[cli] Show rich diffs for JSON/YAML objects/arrays (#9380)

When displaying a diff between textual values, first try to decode the
old and new values as JSON and YAML. If both values decode successfully,
render the diff between the decoded values rather than the diff between
the text.

Fixes #5831.

CHANGELOG_PENDING.md

@@ -15,6 +15,9 @@
 - [cli] Display richer diffs for texutal property values.
   [#9376](https://github.com/pulumi/pulumi/pull/9376)
 
+- [cli] Display richer diffs for JSON/YAML property values.
+  [#9380](https://github.com/pulumi/pulumi/pull/9380)
+
 ### Bug Fixes
 
 - [codegen/node] - Fix an issue with escaping deprecation messages.

pkg/backend/display/object_diff.go

@@ -16,6 +16,7 @@ package display
 
 import (
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"io"
 	"reflect"
@@ -24,6 +25,7 @@ import (
 	"strings"
 
 	"github.com/sergi/go-diff/diffmatchpatch"
+	"gopkg.in/yaml.v3"
 
 	"github.com/pulumi/pulumi/pkg/v3/engine"
 	"github.com/pulumi/pulumi/pkg/v3/resource/deploy"
@@ -1042,6 +1044,10 @@ func escape(s string) string {
 }
 
 func (p *propertyPrinter) printTextDiff(old, new string) {
+	if p.printEncodedValueDiff(old, new) {
+		return
+	}
+
 	differ := diffmatchpatch.New()
 	differ.DiffTimeout = 0
 
@@ -1152,3 +1158,57 @@ func (p *propertyPrinter) printLineDiff(diffs []diffmatchpatch.Diff) {
 		}
 	}
 }
+
+func (p *propertyPrinter) printEncodedValueDiff(old, new string) bool {
+	oldValue, oldKind, ok := p.decodeValue(old)
+	if !ok {
+		return false
+	}
+
+	newValue, newKind, ok := p.decodeValue(new)
+	if !ok {
+		return false
+	}
+
+	if oldKind == newKind {
+		p.write("(%s) ", oldKind)
+	} else {
+		p.write("(%s => %s) ", oldKind, newKind)
+	}
+
+	diff := oldValue.Diff(newValue, resource.IsInternalPropertyKey)
+	if diff == nil {
+		p.withOp(deploy.OpSame).printPropertyValue(oldValue)
+		return true
+	}
+
+	p.printPropertyValueDiff(func(*propertyPrinter) {}, *diff)
+	return true
+}
+
+func (p *propertyPrinter) decodeValue(repr string) (resource.PropertyValue, string, bool) {
+	decode := func() (interface{}, string, bool) {
+		r := strings.NewReader(repr)
+
+		var object interface{}
+		if err := json.NewDecoder(r).Decode(&object); err == nil {
+			return object, "json", true
+		}
+
+		r.Reset(repr)
+		if err := yaml.NewDecoder(r).Decode(&object); err == nil {
+			return object, "yaml", true
+		}
+
+		return nil, "", false
+	}
+
+	object, kind, ok := decode()
+	if ok {
+		switch object.(type) {
+		case []interface{}, map[string]interface{}:
+			return resource.NewPropertyValue(object), kind, true
+		}
+	}
+	return resource.PropertyValue{}, "", false
+}