From 3f58c4bc38058a47d1e84f55bc2fd9d9bdf7eea5 Mon Sep 17 00:00:00 2001
From: Mike Farah <mikefarah@gmail.com>
Date: Wed, 6 Jan 2021 20:30:48 +1100
Subject: [PATCH] Can assign-update aliases and anchors

---
 pkg/yqlib/doc/Anchor and Alias Operators.md | 33 +++++++++++++
 pkg/yqlib/operator_anchors_aliases.go       | 54 ++++++++++++++++-----
 pkg/yqlib/operator_anchors_aliases_test.go  | 16 ++++++
 3 files changed, 90 insertions(+), 13 deletions(-)

diff --git a/pkg/yqlib/doc/Anchor and Alias Operators.md b/pkg/yqlib/doc/Anchor and Alias Operators.md
index b7a6c707..ea04f11e 100644
--- a/pkg/yqlib/doc/Anchor and Alias Operators.md	
+++ b/pkg/yqlib/doc/Anchor and Alias Operators.md	
@@ -31,6 +31,22 @@ will output
 a: &foobar cat
 ```
 
+## Set anchor relatively using assign-update
+Given a sample.yml file of:
+```yaml
+a:
+  b: cat
+```
+then
+```bash
+yq eval '.a anchor |= .b' sample.yml
+```
+will output
+```yaml
+a: &cat
+  b: cat
+```
+
 ## Get alias
 Given a sample.yml file of:
 ```yaml
@@ -62,6 +78,23 @@ b: &meow purr
 a: *meow
 ```
 
+## Set alias relatively using assign-update
+Given a sample.yml file of:
+```yaml
+b: &meow purr
+a:
+  f: meow
+```
+then
+```bash
+yq eval '.a alias |= .f' sample.yml
+```
+will output
+```yaml
+b: &meow purr
+a: *meow
+```
+
 ## Explode alias and anchor
 Given a sample.yml file of:
 ```yaml
diff --git a/pkg/yqlib/operator_anchors_aliases.go b/pkg/yqlib/operator_anchors_aliases.go
index d1ae0ea1..e558c222 100644
--- a/pkg/yqlib/operator_anchors_aliases.go
+++ b/pkg/yqlib/operator_anchors_aliases.go
@@ -3,20 +3,22 @@ package yqlib
 import (
 	"container/list"
 
-	"gopkg.in/yaml.v3"
+	yaml "gopkg.in/yaml.v3"
 )
 
 func AssignAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNode *PathTreeNode) (*list.List, error) {
 
 	log.Debugf("AssignAlias operator!")
 
-	rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
-	if err != nil {
-		return nil, err
-	}
 	aliasName := ""
-	if rhs.Front() != nil {
-		aliasName = rhs.Front().Value.(*CandidateNode).Node.Value
+	if !pathNode.Operation.UpdateAssign {
+		rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+		if err != nil {
+			return nil, err
+		}
+		if rhs.Front() != nil {
+			aliasName = rhs.Front().Value.(*CandidateNode).Node.Value
+		}
 	}
 
 	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
@@ -28,6 +30,17 @@ func AssignAliasOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNod
 	for el := lhs.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		log.Debugf("Setting aliasName : %v", candidate.GetKey())
+
+		if pathNode.Operation.UpdateAssign {
+			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+			if err != nil {
+				return nil, err
+			}
+			if rhs.Front() != nil {
+				aliasName = rhs.Front().Value.(*CandidateNode).Node.Value
+			}
+		}
+
 		candidate.Node.Kind = yaml.AliasNode
 		candidate.Node.Value = aliasName
 	}
@@ -51,13 +64,16 @@ func AssignAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNo
 
 	log.Debugf("AssignAnchor operator!")
 
-	rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
-	if err != nil {
-		return nil, err
-	}
 	anchorName := ""
-	if rhs.Front() != nil {
-		anchorName = rhs.Front().Value.(*CandidateNode).Node.Value
+	if !pathNode.Operation.UpdateAssign {
+		rhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Rhs)
+		if err != nil {
+			return nil, err
+		}
+
+		if rhs.Front() != nil {
+			anchorName = rhs.Front().Value.(*CandidateNode).Node.Value
+		}
 	}
 
 	lhs, err := d.GetMatchingNodes(matchingNodes, pathNode.Lhs)
@@ -69,6 +85,18 @@ func AssignAnchorOperator(d *dataTreeNavigator, matchingNodes *list.List, pathNo
 	for el := lhs.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 		log.Debugf("Setting anchorName of : %v", candidate.GetKey())
+
+		if pathNode.Operation.UpdateAssign {
+			rhs, err := d.GetMatchingNodes(nodeToMap(candidate), pathNode.Rhs)
+			if err != nil {
+				return nil, err
+			}
+
+			if rhs.Front() != nil {
+				anchorName = rhs.Front().Value.(*CandidateNode).Node.Value
+			}
+		}
+
 		candidate.Node.Anchor = anchorName
 	}
 	return matchingNodes, nil
diff --git a/pkg/yqlib/operator_anchors_aliases_test.go b/pkg/yqlib/operator_anchors_aliases_test.go
index 7cbde50a..2af815d3 100644
--- a/pkg/yqlib/operator_anchors_aliases_test.go
+++ b/pkg/yqlib/operator_anchors_aliases_test.go
@@ -21,6 +21,14 @@ var anchorOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::a: &foobar cat\n",
 		},
 	},
+	{
+		description: "Set anchor relatively using assign-update",
+		document:    `a: {b: cat}`,
+		expression:  `.a anchor |= .b`,
+		expected: []string{
+			"D0, P[], (doc)::a: &cat {b: cat}\n",
+		},
+	},
 	{
 		description: "Get alias",
 		document:    `{b: &billyBob meow, a: *billyBob}`,
@@ -37,6 +45,14 @@ var anchorOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::{b: &meow purr, a: *meow}\n",
 		},
 	},
+	{
+		description: "Set alias relatively using assign-update",
+		document:    `{b: &meow purr, a: {f: meow}}`,
+		expression:  `.a alias |= .f`,
+		expected: []string{
+			"D0, P[], (doc)::{b: &meow purr, a: *meow}\n",
+		},
+	},
 	{
 		description: "Explode alias and anchor",
 		document:    `{f : {a: &a cat, b: *a}}`,