terraform: simplify semantic checks out into sep functions

terraform/semantics.go

@@ -0,0 +1,134 @@
+package terraform
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/hashicorp/terraform/config"
+)
+
+// smcProviders matches up the resources with a provider
+// those providers and does the initial `Configure` on the provider.
+func smcProviders(c *Config) (map[*config.Resource]ResourceProvider, []error) {
+	var errs []error
+
+	// Keep track of providers we know we couldn't instantiate so
+	// that we don't get a ton of errors about the same provider.
+	failures := make(map[string]struct{})
+
+	// Go through each resource and match it up to a provider
+	mapping := make(map[*config.Resource]ResourceProvider)
+	providers := make(map[string]ResourceProvider)
+
+ResourceLoop:
+	for _, r := range c.Config.Resources {
+		// Find the prefixes that match this in the order of
+		// longest matching first (most specific)
+		prefixes := matchingPrefixes(r.Type, c.Providers)
+
+		if len(prefixes) > 0 {
+			if _, ok := failures[prefixes[0]]; ok {
+				// We already failed this provider, meaning this
+				// resource will never succeed, so just continue.
+				continue
+			}
+		}
+
+		// Go through each prefix and instantiate if necessary, then
+		// verify if this provider is of use to us or not.
+		var provider ResourceProvider = nil
+		for _, prefix := range prefixes {
+			// Initialize the provider
+			p, ok := providers[prefix]
+			if !ok {
+				var err error
+				p, err = c.Providers[prefix]()
+				if err != nil {
+					errs = append(errs, fmt.Errorf(
+						"Error instantiating resource provider for "+
+							"prefix %s: %s", prefix, err))
+
+					// Record the error so that we don't check it again
+					failures[prefix] = struct{}{}
+
+					// Jump to the next resource
+					continue ResourceLoop
+				}
+
+				providers[prefix] = p
+			}
+
+			// Test if this provider matches what we need
+			if !ProviderSatisfies(p, r.Type) {
+				continue
+			}
+
+			// A match! Set it and break
+			provider = p
+			break
+		}
+
+		if provider == nil {
+			// We never found a matching provider.
+			errs = append(errs, fmt.Errorf(
+				"Provider for resource %s not found.",
+				r.Id()))
+		}
+
+		mapping[r] = provider
+	}
+
+	if len(errs) > 0 {
+		return nil, errs
+	}
+
+	return mapping, nil
+}
+
+// smcVariables does all the semantic checks to verify that the
+// variables given in the configuration to instantiate a Terraform
+// struct are valid.
+func smcVariables(c *Config) []error {
+	var errs []error
+
+	// Check that all required variables are present
+	required := make(map[string]struct{})
+	for k, v := range c.Config.Variables {
+		if v.Required() {
+			required[k] = struct{}{}
+		}
+	}
+	for k, _ := range c.Variables {
+		delete(required, k)
+	}
+	if len(required) > 0 {
+		for k, _ := range required {
+			errs = append(errs, fmt.Errorf(
+				"Required variable not set: %s", k))
+		}
+	}
+
+	// TODO(mitchellh): variables that are unknown
+
+	return errs
+}
+
+// matchingPrefixes takes a resource type and a set of resource
+// providers we know about by prefix and returns a list of prefixes
+// that might be valid for that resource.
+//
+// The list returned is in the order that they should be attempted.
+func matchingPrefixes(
+	t string,
+	ps map[string]ResourceProviderFactory) []string {
+	result := make([]string, 0, 1)
+	for prefix, _ := range ps {
+		if strings.HasPrefix(t, prefix) {
+			result = append(result, prefix)
+		}
+	}
+
+	// TODO(mitchellh): Order by longest prefix first
+
+	return result
+}

terraform/terraform.go

@@ -2,7 +2,6 @@ package terraform
 
 import (
 	"fmt"
-	"strings"
 	"sync"
 
