uses.
The one observable behavior shift is for explicit nil values: under
fallback, nil in an earlier file no longer 'wins' over a non-nil value
in a later file — instead it falls through (matching MergeMaps' rule
that nil from the override side only fills missing keys). This is
internally consistent: nil-overwrites is an mergo.WithOverride quirk
that lives only in the override path. The renamed test
NilFallsThroughToFallback pins the new behavior with a comment
referencing the contrast with override mode (Issue1154).
Signed-off-by: Dominik Schmidt <dev@dominik-schmidt.de>
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Signed-off-by: Dominik Schmidt <dev@dominik-schmidt.de>
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