v4(toJSONSchema): Add multiple string pattern support (#4511)

* enhance string patterns

* fix other references

* use last added pattern

* apply code review suggestion

* nit

* remove extra imports

* Tweak

---------

Co-authored-by: Colin McDonnell <colinmcd94@gmail.com>

Author: samchungy

packages/zod/src/v4/classic/tests/json-schema.test.ts

@@ -368,6 +368,52 @@ describe("toJSONSchema", () => {
     `);
   });
 
+  test("string patterns", () => {
+    expect(z.toJSONSchema(z.string().startsWith("hello").includes("cruel").endsWith("world"))).toMatchInlineSnapshot(`
+      {
+        "$schema": "https://json-schema.org/draft/2020-12/schema",
+        "allOf": [
+          {
+            "pattern": "^hello.*",
+            "type": "string",
+          },
+          {
+            "pattern": "cruel",
+            "type": "string",
+          },
+          {
+            "pattern": ".*world$",
+            "type": "string",
+          },
+        ],
+      }
+    `);
+
+    expect(
+      z.toJSONSchema(
+        z
+          .string()
+          .regex(/^hello/)
+          .regex(/world$/)
+      )
+    ).toMatchInlineSnapshot(`
+      {
+        "$schema": "https://json-schema.org/draft/2020-12/schema",
+        "allOf": [
+          {
+            "format": "regex",
+            "pattern": "^hello",
+            "type": "string",
+          },
+          {
+            "pattern": "world$",
+            "type": "string",
+          },
+        ],
+      }
+    `);
+  });
+
   test("number constraints", () => {
     expect(z.toJSONSchema(z.number().min(5).max(10))).toMatchInlineSnapshot(
       `

packages/zod/src/v4/core/checks.ts

@@ -787,8 +787,12 @@ export const $ZodCheckStringFormat: core.$constructor<$ZodCheckStringFormat> = /
     $ZodCheck.init(inst, def);
 
     inst._zod.onattach.push((inst) => {
-      inst._zod.bag.format = def.format;
-      if (def.pattern) inst._zod.bag.pattern = def.pattern;
+      const bag = inst._zod.bag as schemas.$ZodStringInternals<unknown>["bag"];
+      bag.format = def.format;
+      if (def.pattern) {
+        bag.patterns ??= new Set();
+        bag.patterns.add(def.pattern);
+      }
     });
 
     inst._zod.check ??= (payload) => {
@@ -951,7 +955,9 @@ export const $ZodCheckIncludes: core.$constructor<$ZodCheckIncludes> = /*@__PURE
     const pattern = new RegExp(util.escapeRegex(def.includes));
     def.pattern = pattern;
     inst._zod.onattach.push((inst) => {
-      inst._zod.bag.pattern = pattern;
+      const bag = inst._zod.bag as schemas.$ZodStringInternals<unknown>["bag"];
+      bag.patterns ??= new Set();
+      bag.patterns.add(pattern);
     });
 
     inst._zod.check = (payload) => {
@@ -993,7 +999,9 @@ export const $ZodCheckStartsWith: core.$constructor<$ZodCheckStartsWith> = /*@__
     const pattern = new RegExp(`^${util.escapeRegex(def.prefix)}.*`);
     def.pattern ??= pattern;
     inst._zod.onattach.push((inst) => {
-      inst._zod.bag.pattern = pattern;
+      const bag = inst._zod.bag as schemas.$ZodStringInternals<unknown>["bag"];
+      bag.patterns ??= new Set();
+      bag.patterns.add(pattern);
     });
 
     inst._zod.check = (payload) => {
@@ -1035,7 +1043,9 @@ export const $ZodCheckEndsWith: core.$constructor<$ZodCheckEndsWith> = /*@__PURE
     const pattern = new RegExp(`.*${util.escapeRegex(def.suffix)}$`);
     def.pattern ??= pattern;
     inst._zod.onattach.push((inst) => {
-      inst._zod.bag.pattern = new RegExp(`.*${util.escapeRegex(def.suffix)}$`);
+      const bag = inst._zod.bag as schemas.$ZodStringInternals<unknown>["bag"];
+      bag.patterns ??= new Set();
+      bag.patterns.add(pattern);
     });
 
