feat: support contains to compare json objects (#3687)

* feat: support `contains` to compare json objects

* add test for json in span attribute

* add suggested tests by Daniel

* add doc

* add test with deep comparison with arrays

* Update docs/docs/concepts/expressions.mdx

Co-authored-by: Julianne Fermi <julianne@kubeshop.io>

---------

Co-authored-by: Julianne Fermi <julianne@kubeshop.io>

docs/docs/concepts/expressions.mdx

@@ -21,6 +21,7 @@ Tracetest allows you to add expressions when writing your tests. They are a nice
 * Arithmetic operations
 * String interpolation
 * Filters
+* JSON comparison
 
 ### Reference Span Attributes
 
@@ -139,3 +140,26 @@ attr:myapp.operations | get_index 2 | type = "string"
 # check if attribute is either a number of a string
 ["number", "string"] contains attr:my_attribute | type
 ```
+
+### JSON Comparison
+
+When working with APIs, it's very common for developers to check if the response contains data while ignoring all the noise a response can have. For this, you can use the `contains` comparator in JSON objects. It works just like [Jest's toMatchObject](https://jestjs.io/pt-BR/docs/expect#tomatchobjectobject).
+
+The order of the attributes doesn't matter and the left side of the expression can contain more attributes than the right side.
+
+Some examples:
+
+```css
+# If user is 32 years old, it passes
+'{"name": "john", "age": 32}' contains '{"age": 32}'
+```
+
+```css
+# If any of the users is called "maria", it passes
+'[{"name": "john", "age": 32}, {"name": "maria", "age": 63}]' contains '{"name": "maria"}'
+```
+
+```css
+# In this case, both ages must be part of the JSON array
+'[{"name": "john", "age": 32}, {"name": "maria", "age": 63}]' contains '[{"age": 63}, {"age": 32}]'
+```

server/assertions/comparator/basic.go

@@ -1,6 +1,7 @@
 package comparator
 
 import (
+	"encoding/json"
 	"fmt"
 	"strconv"
 	"strings"
@@ -18,6 +19,7 @@ var (
 		NotContains,
 		StartsWith,
 		EndsWith,
+		JsonContains,
 	}
 )
 
@@ -228,3 +230,101 @@ func (c endsWith) Compare(expected, actual string) error {
 func (c endsWith) String() string {
 	return "endsWith"
 }
+
+// JsonContains
+var JsonContains Comparator = jsonContains{}
+
+type jsonContains struct{}
+
+func (c jsonContains) Compare(right, left string) error {
+	supersetMap, err := c.parseJson(left)
+	if err != nil {
+		return fmt.Errorf("left side is not a JSON object")
+	}
+
+	subsetMap, err := c.parseJson(right)
+	if err != nil {
+		return fmt.Errorf("left side is not a JSON object")
+	}
+
+	return c.compare(supersetMap, subsetMap)
+}
+
+func (c jsonContains) parseJson(input string) ([]map[string]any, error) {
+	if strings.HasPrefix(input, "[") && strings.HasSuffix(input, "]") {
+		output := []map[string]any{}
+		err := json.Unmarshal([]byte(input), &output)
+		if err != nil {
+			return []map[string]any{}, fmt.Errorf("invalid JSON array")
+		}
+
+		return output, nil
+	}
+
+	object := map[string]any{}
+	err := json.Unmarshal([]byte(input), &object)
+	if err != nil {
+		return []map[string]any{}, fmt.Errorf("invalid JSON object")
+	}
+
+	return []map[string]any{object}, nil
+}
+
+func (c jsonContains) compare(left, right []map[string]any) error {
+	for i, expected := range right {
+		err := c.anyMatches(left, expected)
+		if err != nil {
+			return fmt.Errorf("left side array doesn't match item %d of right side: %w", i, ErrNoMatch)
+		}
+	}
+
+	return nil
+}
+
