Add support for Vault agent environment variables | VAULT-16059

config/template.go

@@ -118,6 +118,11 @@ type TemplateConfig struct {
 	// and causes an error if a relative path tries to traverse outside that
 	// prefix.
 	SandboxPath *string `mapstructure:"sandbox_path"`
+
+	// MapToEnvironmentVariable is the name of the environment variable this
+	// template should map to. This field is only applicable used when
+	// consul-template is used as a library.
+	MapToEnvironmentVariable *string `mapstructure:"-"`
 }
 
 // DefaultTemplateConfig returns a configuration that is populated with the
@@ -184,6 +189,8 @@ func (c *TemplateConfig) Copy() *TemplateConfig {
 
 	o.SandboxPath = c.SandboxPath
 
+	o.MapToEnvironmentVariable = c.MapToEnvironmentVariable
+
 	return &o
 }
 
@@ -288,6 +295,10 @@ func (c *TemplateConfig) Merge(o *TemplateConfig) *TemplateConfig {
 		r.SandboxPath = o.SandboxPath
 	}
 
+	if o.MapToEnvironmentVariable != nil {
+		r.MapToEnvironmentVariable = o.MapToEnvironmentVariable
+	}
+
 	return r
 }
 
@@ -410,7 +421,8 @@ func (c *TemplateConfig) GoString() string {
 		"LeftDelim:%s, "+
 		"RightDelim:%s, "+
 		"FunctionDenylist:%s, "+
-		"SandboxPath:%s"+
+		"SandboxPath:%s "+
+		"MapToEnvironmentVariable:%s"+
 		"}",
 		BoolGoString(c.Backup),
 		c.Command,
@@ -428,6 +440,7 @@ func (c *TemplateConfig) GoString() string {
 		StringGoString(c.RightDelim),
 		combineLists(c.FunctionDenylist, c.FunctionDenylistDeprecated),
 		StringGoString(c.SandboxPath),
+		StringGoString(c.MapToEnvironmentVariable),
 	)
 }
 
@@ -444,9 +457,14 @@ func (c *TemplateConfig) Display() string {
 		source = String("(dynamic)")
 	}
 
+	destination := c.Destination
+	if StringPresent(c.MapToEnvironmentVariable) {
+		destination = c.MapToEnvironmentVariable
+	}
+
 	return fmt.Sprintf("%q => %q",
 		StringVal(source),
-		StringVal(c.Destination),
+		StringVal(destination),
 	)
 }