From 45c168bb5bfc273cf496ab43cb5d70a2990f8dd6 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 3 Jun 2014 16:11:02 -0700
Subject: [PATCH] terraform: multierrors

---
 terraform/multi_error.go      | 50 +++++++++++++++++++++++++++++++
 terraform/multi_error_test.go | 56 +++++++++++++++++++++++++++++++++++
 terraform/terraform.go        | 15 ++++++----
 3 files changed, 115 insertions(+), 6 deletions(-)
 create mode 100644 terraform/multi_error.go
 create mode 100644 terraform/multi_error_test.go

diff --git a/terraform/multi_error.go b/terraform/multi_error.go
new file mode 100644
index 000000000..9f11b95d8
--- /dev/null
+++ b/terraform/multi_error.go
@@ -0,0 +1,50 @@
+package terraform
+
+import (
+	"fmt"
+	"strings"
+)
+
+// MultiError is an error type to track multiple errors. This is used to
+// accumulate errors in cases such as configuration parsing, and returning
+// them as a single error.
+type MultiError struct {
+	Errors []error
+}
+
+func (e *MultiError) Error() string {
+	points := make([]string, len(e.Errors))
+	for i, err := range e.Errors {
+		points[i] = fmt.Sprintf("* %s", err)
+	}
+
+	return fmt.Sprintf(
+		"%d error(s) occurred:\n\n%s",
+		len(e.Errors), strings.Join(points, "\n"))
+}
+
+// MultiErrorAppend is a helper function that will append more errors
+// onto a MultiError in order to create a larger multi-error. If the
+// original error is not a MultiError, it will be turned into one.
+func MultiErrorAppend(err error, errs ...error) *MultiError {
+	if err == nil {
+		err = new(MultiError)
+	}
+
+	switch err := err.(type) {
+	case *MultiError:
+		if err == nil {
+			err = new(MultiError)
+		}
+
+		err.Errors = append(err.Errors, errs...)
+		return err
+	default:
+		newErrs := make([]error, len(errs)+1)
+		newErrs[0] = err
+		copy(newErrs[1:], errs)
+		return &MultiError{
+			Errors: newErrs,
+		}
+	}
+}
diff --git a/terraform/multi_error_test.go b/terraform/multi_error_test.go
new file mode 100644
index 000000000..44e07babf
--- /dev/null
+++ b/terraform/multi_error_test.go
@@ -0,0 +1,56 @@
+package terraform
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestMultiError_Impl(t *testing.T) {
+	var raw interface{}
+	raw = &MultiError{}
+	if _, ok := raw.(error); !ok {
+		t.Fatal("MultiError must implement error")
+	}
+}
+
+func TestMultiErrorError(t *testing.T) {
+	expected := `2 error(s) occurred:
+
+* foo
+* bar`
+
+	errors := []error{
+		errors.New("foo"),
+		errors.New("bar"),
+	}
+
+	multi := &MultiError{errors}
+	if multi.Error() != expected {
+		t.Fatalf("bad: %s", multi.Error())
+	}
+}
+
+func TestMultiErrorAppend_MultiError(t *testing.T) {
+	original := &MultiError{
+		Errors: []error{errors.New("foo")},
+	}
+
+	result := MultiErrorAppend(original, errors.New("bar"))
+	if len(result.Errors) != 2 {
+		t.Fatalf("wrong len: %d", len(result.Errors))
+	}
+
+	original = &MultiError{}
+	result = MultiErrorAppend(original, errors.New("bar"))
+	if len(result.Errors) != 1 {
+		t.Fatalf("wrong len: %d", len(result.Errors))
+	}
+}
+
+func TestMultiErrorAppend_NonMultiError(t *testing.T) {
+	original := errors.New("foo")
+	result := MultiErrorAppend(original, errors.New("bar"))
+	if len(result.Errors) != 2 {
+		t.Fatalf("wrong len: %d", len(result.Errors))
+	}
+}
diff --git a/terraform/terraform.go b/terraform/terraform.go
index 837e2be01..7290996fb 100644
--- a/terraform/terraform.go
+++ b/terraform/terraform.go
@@ -31,6 +31,8 @@ type Config struct {
 // time, as well as richer checks such as verifying that the resource providers
 // can be properly initialized, can be configured, etc.
 func New(c *Config) (*Terraform, error) {
+	var errs []error
+
 	// Validate that all required variables have values
 	required := make(map[string]struct{})
 	for k, v := range c.Config.Variables {
@@ -42,14 +44,10 @@ func New(c *Config) (*Terraform, error) {
 		delete(required, k)
 	}
 	if len(required) > 0 {
-		errs := make([]error, 0, len(required))
 		for k, _ := range required {
 			errs = append(errs, fmt.Errorf(
 				"Required variable not set: %s", k))
 		}
-
-		// TODO(mitchellh): Return multi-error
-		return nil, errs[0]
 	}
 
 	// Go through each resource and match it up to a provider
@@ -90,14 +88,19 @@ func New(c *Config) (*Terraform, error) {
 
 		if provider == nil {
 			// We never found a matching provider.
-			return nil, fmt.Errorf(
+			errs = append(errs, fmt.Errorf(
 				"Provider for resource %s not found.",
-				r.Id())
+				r.Id()))
 		}
 
 		mapping[r] = provider
 	}
 
+	// If we accumulated any errors, then return them all
+	if len(errs) > 0 {
+		return nil, &MultiError{Errors: errs}
+	}
+
 	return &Terraform{
 		config:    c.Config,
 		mapping:   mapping,