+func (c jsonContains) anyMatches(array []map[string]any, expected map[string]any) error {
+	for _, left := range array {
+		err := c.compareObjects(left, expected)
+		if err == nil {
+			return nil
+		}
+	}
+
+	return ErrNoMatch
+}
+
+func (c jsonContains) compareObjects(left, right map[string]any) error {
+	for key, value := range right {
+		leftValue, ok := left[key]
+		if !ok {
+			return fmt.Errorf(`field "%s" not found on left side: %w`, key, ErrNoMatch)
+		}
+
+		if leftValueMap, ok := leftValue.(map[string]any); ok {
+			rightValueMap, ok := value.(map[string]any)
+			if !ok {
+				return fmt.Errorf(`field: "%s": %w`, key, ErrWrongType)
+			}
+
+			err := c.compareObjects(leftValueMap, rightValueMap)
+			if err != nil {
+				return fmt.Errorf(`field "%s": %w`, key, err)
+			}
+
+			return nil
+		}
+
+		// This minimizes the change of a panic due to comparing two []interface{} types
+		leftValueString, _ := json.Marshal(leftValue)
+		rightValueString, _ := json.Marshal(value)
+
+		if string(leftValueString) != string(rightValueString) {
+			return fmt.Errorf(`field "%s": %w`, key, ErrNoMatch)
+		}
+	}
+
+	return nil
+}
+
+func (c jsonContains) String() string {
+	return "json-contains"
+}

server/assertions/comparator/comparators.go

@@ -8,8 +8,9 @@ type Comparator interface {
 }
 
 var (
-	ErrNoMatch  = fmt.Errorf("no match")
-	ErrNotFound = fmt.Errorf("not found")
+	ErrNoMatch   = fmt.Errorf("no match")
+	ErrNotFound  = fmt.Errorf("not found")
+	ErrWrongType = fmt.Errorf("wrong type")
 )
 
 type Registry interface {

server/expression/comparison.go

@@ -4,10 +4,17 @@ import (
 	"fmt"
 
 	"github.com/kubeshop/tracetest/server/assertions/comparator"
+	"github.com/kubeshop/tracetest/server/expression/types"
 	"github.com/kubeshop/tracetest/server/expression/value"
 )
 
 func compare(comparatorName string, leftValue, rightValue value.Value) error {
+	if rightValue.Value().Type == types.TypeJson && comparatorName == "contains" {
+		if leftValue.Value().Type == types.TypeJson || leftValue.Value().Type == types.TypeArray {
+			comparatorName = "json-contains"
+		}
+	}
+
 	comparatorFunction, err := comparator.DefaultRegistry().Get(comparatorName)
 	if err != nil {
 		return fmt.Errorf("comparator not supported: %w", err)
@@ -17,12 +24,7 @@ func compare(comparatorName string, leftValue, rightValue value.Value) error {
 		return compareArrayContains(leftValue, rightValue)
 	}
 
-	err = comparatorFunction.Compare(rightValue.String(), leftValue.String())
-	if err == comparator.ErrNoMatch {
-		return ErrNoMatch
-	}
-
-	return nil
+	return comparatorFunction.Compare(rightValue.String(), leftValue.String())
 }
 
 func compareArrayContains(array, expected value.Value) error {

server/expression/executor_test.go

@@ -373,6 +373,74 @@ func TestArrayExecution(t *testing.T) {
 			Query:      `[31,35,39] contains 42`,
 			ShouldPass: false,
 		},
+		{
+			Name:       "should_identify_array_instead_of_json",
+			Query:      `["{}", "{}", "{}"] | type = "array"`,
+			ShouldPass: true,
+		},
+	}
+
+	executeTestCases(t, testCases)
+}
+
+func TestJSONExecution(t *testing.T) {
+	testCases := []executorTestCase{
+		{
+			Name:       "should_identify_json_input",
+			Query:      `'{"name": "john", "age": 32, "email": "john@company.com"}' | type = "json"`,
+			ShouldPass: true,
+		},
+		{
+			Name:       "should_be_able_to_compare_with_subset",
+			Query:      `'{"name": "john", "age": 32, "email": "john@company.com"}' contains '{"email": "john@company.com", "name": "john"}'`,
