Implements the graph command (#257)

* Implements the graph command

* Adds version gating, additional tests

tfexec/graph.go

@@ -0,0 +1,85 @@
+package tfexec
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+type graphConfig struct {
+	plan       string
+	drawCycles bool
+	graphType  string
+}
+
+var defaultGraphOptions = graphConfig{}
+
+type GraphOption interface {
+	configureGraph(*graphConfig)
+}
+
+func (opt *GraphPlanOption) configureGraph(conf *graphConfig) {
+	conf.plan = opt.file
+}
+
+func (opt *DrawCyclesOption) configureGraph(conf *graphConfig) {
+	conf.drawCycles = opt.drawCycles
+}
+
+func (opt *GraphTypeOption) configureGraph(conf *graphConfig) {
+	conf.graphType = opt.graphType
+}
+
+func (tf *Terraform) Graph(ctx context.Context, opts ...GraphOption) (string, error) {
+	graphCmd, err := tf.graphCmd(ctx, opts...)
+	if err != nil {
+		return "", err
+	}
+	var outBuf strings.Builder
+	graphCmd.Stdout = &outBuf
+	err = tf.runTerraformCmd(ctx, graphCmd)
+	if err != nil {
+		return "", err
+	}
+
+	return outBuf.String(), nil
+
+}
+
+func (tf *Terraform) graphCmd(ctx context.Context, opts ...GraphOption) (*exec.Cmd, error) {
+	c := defaultGraphOptions
+
+	for _, o := range opts {
+		o.configureGraph(&c)
+	}
+
+	args := []string{"graph"}
+
+	if c.plan != "" {
+		// plan was a positional arguement prior to Terraform 0.15.0. Ensure proper use by checking version.
+		if err := tf.compatible(ctx, tf0_15_0, nil); err == nil {
+			args = append(args, "-plan="+c.plan)
+		} else {
+			args = append(args, c.plan)
+		}
+	}
+
+	if c.drawCycles {
+		err := tf.compatible(ctx, tf0_5_0, nil)
+		if err != nil {
+			return nil, fmt.Errorf("-draw-cycles was first introduced in Terraform 0.5.0: %w", err)
+		}
+		args = append(args, "-draw-cycles")
+	}
+
+	if c.graphType != "" {
+		err := tf.compatible(ctx, tf0_8_0, nil)
+		if err != nil {
+			return nil, fmt.Errorf("-graph-type was first introduced in Terraform 0.8.0: %w", err)
+		}
+		args = append(args, "-type="+c.graphType)
+	}
+
+	return tf.buildTerraformCmd(ctx, nil, args...), nil
+}

tfexec/graph_test.go

@@ -0,0 +1,76 @@
+package tfexec
+
+import (
+	"context"
+	"testing"
+
+	"github.com/hashicorp/terraform-exec/tfexec/internal/testutil"
+)
+
+func TestGraphCmd(t *testing.T) {
+	td := t.TempDir()
+
+	tf, err := NewTerraform(td, tfVersion(t, testutil.Latest013))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// empty env, to avoid environ mismatch in testing
+	tf.SetEnv(map[string]string{})
+
+	t.Run("defaults", func(t *testing.T) {
+		graphCmd, _ := tf.graphCmd(context.Background())
+
+		assertCmd(t, []string{
+			"graph",
+		}, nil, graphCmd)
+	})
+
+	t.Run("override all defaults", func(t *testing.T) {
+		graphCmd, _ := tf.graphCmd(context.Background(),
+			GraphPlan("teststate"),
+			DrawCycles(true),
+			GraphType("output"))
+
+		assertCmd(t, []string{
+			"graph",
+			"teststate",
+			"-draw-cycles",
+			"-type=output",
+		}, nil, graphCmd)
+	})
+}
+
+func TestGraphCmd15(t *testing.T) {
+	td := t.TempDir()
+
+	tf, err := NewTerraform(td, tfVersion(t, testutil.Latest015))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// empty env, to avoid environ mismatch in testing
+	tf.SetEnv(map[string]string{})
+
+	t.Run("defaults", func(t *testing.T) {
+		graphCmd, _ := tf.graphCmd(context.Background())
+
+		assertCmd(t, []string{
+			"graph",
+		}, nil, graphCmd)
+	})
+
+	t.Run("override all defaults", func(t *testing.T) {
+		graphCmd, _ := tf.graphCmd(context.Background(),
+			GraphPlan("teststate"),
+			DrawCycles(true),
+			GraphType("output"))
+
+		assertCmd(t, []string{
+			"graph",
+			"-plan=teststate",
+			"-draw-cycles",
+			"-type=output",
+		}, nil, graphCmd)
+	})
+}

