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allow ignore_changes to reference any map key
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There are situations when a user may want to keep or exclude a map key
using `ignore_changes` which may not be listed directly in the
configuration. This didn't work previously because the transformation
always started off with the configuration, and would never encounter a
key if it was only present in the prior value.
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@jbardin
jbardin committed Sep 29, 2020
1 parent a78d75c commit 87f7c05
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Showing 2 changed files with 268 additions and 26 deletions.
136 changes: 110 additions & 26 deletions terraform/eval_diff.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -607,38 +607,122 @@ func processIgnoreChangesIndividual(prior, config cty.Value, ignoreChanges []hcl
ignoreChangesPath[i] = path
}

var diags tfdiags.Diagnostics
ret, _ := cty.Transform(config, func(path cty.Path, v cty.Value) (cty.Value, error) {
// First we must see if this is a path that's being ignored at all.
// We're looking for an exact match here because this walk will visit
// leaf values first and then their containers, and we want to do
// the "ignore" transform once we reach the point indicated, throwing
// away any deeper values we already produced at that point.
var ignoreTraversal hcl.Traversal
for i, candidate := range ignoreChangesPath {
if path.Equals(candidate) {
ignoreTraversal = ignoreChanges[i]
type ignoreChange struct {
// Path is the full path, minus any trailing map index
path cty.Path
// Value is the value we are to retain at the above path. If there is a
// key value, this must be a map and the desired value will be at the
// key index.
value cty.Value
// Key is the index key if the ignored path ends in a map index.
key cty.Value
}
var ignoredValues []ignoreChange

// Find the actual changes first and store them in the ignoreChange struct.
// If the change was to a map value, and the key doesn't exist in the
// config, it would never be visited in the transform walk.
for _, icPath := range ignoreChangesPath {
key := cty.NullVal(cty.String)
// check for a map index, since maps are the only structure where we
// could have invalid path steps.
last, ok := icPath[len(icPath)-1].(cty.IndexStep)
if ok {
if last.Key.Type() == cty.String {
icPath = icPath[:len(icPath)-1]
key = last.Key
}
}
if ignoreTraversal == nil {
return v, nil

// The structure should have been validated already, and we already
// trimmed the trailing map index. Any other intermediate index error
// means we wouldn't be able to apply the value below, so no need to
// record this.
p, err := icPath.Apply(prior)
if err != nil {
continue
}
c, err := icPath.Apply(config)
if err != nil {
continue
}

// If we're able to follow the same path through the prior value,
// we'll take the value there instead, effectively undoing the
// change that was planned.
priorV, diags := hcl.ApplyPath(prior, path, nil)
if diags.HasErrors() {
// We just ignore the errors and move on here, since we assume it's
// just because the prior value was a slightly-different shape.
// It could potentially also be that the traversal doesn't match
// the schema, but we should've caught that during the validate
// walk if so.
return v, nil
eq := p.Equals(c)
if eq.IsKnown() && eq.False() {
// there a change to ignore at this path, store the prior value
ignoredValues = append(ignoredValues, ignoreChange{icPath, p, key})
}
}

if len(ignoredValues) == 0 {
return config, nil
}

ret, _ := cty.Transform(config, func(path cty.Path, v cty.Value) (cty.Value, error) {
for _, ignored := range ignoredValues {
if !path.Equals(ignored.path) {
return v, nil
}

// no index, so we can return the entire value
if ignored.key.IsNull() {
return ignored.value, nil
}

// we have an index key, so make sure we have a map
if !v.Type().IsMapType() {
// we'll let other validation catch any type mismatch
return v, nil
}

// Now we know we are ignoring a specific index of this map, so get
// the config map and modify, add, or remove the desired key.
var configMap map[string]cty.Value
var priorMap map[string]cty.Value

if !v.IsNull() {
if !v.IsKnown() {
// if the entire map is not known, we can't ignore any
// specific keys yet.
continue
}
configMap = v.AsValueMap()
}
if configMap == nil {
configMap = map[string]cty.Value{}
}

// We also need to create a prior map, so we can check for
// existence while getting the value. Value.Index will always
// return null.
if !ignored.value.IsNull() {
priorMap = ignored.value.AsValueMap()
}
if priorMap == nil {
priorMap = map[string]cty.Value{}
}

key := ignored.key.AsString()
priorElem, keep := priorMap[key]

switch {
case !keep:
// this didn't exist in the old map value, so we're keeping the
// "absence" of the key by removing it from the config
delete(configMap, key)
default:
configMap[key] = priorElem
}

if len(configMap) == 0 {
return cty.MapValEmpty(v.Type().ElementType()), nil
}

return cty.MapVal(configMap), nil
}
return priorV, nil
return v, nil
})
return ret, diags
return ret, nil
}