     inst._zod.check = (payload) => {

packages/zod/src/v4/core/schemas.ts

@@ -289,8 +289,9 @@ export interface $ZodStringInternals<Input> extends $ZodTypeInternals<string, In
   bag: util.LoosePartial<{
     minimum: number;
     maximum: number;
-    pattern: RegExp;
+    patterns: Set<RegExp>;
     format: string;
+    contentEncoding: string;
   }>;
 }
 
@@ -300,7 +301,7 @@ export interface $ZodString<Input = unknown> extends $ZodType {
 
 export const $ZodString: core.$constructor<$ZodString> = /*@__PURE__*/ core.$constructor("$ZodString", (inst, def) => {
   $ZodType.init(inst, def);
-  inst._zod.pattern = inst?._zod.bag?.pattern ?? regexes.string(inst._zod.bag);
+  inst._zod.pattern = [...(inst?._zod.bag?.patterns ?? [])].pop() ?? regexes.string(inst._zod.bag);
   inst._zod.parse = (payload, _) => {
     if (def.coerce)
       try {
@@ -675,7 +676,8 @@ export const $ZodIPv4: core.$constructor<$ZodIPv4> = /*@__PURE__*/ core.$constru
   def.pattern ??= regexes.ipv4;
   $ZodStringFormat.init(inst, def);
   inst._zod.onattach.push((inst) => {
-    inst._zod.bag.format = `ipv4`;
+    const bag = inst._zod.bag as $ZodStringInternals<unknown>["bag"];
+    bag.format = `ipv4`;
   });
 });
 
@@ -698,7 +700,8 @@ export const $ZodIPv6: core.$constructor<$ZodIPv6> = /*@__PURE__*/ core.$constru
   $ZodStringFormat.init(inst, def);
 
   inst._zod.onattach.push((inst) => {
-    inst._zod.bag.format = `ipv6`;
+    const bag = inst._zod.bag as $ZodStringInternals<unknown>["bag"];
+    bag.format = `ipv6`;
   });
 
   inst._zod.check = (payload) => {

packages/zod/src/v4/core/to-json-schema.ts

@@ -149,23 +149,31 @@ export class JSONSchemaGenerator {
         case "string": {
           const json: JSONSchema.StringSchema = _json as any;
           json.type = "string";
-          const { minimum, maximum, format, pattern, contentEncoding } = schema._zod.bag as {
-            minimum?: number;
-            maximum?: number;
-            format?: checks.$ZodStringFormats;
-            pattern?: RegExp;
-            contentEncoding?: string;
-          };
+          const { minimum, maximum, format, patterns, contentEncoding } = schema._zod
+            .bag as schemas.$ZodStringInternals<unknown>["bag"];
           if (typeof minimum === "number") json.minLength = minimum;
           if (typeof maximum === "number") json.maxLength = maximum;
           // custom pattern overrides format
           if (format) {
-            json.format = formatMap[format] ?? format;
-          }
-          if (pattern) {
-            json.pattern = pattern.source;
+            json.format = formatMap[format as checks.$ZodStringFormats] ?? format;
           }
           if (contentEncoding) json.contentEncoding = contentEncoding;
+          if (patterns) {
+            const regexes = [...patterns];
+            json.pattern = regexes[0].source;
+
+            if (regexes.length > 1) {
+              result.schema = {
+                allOf: [
+                  json,
+                  ...regexes.slice(1).map((regex) => ({
+                    type: "string",
+                    pattern: regex.source,
+                  })),
+                ],
+              };
+            }
+          }
 
           break;
         }