feat(no-base-to-string): add checkUnknown option (#533)

refs oxc-project/oxc#16978 typescript-eslint/typescript-eslint#11128

Author: camc314

internal/rules/no_base_to_string/no_base_to_string.go

@@ -194,6 +194,9 @@ var NoBaseToStringRule = rule.Rule{
 					return collectToStringCertainty(constraint, visited)
 				}
 				// unconstrained generic means `unknown`
+				if opts.CheckUnknown {
+					return usefulnessSometimes
+				}
 				return usefulnessAlways
 			}
 
@@ -231,7 +234,11 @@ var NoBaseToStringRule = rule.Rule{
 				toString = checker.Checker_getPropertyOfType(ctx.TypeChecker, t, "toLocaleString")
 			}
 			if toString == nil {
-				// e.g. any/unknown
+				// unknown
+				if opts.CheckUnknown && utils.IsTypeFlagSet(t, checker.TypeFlagsUnknown) {
+					return usefulnessSometimes
+				}
+				// e.g. any
 				return usefulnessAlways
 			}
 

internal/rules/no_base_to_string/no_base_to_string_test.go

@@ -487,15 +487,6 @@ declare const bb: ExtendedGuildChannel;
 bb.toString();
     `},
 			{Code: `
-function foo<T>(x: T) {
-  String(x);
-}
-    `},
-			{Code: `
-declare const u: unknown;
-String(u);
-    `},
-			{Code: `
 type Value = string | Value[];
 declare const v: Value;
 
@@ -523,7 +514,109 @@ String(v);
 declare const v: ('foo' | 'bar')[][];
 String(v);
     `},
+			// unknown type - valid by default (checkUnknown: false)
+			{Code: "declare const x: unknown;\n`${x})`;\n"},
+			{Code: "declare const x: unknown;\nx.toString();\n"},
+			{Code: "declare const x: unknown;\nx.toLocaleString();\n"},
+			{Code: "declare const x: unknown;\n'' + x;\n"},
+			{Code: "declare const x: unknown;\nString(x);\n"},
+			{Code: "declare const x: unknown;\n'' += x;\n"},
+			// unconstrained generic - valid by default (checkUnknown: false)
+			{Code: "function foo<T>(x: T) {\n  String(x);\n}\n"},
+			// any type - always valid
+			{Code: "declare const x: any;\n`${x})`;\n"},
+			{Code: "declare const x: any;\nx.toString();\n"},
+			{Code: "declare const x: any;\nx.toLocaleString();\n"},
+			{Code: "declare const x: any;\n'' + x;\n"},
+			{Code: "declare const x: any;\nString(x);\n"},
+			{Code: "declare const x: any;\n'' += x;\n"},
 		}), []rule_tester.InvalidTestCase{
+		// Tests with checkUnknown: true
+		{
+			Code: `
+declare const x: unknown;
+` + "`" + `${x})` + "`" + `;
+      `,
+			Options: NoBaseToStringOptions{CheckUnknown: true},
+			Errors: []rule_tester.InvalidTestCaseError{
+				{
+					MessageId: "baseToString",
+				},
+			},
+		},
+		{
+			Code: `
+declare const x: unknown;
+x.toString();
+      `,
+			Options: NoBaseToStringOptions{CheckUnknown: true},
+			Errors: []rule_tester.InvalidTestCaseError{
+				{
+					MessageId: "baseToString",
+				},
+			},
+		},
+		{
+			Code: `
+declare const x: unknown;
+x.toLocaleString();
+      `,
+			Options: NoBaseToStringOptions{CheckUnknown: true},
+			Errors: []rule_tester.InvalidTestCaseError{
+				{
+					MessageId: "baseToString",
+				},
+			},
+		},
+		{
+			Code: `
+declare const x: unknown;
+'' + x;
+      `,
+			Options: NoBaseToStringOptions{CheckUnknown: true},
+			Errors: []rule_tester.InvalidTestCaseError{
+				{
+					MessageId: "baseToString",
+				},
+			},
+		},
+		{
+			Code: `
+declare const x: unknown;
+String(x);
+      `,
+			Options: NoBaseToStringOptions{CheckUnknown: true},
+			Errors: []rule_tester.InvalidTestCaseError{
+				{
+					MessageId: "baseToString",
+				},
+			},
+		},
+		{
+			Code: `
+declare const x: unknown;
+'' += x;
+      `,
+			Options: NoBaseToStringOptions{CheckUnknown: true},
+			Errors: []rule_tester.InvalidTestCaseError{
+				{
+					MessageId: "baseToString",
+				},
+			},
+		},
+		{
+			Code: `
+function foo<T>(x: T) {
+  String(x);
+}
+      `,
+			Options: NoBaseToStringOptions{CheckUnknown: true},
+			Errors: []rule_tester.InvalidTestCaseError{
+				{
+					MessageId: "baseToString",
+				},
+			},
+		},
 		{
 			Code: "`${{}})`;",
 			Errors: []rule_tester.InvalidTestCaseError{

internal/rules/no_base_to_string/options.go

@@ -4,6 +4,11 @@
     "no_base_to_string_options": {
       "type": "object",
       "properties": {
+        "checkUnknown": {
+          "type": "boolean",
+          "description": "Whether to also check values of type `unknown`.",
+          "default": false
+        },
         "ignoredTypeNames": {
           "type": "array",
           "items": {