// a group of key-*ResourceAttrDiff pairs from the same flatmapped container
Expand Down
158 changes: 158 additions & 0 deletions terraform/eval_diff_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,164 @@ func TestProcessIgnoreChangesIndividual(t *testing.T) {
"b": cty.StringVal("new b value"),
}),
},
"list_index": {
cty.ObjectVal(map[string]cty.Value{
"a": cty.ListVal([]cty.Value{
cty.StringVal("a0 value"),
cty.StringVal("a1 value"),
}),
"b": cty.StringVal("b value"),
}),
cty.ObjectVal(map[string]cty.Value{
"a": cty.ListVal([]cty.Value{
cty.StringVal("new a0 value"),
cty.StringVal("new a1 value"),
}),
"b": cty.StringVal("new b value"),
}),
[]string{"a[1]"},
cty.ObjectVal(map[string]cty.Value{
"a": cty.ListVal([]cty.Value{
cty.StringVal("new a0 value"),
cty.StringVal("a1 value"),
}),
"b": cty.StringVal("new b value"),
}),
},
"map_index": {
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a0": cty.StringVal("a0 value"),
"a1": cty.StringVal("a1 value"),
}),
"b": cty.StringVal("b value"),
}),
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a0": cty.StringVal("new a0 value"),
"a1": cty.StringVal("new a1 value"),
}),
"b": cty.StringVal("b value"),
}),
[]string{`a["a1"]`},
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a0": cty.StringVal("new a0 value"),
"a1": cty.StringVal("a1 value"),
}),
"b": cty.StringVal("b value"),
}),
},
"map_index_no_config": {
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a0": cty.StringVal("a0 value"),
"a1": cty.StringVal("a1 value"),
}),
"b": cty.StringVal("b value"),
}),
cty.ObjectVal(map[string]cty.Value{
"a": cty.NullVal(cty.Map(cty.String)),
"b": cty.StringVal("b value"),
}),
[]string{`a["a1"]`},
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a1": cty.StringVal("a1 value"),
}),
"b": cty.StringVal("b value"),
}),
},
"missing_map_index": {
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a0": cty.StringVal("a0 value"),
"a1": cty.StringVal("a1 value"),
}),
"b": cty.StringVal("b value"),
}),
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapValEmpty(cty.String),
"b": cty.StringVal("b value"),
}),
[]string{`a["a1"]`},
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a1": cty.StringVal("a1 value"),
}),
"b": cty.StringVal("b value"),
}),
},
"missing_map_index_empty": {
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapValEmpty(cty.String),
}),
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a": cty.StringVal("a0 value"),
}),
}),
[]string{`a["a"]`},
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapValEmpty(cty.String),
}),
},
"missing_map_index_to_object": {
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a": cty.ObjectVal(map[string]cty.Value{
"a": cty.StringVal("aa0"),
"b": cty.StringVal("ab0"),
}),
"b": cty.ObjectVal(map[string]cty.Value{
"a": cty.StringVal("ba0"),
"b": cty.StringVal("bb0"),
}),
}),
}),
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapValEmpty(
cty.Object(map[string]cty.Type{
"a": cty.String,
"b": cty.String,
}),
),
}),
// we expect the config to be used here, as the ignore changes was
// `a["a"].b`, but the change was larger than that removing
// `a["a"]` entirely.
[]string{`a["a"].b`},
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapValEmpty(
cty.Object(map[string]cty.Type{
"a": cty.String,
"b": cty.String,
}),
),
}),
},
"missing_prior_map_index": {
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a0": cty.StringVal("a0 value"),
}),
"b": cty.StringVal("b value"),
}),
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a0": cty.StringVal("a0 value"),
"a1": cty.StringVal("new a1 value"),
}),
"b": cty.StringVal("b value"),
}),
[]string{`a["a1"]`},
cty.ObjectVal(map[string]cty.Value{
"a": cty.MapVal(map[string]cty.Value{
"a0": cty.StringVal("a0 value"),
}),
"b": cty.StringVal("b value"),
}),
},
"object attribute": {
cty.ObjectVal(map[string]cty.Value{
"a": cty.ObjectVal(map[string]cty.Value{
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