terraform: lang.Data fake for use in unit tests

Our real implementation of the lang.Data interface depends on just about
everything else in the modules runtime to implement its behavior, and so
it's not really appropriate to use in unit tests.

This new implementation is considerably simpler, just returning values
predefined in a set of fixed tables. This is appropriate for unit tests of
features that perform expression evaluation as a side-effect of their work
but that don't contribute their own values to the real evaluation data
implementation.

Author: apparentlymart

internal/terraform/evaluate_test.go

@@ -4,6 +4,7 @@
 package terraform
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/davecgh/go-spew/spew"
@@ -617,3 +618,102 @@ func evaluatorForModule(stateSync *states.SyncState, changesSync *plans.ChangesS
 		NamedValues: namedvals.NewState(),
 	}
 }
+
+// fakeEvaluationData is an implementation of [lang.Data] that answers most
+// questions just by returning data directly from the maps stored inside it.
+type fakeEvaluationData struct {
+	checkBlocks    map[addrs.Check]cty.Value
+	countAttrs     map[addrs.CountAttr]cty.Value
+	forEachAttrs   map[addrs.ForEachAttr]cty.Value
+	inputVariables map[addrs.InputVariable]cty.Value
+	localValues    map[addrs.LocalValue]cty.Value
+	modules        map[addrs.ModuleCall]cty.Value
+	outputValues   map[addrs.OutputValue]cty.Value
+	pathAttrs      map[addrs.PathAttr]cty.Value
+	resources      map[addrs.Resource]cty.Value
+	runBlocks      map[addrs.Run]cty.Value
+	terraformAttrs map[addrs.TerraformAttr]cty.Value
+
+	// staticValidateRefs optionally implements [lang.Data.StaticValidateReferences],
+	// but can be left as nil to just skip static validation altogether.
+	staticValidateRefs func(refs []*addrs.Reference, self addrs.Referenceable, source addrs.Referenceable) tfdiags.Diagnostics
+}
+
+var _ lang.Data = (*fakeEvaluationData)(nil)
+
+func fakeEvaluationDataLookup[Addr interface {
+	comparable
+	addrs.Referenceable
+}](addr Addr, _ tfdiags.SourceRange, table map[Addr]cty.Value) (cty.Value, tfdiags.Diagnostics) {
+	ret, ok := table[addr]
+	if !ok {
+		var diags tfdiags.Diagnostics
+		diags = diags.Append(fmt.Errorf("fakeEvaluationData does not know about %s", addr))
+		return cty.DynamicVal, diags
+	}
+	return ret, nil
+}
+
+// GetCheckBlock implements lang.Data.
+func (d *fakeEvaluationData) GetCheckBlock(addr addrs.Check, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.checkBlocks)
+}
+
+// GetCountAttr implements lang.Data.
+func (d *fakeEvaluationData) GetCountAttr(addr addrs.CountAttr, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.countAttrs)
+}
+
+// GetForEachAttr implements lang.Data.
+func (d *fakeEvaluationData) GetForEachAttr(addr addrs.ForEachAttr, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.forEachAttrs)
+}
+
+// GetInputVariable implements lang.Data.
+func (d *fakeEvaluationData) GetInputVariable(addr addrs.InputVariable, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.inputVariables)
+}
+
+// GetLocalValue implements lang.Data.
+func (d *fakeEvaluationData) GetLocalValue(addr addrs.LocalValue, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.localValues)
+}
+
+// GetModule implements lang.Data.
+func (d *fakeEvaluationData) GetModule(addr addrs.ModuleCall, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.modules)
+}
+
+// GetOutput implements lang.Data.
+func (d *fakeEvaluationData) GetOutput(addr addrs.OutputValue, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.outputValues)
+}
+
+// GetPathAttr implements lang.Data.
+func (d *fakeEvaluationData) GetPathAttr(addr addrs.PathAttr, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.pathAttrs)
+}
+
+// GetResource implements lang.Data.
+func (d *fakeEvaluationData) GetResource(addr addrs.Resource, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.resources)
+}
+
+// GetRunBlock implements lang.Data.
+func (d *fakeEvaluationData) GetRunBlock(addr addrs.Run, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.runBlocks)
+}
+
+// GetTerraformAttr implements lang.Data.
+func (d *fakeEvaluationData) GetTerraformAttr(addr addrs.TerraformAttr, rng tfdiags.SourceRange) (cty.Value, tfdiags.Diagnostics) {
+	return fakeEvaluationDataLookup(addr, rng, d.terraformAttrs)
+}
+
+// StaticValidateReferences implements lang.Data.
+func (d *fakeEvaluationData) StaticValidateReferences(refs []*addrs.Reference, self addrs.Referenceable, source addrs.Referenceable) tfdiags.Diagnostics {
+	if d.staticValidateRefs == nil {
+		// By default we just skip static validation
+		return nil
+	}
+	return d.staticValidateRefs(refs, self, source)
+}