tfexec/internal/e2etest/graph_test.go

@@ -0,0 +1,35 @@
+package e2etest
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"github.com/hashicorp/go-version"
+
+	"github.com/hashicorp/terraform-exec/tfexec"
+)
+
+func TestGraph(t *testing.T) {
+	runTest(t, "basic", func(t *testing.T, tfv *version.Version, tf *tfexec.Terraform) {
+		err := tf.Init(context.Background())
+		if err != nil {
+			t.Fatalf("error running Init in test directory: %s", err)
+		}
+
+		err = tf.Apply(context.Background())
+		if err != nil {
+			t.Fatalf("error running Apply: %s", err)
+		}
+
+		graphOutput, err := tf.Graph(context.Background())
+		if err != nil {
+			t.Fatalf("error running Graph: %s", err)
+		}
+
+		// Graph output differs slightly between versions, but resource subgraph remains consistent
+		if !strings.Contains(graphOutput, `"[root] null_resource.foo" [label = "null_resource.foo", shape = "box"]`) {
+			t.Fatalf("error running Graph. Graph output does not contain expected strings. Returned: %s", graphOutput)
+		}
+	})
+}

tfexec/options.go

@@ -118,6 +118,15 @@ func Destroy(destroy bool) *DestroyFlagOption {
 	return &DestroyFlagOption{destroy}
 }
 
+type DrawCyclesOption struct {
+	drawCycles bool
+}
+
+// DrawCycles represents the -draw-cycles flag.
+func DrawCycles(drawCycles bool) *DrawCyclesOption {
+	return &DrawCyclesOption{drawCycles}
+}
+
 type DryRunOption struct {
 	dryRun bool
 }
@@ -222,6 +231,15 @@ func Parallelism(n int) *ParallelismOption {
 	return &ParallelismOption{n}
 }
 
+type GraphPlanOption struct {
+	file string
+}
+
+// GraphPlan represents the -plan flag which is a specified plan file string
+func GraphPlan(file string) *GraphPlanOption {
+	return &GraphPlanOption{file}
+}
+
 type PlatformOption struct {
 	platform string
 }
@@ -344,6 +362,14 @@ func Target(resource string) *TargetOption {
 	return &TargetOption{resource}
 }
 
+type GraphTypeOption struct {
+	graphType string
+}
+
+func GraphType(graphType string) *GraphTypeOption {
+	return &GraphTypeOption{graphType}
+}
+
 type UpdateOption struct {
 	update bool
 }

tfexec/version.go

@@ -15,8 +15,10 @@ import (
 
 var (
 	tf0_4_1  = version.Must(version.NewVersion("0.4.1"))
+	tf0_5_0  = version.Must(version.NewVersion("0.5.0"))
 	tf0_6_13 = version.Must(version.NewVersion("0.6.13"))
 	tf0_7_7  = version.Must(version.NewVersion("0.7.7"))
+	tf0_8_0  = version.Must(version.NewVersion("0.8.0"))
 	tf0_10_0 = version.Must(version.NewVersion("0.10.0"))
 	tf0_12_0 = version.Must(version.NewVersion("0.12.0"))
 	tf0_13_0 = version.Must(version.NewVersion("0.13.0"))