From 290579ac7fc21b9770dd35aa4634b23aa69aa183 Mon Sep 17 00:00:00 2001
From: Mike Farah <mikefarah@gmail.com>
Date: Mon, 16 Dec 2019 20:38:55 +1100
Subject: [PATCH] Handle simple aliases

---
 commands_test.go            |  9 +++++++++
 examples/simple-anchor.yaml |  4 ++++
 pkg/yqlib/data_navigator.go | 22 ++++++++++++++++++----
 pkg/yqlib/lib.go            | 20 +++++++++++---------
 4 files changed, 42 insertions(+), 13 deletions(-)
 create mode 100644 examples/simple-anchor.yaml

diff --git a/commands_test.go b/commands_test.go
index 58d58e14..fa497bfd 100644
--- a/commands_test.go
+++ b/commands_test.go
@@ -112,6 +112,15 @@ func TestReadCmd(t *testing.T) {
 // 	test.AssertResult(t, "21\n", result.Output)
 // }
 
+func TestReadAnchorsCmd(t *testing.T) {
+	cmd := getRootCommand()
+	result := test.RunCmd(cmd, "read examples/simple-anchor.yaml foobar.a")
+	if result.Error != nil {
+		t.Error(result.Error)
+	}
+	test.AssertResult(t, "1\n", result.Output)
+}
+
 func TestReadInvalidDocumentIndexCmd(t *testing.T) {
 	cmd := getRootCommand()
 	result := test.RunCmd(cmd, "read -df examples/sample.yaml b.c")
diff --git a/examples/simple-anchor.yaml b/examples/simple-anchor.yaml
new file mode 100644
index 00000000..c83b2dcf
--- /dev/null
+++ b/examples/simple-anchor.yaml
@@ -0,0 +1,4 @@
+foo: &foo
+  a: 1
+
+foobar: *foo
\ No newline at end of file
diff --git a/pkg/yqlib/data_navigator.go b/pkg/yqlib/data_navigator.go
index 1e2d03e0..e1493eb3 100644
--- a/pkg/yqlib/data_navigator.go
+++ b/pkg/yqlib/data_navigator.go
@@ -18,14 +18,16 @@ type DataNavigator interface {
 }
 
 type navigator struct {
-	log *logging.Logger
+	log           *logging.Logger
+	followAliases bool
 }
 
 type VisitorFn func(*yaml.Node) error
 
-func NewDataNavigator(l *logging.Logger) DataNavigator {
+func NewDataNavigator(l *logging.Logger, followAliases bool) DataNavigator {
 	return &navigator{
-		log: l,
+		log:           l,
+		followAliases: followAliases,
 	}
 }
 
@@ -147,6 +149,10 @@ func (n *navigator) GuessKind(tail []string, guess yaml.Kind) yaml.Kind {
 	if tail[0] == "*" && (guess == yaml.SequenceNode || guess == yaml.MappingNode) {
 		return guess
 	}
+	if guess == yaml.AliasNode {
+		n.log.Debug("guess was an alias, okey doke.")
+		return guess
+	}
 	return yaml.MappingNode
 }
 
@@ -172,6 +178,7 @@ func (n *navigator) DebugNode(value *yaml.Node) {
 }
 
 func (n *navigator) recurse(value *yaml.Node, head string, tail []string, visitor VisitorFn) error {
+	n.log.Debug("recursing, processing %v", head)
 	switch value.Kind {
 	case yaml.MappingNode:
 		n.log.Debug("its a map with %v entries", len(value.Content)/2)
@@ -187,6 +194,13 @@ func (n *navigator) recurse(value *yaml.Node, head string, tail []string, visito
 			return n.appendArray(value, tail, visitor)
 		}
 		return n.recurseArray(value, head, tail, visitor)
+	case yaml.AliasNode:
+		n.log.Debug("its an alias, followAliases: %v", n.followAliases)
+		n.DebugNode(value.Alias)
+		if n.followAliases == true {
+			return n.recurse(value.Alias, head, tail, visitor)
+		}
+		return nil
 	default:
 		return nil
 	}
@@ -237,7 +251,7 @@ func (n *navigator) visitMatchingEntries(contents []*yaml.Node, key string, visi
 	// so keys are in the even indexes, values in odd.
 	for index := 0; index < len(contents); index = index + 2 {
 		content := contents[index]
-		n.log.Debug("index %v, checking %v", index, content.Value)
+		n.log.Debug("index %v, checking %v", index, content.Value))
 		if n.matchesKey(key, content.Value) {
 			errorVisiting := visit(index)
 			if errorVisiting != nil {
diff --git a/pkg/yqlib/lib.go b/pkg/yqlib/lib.go
index 2415daea..eb3dc6db 100644
--- a/pkg/yqlib/lib.go
+++ b/pkg/yqlib/lib.go
@@ -28,37 +28,39 @@ type lib struct {
 
 func NewYqLib(l *logging.Logger) YqLib {
 	return &lib{
-		navigator: NewDataNavigator(l),
-		parser:    NewPathParser(),
-		log:       l,
+		parser: NewPathParser(),
+		log:    l,
 	}
 }
 
 func (l *lib) DebugNode(node *yaml.Node) {
-	l.navigator.DebugNode(node)
+	navigator := NewDataNavigator(l.log, false)
+	navigator.DebugNode(node)
 }
 
 func (l *lib) Get(rootNode *yaml.Node, path string) (*yaml.Node, error) {
 	var paths = l.parser.ParsePath(path)
-	return l.navigator.Get(rootNode, paths)
+	navigator := NewDataNavigator(l.log, true)
+	return navigator.Get(rootNode, paths)
 }
 
 func (l *lib) New(path string) yaml.Node {
 	var paths = l.parser.ParsePath(path)
-	newNode := yaml.Node{Kind: l.navigator.GuessKind(paths, 0)}
+	navigator := NewDataNavigator(l.log, false)
+	newNode := yaml.Node{Kind: navigator.GuessKind(paths, 0)}
 	return newNode
 }
 
 func (l *lib) Update(rootNode *yaml.Node, updateCommand UpdateCommand) error {
-	// later - support other command types
+	navigator := NewDataNavigator(l.log, false)
 	l.log.Debugf("%v to %v", updateCommand.Command, updateCommand.Path)
 	switch updateCommand.Command {
 	case "update":
 		var paths = l.parser.ParsePath(updateCommand.Path)
-		return l.navigator.Update(rootNode, paths, updateCommand.Value)
+		return navigator.Update(rootNode, paths, updateCommand.Value)
 	case "delete":
 		var paths = l.parser.ParsePath(updateCommand.Path)
-		return l.navigator.Delete(rootNode, paths)
+		return navigator.Delete(rootNode, paths)
 	default:
 		return fmt.Errorf("Unknown command %v", updateCommand.Command)
 	}