+			ShouldPass: true,
+		},
+		{
+			Name:       "should_be_able_to_compare_with_subset_ignoring_order",
+			Query:      `'{"name": "john", "age": 32, "email": "john@company.com"}' contains '{"email": "john@company.com", "name": "john", "age": 32}'`,
+			ShouldPass: true,
+		},
+		{
+			Name:       "should_be_able_to_compare_deep_objects_in_subset",
+			Query:      `'{"name": "john", "age": 32, "email": "john@company.com", "company": {"name": "Company", "address": "1234 Agora Street"}}' contains '{"email": "john@company.com", "name": "john", "company": {"name": "Company"}}'`,
+			ShouldPass: true,
+		},
+		{
+			Name:       "should_be_able_to_compare_array_of_json_objects",
+			Query:      `'[{"name": "john", "age": 32}, {"name": "Maria", "age": 63}]' contains '[{"age": 63}, {"age": 32}]'`,
+			ShouldPass: true,
+		},
+		{
+			Name:       "should_match_complete_arrays",
+			Query:      `'{"numbers": [0,1,2,3,4]}' contains '{"numbers": [0,1,2,3,4]}'`,
+			ShouldPass: true,
+		},
+		{
+			Name:       "should_fail_when_array_doesnt_match_size_and_order",
+			Query:      `'{"numbers": [0,1,2,3,4]}' contains '{"numbers": [0,1]}'`,
+			ShouldPass: false,
+		},
+		{
+			Name:       "should_fail_when_array_contains_same_elements_but_different_types",
+			Query:      `'{"numbers": [0,1,2,3,4]}' contains '{"numbers": [0,1,"2","3",4]}'`,
+			ShouldPass: false,
+		},
+		{
+			Name:       "should_be_able_to_compare_deep_objects_with_arrays_in_subset",
+			Query:      `'{"name": "john", "age": 32, "email": "john@company.com", "company": {"name": "Company", "address": "1234 Agora Street", "telephones": ["01", "02", "03"]}}' contains '{"email": "john@company.com", "name": "john", "company": {"name": "Company", "telephones": ["01", "02", "03"]}}'`,
+			ShouldPass: true,
+		},
+		{
+			Name:       "should_identify_json_input_from_attribute",
+			Query:      `attr:tracetest.response.body contains '{"name": "john"}'`,
+			ShouldPass: true,
+			AttributeDataStore: expression.AttributeDataStore{
+				Span: traces.Span{
+					ID:         id.NewRandGenerator().SpanID(),
+					Attributes: traces.NewAttributes().Set("tracetest.response.body", `{"name": "john", "age": 32, "email": "john@company.com"}`),
+				},
+			},
+		},
 	}
 
 	executeTestCases(t, testCases)

server/expression/types/types.go

@@ -1,6 +1,9 @@
 package types
 
-import "regexp"
+import (
+	"encoding/json"
+	"regexp"
+)
 
 type Type uint
 
@@ -12,11 +15,13 @@ const (
 	TypeDuration
 	TypeVariable
 	TypeArray
+	TypeJson
 )
 
 var typeNames = map[Type]string{
 	TypeNil:       "nil",
 	TypeString:    "string",
+	TypeJson:      "json",
 	TypeNumber:    "number",
 	TypeAttribute: "attribute",
 	TypeDuration:  "duration",
@@ -37,7 +42,16 @@ func GetType(value string) Type {
 		return TypeDuration
 	}
 
+	if err := json.Unmarshal([]byte(value), &map[string]any{}); err == nil {
+		return TypeJson
+	}
+
 	if arrayRegex.Match([]byte(value)) {
+		var jsonArray = []map[string]any{}
+		if err := json.Unmarshal([]byte(value), &jsonArray); err == nil {
+			return TypeJson
+		}
+
 		return TypeArray
 	}
 

server/traces/span_entitiess.go

@@ -108,10 +108,12 @@ func (a Attributes) Get(key string) string {
 	return v
 }
 
-func (a Attributes) Set(key, value string) {
+func (a Attributes) Set(key, value string) Attributes {
 	a.lock()
 	defer a.unlock()
 	a.values[key] = value
+
+	return a
 }
 
 func (a Attributes) Delete(key string) {