Add metadata functions -json command

tfexec/metadata_functions.go

@@ -0,0 +1,39 @@
+package tfexec
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+
+	tfjson "github.com/hashicorp/terraform-json"
+)
+
+// MetadataFunctions represents the terraform metadata functions -json subcommand.
+func (tf *Terraform) MetadataFunctions(ctx context.Context) (*tfjson.MetadataFunctions, error) {
+	err := tf.compatible(ctx, tf1_4_0, nil)
+	if err != nil {
+		return nil, fmt.Errorf("terraform metadata functions was added in 1.4.0: %w", err)
+	}
+
+	functionsCmd := tf.metadataFunctionsCmd(ctx)
+
+	var ret tfjson.MetadataFunctions
+	err = tf.runTerraformCmdJSON(ctx, functionsCmd, &ret)
+	if err != nil {
+		return nil, err
+	}
+
+	err = ret.Validate()
+	if err != nil {
+		return nil, err
+	}
+
+	return &ret, nil
+}
+
+func (tf *Terraform) metadataFunctionsCmd(ctx context.Context, args ...string) *exec.Cmd {
+	allArgs := []string{"metadata", "functions", "-json"}
+	allArgs = append(allArgs, args...)
+
+	return tf.buildTerraformCmd(ctx, nil, allArgs...)
+}

tfexec/version.go

@@ -27,6 +27,7 @@ var (
 	tf0_15_2 = version.Must(version.NewVersion("0.15.2"))
 	tf0_15_3 = version.Must(version.NewVersion("0.15.3"))
 	tf1_1_0  = version.Must(version.NewVersion("1.1.0"))
+	tf1_4_0  = version.Must(version.NewVersion("1.4.0"))
 )
 
 // Version returns structured output from the terraform version command including both the Terraform CLI version