feat: add list of comparators in the selector page

docs/docs/concepts/selectors.mdx

@@ -1381,3 +1381,18 @@ flowchart TD
     class F parentSpan
     class G selectedSpan
 ```
+
+## Supported comparisons
+
+In previous examples, It was always used the equality comparator (`=`), however, the selector language supports a number of comparisons:
+
+| Operation     | Description                                                      |
+| :------------ | :--------------------------------------------------------------- |
+| `=`           | both values are equal                                            |
+| `!=`          | both values are different                                        |
+| `<`           | value on the left is less than the value on the right            |
+| `<=`          | value on the left is less or equal to the value on the right     |
+| `>`           | value on the left is greater than the value on the right         |
+| `>=`          | value on the left is greater or equal to the value on the right  |
+| `contains`    | string on the left contains the string on the right              |
+| `not-contains`| string on the left does not contain the string on the right      |

server/assertions/selectors/builder_test.go

@@ -39,6 +39,11 @@ func TestSimpleSelectorBuilder(t *testing.T) {
 			Expression:    "span.tracetest.span.type=\"http\"",
 			ShouldSucceed: false,
 		},
+		{
+			Name:          "Selector with invalid syntax",
+			Expression:    "span[attr.bool=true]",
+			ShouldSucceed: true,
+		},
 	}
 
 	for _, testCase := range testCases {

server/assertions/selectors/parser.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/alecthomas/participle/v2"
+	"github.com/alecthomas/participle/v2/lexer"
 )
 
 type ParserSelector struct {
@@ -18,14 +19,14 @@ type parserSpanSelector struct {
 
 type parserFilter struct {
 	Property string       `( @Ident ( @"." @Ident )*)`
-	Operator string       `@("=" | "contains" )`
+	Operator string       `@Comparator`
 	Value    *parserValue `@@*`
 }
 
 type parserValue struct {
 	String  *string  ` @String`
-	Int     *int64   ` | @Int`
 	Float   *float64 ` | @Float`
+	Int     *int64   ` | @Int`
 	Boolean *bool    ` | @("true" | "false")`
 }
 
@@ -34,8 +35,21 @@ type parserPseudoClass struct {
 	Value *parserValue `("(" @@* ")")*`
 }
 
+var languageLexer = lexer.MustStateful(lexer.Rules{
+	"Root": {
+		{Name: "whitespace", Pattern: `\s+`, Action: nil},
+		{Name: "Punc", Pattern: `[(),|\[\]:]`, Action: nil},
+
+		{Name: "Comparator", Pattern: `!=|<=|>=|=|<|>|contains|not-contains`},
+		{Name: "Ident", Pattern: `[a-zA-Z][a-zA-Z0-9_\.]*`, Action: nil},
+		{Name: "String", Pattern: `"(\\"|[^"])*"`, Action: nil},
+		{Name: "Float", Pattern: `[0-9]+\.[0-9]+`},
+		{Name: "Int", Pattern: `[0-9]+`},
+	},
+})
+
 func CreateParser() (*participle.Parser, error) {
-	parser, err := participle.Build(&ParserSelector{})
+	parser, err := participle.Build(&ParserSelector{}, participle.Lexer(languageLexer), participle.UseLookahead(2))
 	if err != nil {
 		return nil, fmt.Errorf("could not create parser: %w", err)
 	}

server/assertions/selectors/selector_test.go

@@ -142,6 +142,16 @@ func TestSelector(t *testing.T) {
 			Expression:      `span[kind="db"]`,
 			ExpectedSpanIds: []trace.SpanID{insertPokemonDatabaseSpanID, updatePokemonDatabaseSpanID},
 		},
+		{
+			Name:            "SelectorShouldMatchAllButDB",
+			Expression:      `span[kind!="db"]`,
+			ExpectedSpanIds: []trace.SpanID{postImportSpanID, getPokemonFromExternalAPISpanID},
+		},
+		{
+			Name:            "SelectorShouldGetSpansWithAttribute",
+			Expression:      `span[kind!=""]`,
+			ExpectedSpanIds: []trace.SpanID{postImportSpanID, insertPokemonDatabaseSpanID, getPokemonFromExternalAPISpanID, updatePokemonDatabaseSpanID},
+		},
 	}
 
 	for _, testCase := range testCases {