command/state-push: support pushing from stdin

command/state_push.go

@@ -2,6 +2,7 @@ package command
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"strings"
 
@@ -31,14 +32,28 @@ func (c *StatePushCommand) Run(args []string) int {
 		return 1
 	}
 
-	// Read the state
+	// Determine our reader for the input state. This is the filepath
+	// or stdin if "-" is given.
+	var r io.Reader = os.Stdin
+	if args[0] != "-" {
 		f, err := os.Open(args[0])
 		if err != nil {
 			c.Ui.Error(err.Error())
 			return 1
 		}
-	sourceState, err := terraform.ReadState(f)
-	f.Close()
+
+		// Note: we don't need to defer a Close here because we do a close
+		// automatically below directly after the read.
+
+		r = f
+	}
+
+	// Read the state
+	sourceState, err := terraform.ReadState(r)
+	if c, ok := r.(io.Closer); ok {
+		// Close the reader if possible right now since we're done with it.
+		c.Close()
+	}
 	if err != nil {
 		c.Ui.Error(fmt.Sprintf("Error reading source state %q: %s", args[0], err))
 		return 1
@@ -109,6 +124,10 @@ Usage: terraform state push [options] PATH
   This command works with local state (it will overwrite the local
   state), but is less useful for this use case.
 
+  If PATH is "-", then this command will read the state to push from stdin.
+  Data from stdin is not streamed to the backend: it is loaded completely
+  (until pipe close), verified, and then pushed.
+
 Options:
 
   -force              Write the state even if lineages don't match or the

command/state_push_test.go

@@ -1,10 +1,12 @@
 package command
 
 import (
+	"bytes"
 	"os"
 	"testing"
 
 	"github.com/hashicorp/terraform/helper/copy"
+	"github.com/hashicorp/terraform/terraform"
 	"github.com/mitchellh/cli"
 )
 
@@ -66,6 +68,42 @@ func TestStatePush_replaceMatch(t *testing.T) {
 	}
 }
 
+func TestStatePush_replaceMatchStdin(t *testing.T) {
+	// Create a temporary working directory that is empty
+	td := tempDir(t)
+	copy.CopyDir(testFixturePath("state-push-replace-match"), td)
+	defer os.RemoveAll(td)
+	defer testChdir(t, td)()
+
+	expected := testStateRead(t, "replace.tfstate")
+
+	// Setup the replacement to come from stdin
+	var buf bytes.Buffer
+	if err := terraform.WriteState(expected, &buf); err != nil {
+		t.Fatalf("err: %s")
+	}
+	defer testStdinPipe(t, &buf)()
+
+	p := testProvider()
+	ui := new(cli.MockUi)
+	c := &StatePushCommand{
+		Meta: Meta{
+			ContextOpts: testCtxConfig(p),
+			Ui:          ui,
+		},
+	}
+
+	args := []string{"-"}
+	if code := c.Run(args); code != 0 {
+		t.Fatalf("bad: %d\n\n%s", code, ui.ErrorWriter.String())
+	}
+
+	actual := testStateRead(t, "local-state.tfstate")
+	if !actual.Equal(expected) {
+		t.Fatalf("bad: %#v", actual)
+	}
+}
+
 func TestStatePush_lineageMismatch(t *testing.T) {
 	// Create a temporary working directory that is empty
 	td := tempDir(t)

website/source/docs/commands/state/push.html.md

@@ -22,6 +22,10 @@ Usage: `terraform state push [options] PATH`
 This command will push the state specified by PATH to the currently
 configured [backend](/docs/backends).
 
+If PATH is "-" then the state data to push is read from stdin. This data
+is loaded completely into memory and verified prior to being written to
+the destination state.
+
 Terraform will perform a number of safety checks to prevent you from
 making changes that appear to be unsafe: