add generator logic and tests

Signed-off-by: Kartikay <kartikay_2101ce32@iitp.ac.in>

Author: kartikaysaxena

pkg/schemadsl/compiler/compiler.go

@@ -91,7 +91,7 @@ func DisallowExpirationFlag() Option {
 
 func DisallowDeprecationFlag() Option {
 	return func(cfg *config) {
-		cfg.allowedFlags = lo.Filter(cfg.allowedFlags, func(s string, _ int) bool {
+		cfg.allowedFlags = slicez.Filter(cfg.allowedFlags, func(s string) bool {
 			return s != deprecationFlag
 		})
 	}

pkg/schemadsl/generator/generator.go

@@ -202,6 +202,20 @@ func (sg *sourceGenerator) emitNamespace(namespace *core.NamespaceDefinition) er
 	sg.markNewScope()
 
 	for _, relation := range namespace.Relation {
+		if relation.DeprecationType != core.DeprecationType_DEPRECATED_TYPE_UNSPECIFIED {
+			sg.flags.Add("deprecation")
+			sg.append("@deprecated(")
+
+			switch relation.DeprecationType {
+			case core.DeprecationType_DEPRECATED_TYPE_WARNING:
+				sg.append("warn")
+			case core.DeprecationType_DEPRECATED_TYPE_ERROR:
+				sg.append("error")
+			}
+			sg.append(")")
+			sg.appendLine()
+		}
+
 		err := sg.emitRelation(relation)
 		if err != nil {
 			return err

pkg/schemadsl/generator/generator_test.go

@@ -395,6 +395,38 @@ definition document {
 	relation viewer: user
 }`,
 		},
+		{
+			"deprecation test",
+			`use deprecation
+
+			definition document {
+
+				@deprecated(warn)
+				relation viewer: user
+				
+				@deprecated(error)
+				relation editor: user
+			}`,
+			`use deprecation
+
+definition document {
+	@deprecated(warn)
+	relation viewer: user
+	@deprecated(error)
+	relation editor: user
+}`,
+		},
+		{
+			"unused deprecation flag",
+			`use deprecation
+			
+			definition document{
+				relation viewer: user
+		}`,
+			`definition document {
+	relation viewer: user
+}`,
+		},
 	}
 
 	for _, test := range tests {

pkg/schemadsl/lexer/flags.go

@@ -13,6 +13,10 @@ const (
 	// FlagTypeChecking indicates that `typechecking` is supported as a first-class
 	// feature in the schema.
 	FlagTypeChecking = "typechecking"
+
+	// FlagDeprecation indicates that `deprecation` is supported as a first-class
+	// feature in the schema.
+	FlagDeprecation = "deprecation"
 )
 
 var AllUseFlags []string
@@ -22,9 +26,6 @@ func init() {
 	slices.Sort(AllUseFlags)
 }
 
-// Deprecation Flag
-const FlagDeprecation = "deprecation"
-
 type transformer func(lexeme Lexeme) (Lexeme, bool)
 
 // Flags is a map of flag names to their corresponding transformers.
@@ -44,6 +45,16 @@ var Flags = map[string]transformer{
 
 		return lexeme, false
 	},
+
+	FlagDeprecation: func(lexeme Lexeme) (Lexeme, bool) {
+		if lexeme.Kind == TokenTypeIdentifier && lexeme.Value == "deprecation" {
+			lexeme.Kind = TokenTypeKeyword
+			return lexeme, true
+		}
+
+		return lexeme, false
+	},
+
 	FlagTypeChecking: func(lexeme Lexeme) (Lexeme, bool) {
 		// `typechecking` becomes a keyword.
 		if lexeme.Kind == TokenTypeIdentifier && lexeme.Value == "typechecking" {