config: make Merge an exported func

config/config_tree.go

@@ -1,9 +1,5 @@
 package config
 
-import (
-	"fmt"
-)
-
 // configTree represents a tree of configurations where the root is the
 // first file and its children are the configurations it has imported.
 type configTree struct {
@@ -36,72 +32,12 @@ func (t *configTree) Flatten() (*Config, error) {
 	childConfigs = childConfigs[1:]
 	for _, config2 := range childConfigs {
 		var err error
-		config, err = mergeConfig(config, config2)
+		config, err = Merge(config, config2)
 		if err != nil {
 			return nil, err
 		}
 	}
 
 	// Merge the final merged child config with our own
-	return mergeConfig(config, t.Config)
-}
-
-func mergeConfig(c1, c2 *Config) (*Config, error) {
-	c := new(Config)
-
-	// Merge variables: Variable merging is quite simple. Set fields in
-	// later set variables override those earlier.
-	c.Variables = c1.Variables
-	for k, v2 := range c2.Variables {
-		v1, ok := c.Variables[k]
-		if ok {
-			if v2.Default == "" {
-				v2.Default = v1.Default
-			}
-			if v2.Description == "" {
-				v2.Description = v1.Description
-			}
-		}
-
-		c.Variables[k] = v2
-	}
-
-	// Merge outputs: If they collide, just take the latest one for now. In
-	// the future, we might provide smarter merge functionality.
-	c.Outputs = make(map[string]*Output)
-	for k, v := range c1.Outputs {
-		c.Outputs[k] = v
-	}
-	for k, v := range c2.Outputs {
-		c.Outputs[k] = v
-	}
-
-	// Merge provider configs: If they collide, we just take the latest one
-	// for now. In the future, we might provide smarter merge functionality.
-	c.ProviderConfigs = make(map[string]*ProviderConfig)
-	for k, v := range c1.ProviderConfigs {
-		c.ProviderConfigs[k] = v
-	}
-	for k, v := range c2.ProviderConfigs {
-		c.ProviderConfigs[k] = v
-	}
-
-	// Merge resources: If they collide, we just take the latest one
-	// for now. In the future, we might provide smarter merge functionality.
-	resources := make(map[string]*Resource)
-	for _, r := range c1.Resources {
-		id := fmt.Sprintf("%s[%s]", r.Type, r.Name)
-		resources[id] = r
-	}
-	for _, r := range c2.Resources {
-		id := fmt.Sprintf("%s[%s]", r.Type, r.Name)
-		resources[id] = r
-	}
-
-	c.Resources = make([]*Resource, 0, len(resources))
-	for _, r := range resources {
-		c.Resources = append(c.Resources, r)
-	}
-
-	return c, nil
+	return Merge(config, t.Config)
 }

config/loader.go

@@ -50,7 +50,7 @@ func LoadDir(path string) (*Config, error) {
 		}
 
 		if result != nil {
-			result, err = mergeConfig(result, c)
+			result, err = Merge(result, c)
 			if err != nil {
 				return nil, err
 			}

config/merge.go

@@ -0,0 +1,65 @@
+package config
+
+import (
+	"fmt"
+)
+
+func Merge(c1, c2 *Config) (*Config, error) {
+	c := new(Config)
+
+	// Merge variables: Variable merging is quite simple. Set fields in
+	// later set variables override those earlier.
+	c.Variables = c1.Variables
+	for k, v2 := range c2.Variables {
+		v1, ok := c.Variables[k]
+		if ok {
+			if v2.Default == "" {
+				v2.Default = v1.Default
+			}
+			if v2.Description == "" {
+				v2.Description = v1.Description
+			}
+		}
+
+		c.Variables[k] = v2
+	}
+
+	// Merge outputs: If they collide, just take the latest one for now. In
+	// the future, we might provide smarter merge functionality.
+	c.Outputs = make(map[string]*Output)
+	for k, v := range c1.Outputs {
+		c.Outputs[k] = v
+	}
+	for k, v := range c2.Outputs {
+		c.Outputs[k] = v
+	}
+
+	// Merge provider configs: If they collide, we just take the latest one
+	// for now. In the future, we might provide smarter merge functionality.
+	c.ProviderConfigs = make(map[string]*ProviderConfig)
+	for k, v := range c1.ProviderConfigs {
+		c.ProviderConfigs[k] = v
+	}
+	for k, v := range c2.ProviderConfigs {
+		c.ProviderConfigs[k] = v
+	}
+
+	// Merge resources: If they collide, we just take the latest one
+	// for now. In the future, we might provide smarter merge functionality.
+	resources := make(map[string]*Resource)
+	for _, r := range c1.Resources {
+		id := fmt.Sprintf("%s[%s]", r.Type, r.Name)
+		resources[id] = r
+	}
+	for _, r := range c2.Resources {
+		id := fmt.Sprintf("%s[%s]", r.Type, r.Name)
+		resources[id] = r
+	}
+
+	c.Resources = make([]*Resource, 0, len(resources))
+	for _, r := range resources {
+		c.Resources = append(c.Resources, r)
+	}
+
+	return c, nil
+}