 	"github.com/hashicorp/terraform/config"
@@ -37,68 +36,14 @@ func New(c *Config) (*Terraform, error) {
 	var errs []error
 
 	// Validate that all required variables have values
-	required := make(map[string]struct{})
+	if err := smcVariables(c); err != nil {
-	for k, v := range c.Config.Variables {
+		errs = append(errs, err...)
-		if v.Required() {
-			required[k] = struct{}{}
-		}
-	}
-	for k, _ := range c.Variables {
-		delete(required, k)
-	}
-	if len(required) > 0 {
-		for k, _ := range required {
-			errs = append(errs, fmt.Errorf(
-				"Required variable not set: %s", k))
-		}
 	}
 
-	// TODO(mitchellh): variables that are unknown
+	// Match all the resources with a provider and initialize the providers
-
+	mapping, err := smcProviders(c)
-	// Go through each resource and match it up to a provider
+	if err != nil {
-	mapping := make(map[*config.Resource]ResourceProvider)
+		errs = append(errs, err...)
-	providers := make(map[string]ResourceProvider)
-	for _, r := range c.Config.Resources {
-		// Find the prefixes that match this in the order of
-		// longest matching first (most specific)
-		prefixes := matchingPrefixes(r.Type, c.Providers)
-
-		// Go through each prefix and instantiate if necessary, then
-		// verify if this provider is of use to us or not.
-		var provider ResourceProvider = nil
-		for _, prefix := range prefixes {
-			p, ok := providers[prefix]
-			if !ok {
-				var err error
-				p, err = c.Providers[prefix]()
-				if err != nil {
-					err = fmt.Errorf(
-						"Error instantiating resource provider for "+
-							"prefix %s: %s", prefix, err)
-					return nil, err
-				}
-
-				providers[prefix] = p
-			}
-
-			// Test if this provider matches what we need
-			if !ProviderSatisfies(p, r.Type) {
-				continue
-			}
-
-			// A match! Set it and break
-			provider = p
-			break
-		}
-
-		if provider == nil {
-			// We never found a matching provider.
-			errs = append(errs, fmt.Errorf(
-				"Provider for resource %s not found.",
-				r.Id()))
-		}
-
-		mapping[r] = provider
 	}
 
 	// Build the resource graph
@@ -203,23 +148,3 @@ func (t *Terraform) diffWalkFn(
 		return nil
 	}
 }
-
-// matchingPrefixes takes a resource type and a set of resource
-// providers we know about by prefix and returns a list of prefixes
-// that might be valid for that resource.
-//
-// The list returned is in the order that they should be attempted.
-func matchingPrefixes(
-	t string,
-	ps map[string]ResourceProviderFactory) []string {
-	result := make([]string, 0, 1)
-	for prefix, _ := range ps {
-		if strings.HasPrefix(t, prefix) {
-			result = append(result, prefix)
-		}
-	}
-
-	// TODO(mitchellh): Order by longest prefix first
-
-	return result
-}

terraform/terraform_test.go

@@ -41,17 +41,17 @@ func TestNew(t *testing.T) {
 	}
 
 	/*
-	val := testProviderMock(mapping["aws_instance.foo"]).
+		val := testProviderMock(mapping["aws_instance.foo"]).
-		ConfigureCommonConfig.TFComputedPlaceholder
+			ConfigureCommonConfig.TFComputedPlaceholder
-	if val == "" {
+		if val == "" {
-		t.Fatal("should have computed placeholder")
+			t.Fatal("should have computed placeholder")
-	}
+		}
 
-	val = testProviderMock(mapping["aws_instance.bar"]).
+		val = testProviderMock(mapping["aws_instance.bar"]).
-		ConfigureCommonConfig.TFComputedPlaceholder
+			ConfigureCommonConfig.TFComputedPlaceholder
-	if val == "" {
+		if val == "" {
-		t.Fatal("should have computed placeholder")
+			t.Fatal("should have computed placeholder")
-	}
+		}
 	*/
 }