correcly parse env variables during apply

Input variables taken from the environment have no type information, so
are initially stored as strings. When we compare those for validation
during apply, we have to make sure to use the same parsing logic used in
the plan in order to compare them with the stored variables.

internal/backend/local/backend_apply.go

@@ -259,33 +259,26 @@ func (b *Local) opApply(
 		// same parsing logic from the plan to generate the diagnostics.
 		undeclaredVariables := map[string]backendrun.UnparsedVariableValue{}
 
-		for varName, rawV := range op.Variables {
+		parsedVars, _ := backendrun.ParseVariableValues(op.Variables, lr.Config.Module.Variables)
+
+		for varName := range op.Variables {
+			parsedVar, parsed := parsedVars[varName]
+
 			decl, ok := lr.Config.Module.Variables[varName]
-			if !ok {
+			if !ok || !parsed {
 				// We'll try to parse this and handle diagnostics for missing
 				// variables with ParseUndeclaredVariableValues after.
-				undeclaredVariables[varName] = rawV
-				continue
-			}
-
-			// We're "parsing" only to get the resulting value's SourceType,
-			// so we'll use configs.VariableParseLiteral just because it's
-			// the most liberal interpretation and so least likely to
-			// fail with an unrelated error.
-			v, _ := rawV.ParseVariableValue(configs.VariableParseLiteral)
-			if v == nil {
-				// We'll ignore any that don't parse at all, because
-				// they'll fail elsewhere in this process anyway.
+				undeclaredVariables[varName] = op.Variables[varName]
 				continue
 			}
 
 			var rng *hcl.Range
-			if v.HasSourceRange() {
-				rng = v.SourceRange.ToHCL().Ptr()
+			if parsedVar.HasSourceRange() {
+				rng = parsedVar.SourceRange.ToHCL().Ptr()
 			}
 
 			// If the var is declared as ephemeral in config, go ahead and handle it
-			if ok && decl.Ephemeral {
+			if decl.Ephemeral {
 				// Determine whether this is an apply-time variable, i.e. an
 				// ephemeral variable that was set (non-null) during the
 				// planning phase.
@@ -311,17 +304,9 @@ func (b *Local) opApply(
 					continue
 				}
 
-				// Get the value of the variable, because we'll need it for
-				// the next two steps.
-				val, valDiags := rawV.ParseVariableValue(decl.ParsingMode)
-				diags = diags.Append(valDiags)
-				if valDiags.HasErrors() {
-					continue
-				}
-
 				// If this is an apply-time variable, the user must supply a
 				// value during apply: it can't be null.
-				if applyTimeVar && val.Value.IsNull() {
+				if applyTimeVar && parsedVar.Value.IsNull() {
 					diags = diags.Append(&hcl.Diagnostic{
 						Severity: hcl.DiagError,
 						Summary:  "Ephemeral variable must be set for apply",
@@ -336,17 +321,17 @@ func (b *Local) opApply(
 				// If we get here, we are in possession of a non-null
 				// ephemeral apply-time input variable, and need only pass
 				// its value on to the ApplyOpts.
-				applyTimeValues[varName] = val
+				applyTimeValues[varName] = parsedVar
 			} else {
 				// If a non-ephemeral variable is set differently between plan and apply, we should emit a diagnostic.
 				plannedVariableValue, ok := plan.VariableValues[varName]
 				if !ok {
 					// We'll catch this with ParseUndeclaredVariableValues after
-					undeclaredVariables[varName] = rawV
+					undeclaredVariables[varName] = op.Variables[varName]
 					continue
 				}
 
-				val, err := plannedVariableValue.Decode(cty.DynamicPseudoType)
+				plannedVar, err := plannedVariableValue.Decode(cty.DynamicPseudoType)
 				if err != nil {
 					diags = diags.Append(&hcl.Diagnostic{
 						Severity: hcl.DiagError,
@@ -355,11 +340,11 @@ func (b *Local) opApply(
 						Subject:  rng,
 					})
 				} else {
-					if v.Value.Equals(val).False() {
+					if parsedVar.Value.Equals(plannedVar).False() {
 						diags = diags.Append(&hcl.Diagnostic{
 							Severity: hcl.DiagError,
 							Summary:  "Can't change variable when applying a saved plan",
-							Detail:   fmt.Sprintf("The variable %s cannot be set using the -var and -var-file options when applying a saved plan file, because a saved plan includes the variable values that were set when it was created. The saved plan specifies %s as the value whereas during apply the value %s was %s. To declare an ephemeral variable which is not saved in the plan file, use ephemeral = true.", varName, viewsjson.CompactValueStr(v.Value), viewsjson.CompactValueStr(val), v.SourceType.DiagnosticLabel()),
+							Detail:   fmt.Sprintf("The variable %s cannot be set using the -var and -var-file options when applying a saved plan file, because a saved plan includes the variable values that were set when it was created. The saved plan specifies %s as the value whereas during apply the value %s was %s. To declare an ephemeral variable which is not saved in the plan file, use ephemeral = true.", varName, viewsjson.CompactValueStr(parsedVar.Value), viewsjson.CompactValueStr(plannedVar), parsedVar.SourceType.DiagnosticLabel()),
 							Subject:  rng,
 						})
 					}