feat: remix optional segments

.changeset/moody-pants-own.md

@@ -0,0 +1,25 @@
+---
+"@remix-run/dev": minor
+---
+
+feat: remix optional segments  
+
+Allows for the creation of optional route segments by using parenthesis. For example:
+Creating the following file routes in remix `/($lang)/about`
+this will match the following routes 
+```
+/en/about
+/fr/about
+/about
+```
+
+helpful for optional language paths.
+
+Another example `/(one)/($two)/(three).($four)` file routing would match
+```
+/
+/one
+/one/param1
+/one/param1/three
+/one/param1/three/param2
+```

contributors.yml

@@ -253,6 +253,7 @@
 - lili21
 - lionotm
 - liranm
+- lordofthecactus
 - lpsinger
 - lswest
 - lucasdibz

packages/remix-dev/__tests__/routesConvention-test.ts

@@ -36,12 +36,68 @@ describe("createRoutePath", () => {
       ["[index]", "index"],
       ["test/inde[x]", "test/index"],
       ["[i]ndex/[[].[[]]", "index/[/[]"],
+
+      // Optional segment routes
+      ["(routes)/$", "routes?/*"],
+      ["(routes)/(sub)/$", "routes?/sub?/*"],
+      ["(routes).(sub)/$", "routes?/sub?/*"],
+      ["(routes)/($slug)", "routes?/:slug?"],
+      ["(routes)/sub/($slug)", "routes?/sub/:slug?"],
+      ["(routes).sub/($slug)", "routes?/sub/:slug?"],
+      ["(nested)/$", "nested?/*"],
+      ["(flat).$", "flat?/*"],
+      ["($slug)", ":slug?"],
+      ["(nested)/($slug)", "nested?/:slug?"],
+      ["(flat).($slug)", "flat?/:slug?"],
+      ["flat.(sub)", "flat/sub?"],
+      ["__layout/(test)", "test?"],
+      ["__layout.(test)", "test?"],
+      ["__layout/($slug)", ":slug?"],
+      ["(nested)/__layout/($slug)", "nested?/:slug?"],
+      ["($slug[.]json)", ":slug.json?"],
+      ["(sub)/([sitemap.xml])", "sub?/sitemap.xml?"],
+      ["(sub)/[(sitemap.xml)]", "sub?/(sitemap.xml)"],
+      ["(posts)/($slug)/([image.jpg])", "posts?/:slug?/image.jpg?"],
+      [
+        "($[$dollabills]).([.]lol)[/](what)/([$]).$",
+        ":$dollabills?/.lol)/(what?/$?/*",
+      ],
+      [
+        "($[$dollabills]).([.]lol)/(what)/([$]).($up)",
+        ":$dollabills?/.lol?/what?/$?/:up?",
+      ],
+      ["(sub).([[])", "sub?/[?"],
+      ["(sub).(])", "sub?/]?"],
+      ["(sub).([[]])", "sub?/[]?"],
+      ["(sub).([[])", "sub?/[?"],
+      ["(beef])", "beef]?"],
+      ["([index])", "index?"],
+      ["(test)/(inde[x])", "test?/index?"],
+      ["([i]ndex)/([[]).([[]])", "index?/[?/[]?"],
     ];
 
     for (let [input, expected] of tests) {
       it(`"${input}" -> "${expected}"`, () => {
         expect(createRoutePath(input)).toBe(expected);
       });
     }
+
+    describe("optional segments", () => {
+      it("will only work when starting and ending a segment with parenthesis", () => {
+        let [input, expected] = ["(routes.sub)/$", "(routes/sub)/*"];
+        expect(createRoutePath(input)).toBe(expected);
+      });
+
+      it("throws error on optional to splat routes", () => {
+        expect(() => createRoutePath("(routes)/($)")).toThrow("Splat");
+        expect(() => createRoutePath("($)")).toThrow("Splat");
+      });
+
+      it("throws errors on optional index without brackets routes", () => {
+        expect(() => createRoutePath("(nested)/(index)")).toThrow("index");
+        expect(() => createRoutePath("(flat).(index)")).toThrow("index");
+        expect(() => createRoutePath("(index)")).toThrow("index");
+      });
+    });
   });
 });

packages/remix-dev/config/routesConvention.ts

@@ -112,12 +112,17 @@ export function defineConventionalRoutes(
 let escapeStart = "[";
 let escapeEnd = "]";
 
+let optionalStart = "(";
+let optionalEnd = ")";
+
 // TODO: Cleanup and write some tests for this function
 export function createRoutePath(partialRouteId: string): string | undefined {
   let result = "";
   let rawSegmentBuffer = "";
 
   let inEscapeSequence = 0;
+  let inOptionalSegment = 0;
+  let optionalSegmentIndex = null;
   let skipSegment = false;
   for (let i = 0; i < partialRouteId.length; i++) {
     let char = partialRouteId.charAt(i);
@@ -139,8 +144,34 @@ export function createRoutePath(partialRouteId: string): string | undefined {
       return char === "_" && nextChar === "_" && !rawSegmentBuffer;
     }
 
+    function isSegmentSeparator(checkChar = char) {
+      return (
+        checkChar === "/" || checkChar === "." || checkChar === path.win32.sep
+      );
+    }
+
+    function isNewOptionalSegment() {
+      return (
+        char === optionalStart &&
+        lastChar !== optionalStart &&
+        (isSegmentSeparator(lastChar) || lastChar === undefined) &&
+        !inOptionalSegment &&
+        !inEscapeSequence
+      );
+    }
+
+    function isCloseOptionalSegment() {
+      return (
+        char === optionalEnd &&
+        nextChar !== optionalEnd &&
+        (isSegmentSeparator(nextChar) || nextChar === undefined) &&
+        inOptionalSegment &&
+        !inEscapeSequence
+      );
+    }
+
     if (skipSegment) {
-      if (char === "/" || char === "." || char === path.win32.sep) {
+      if (isSegmentSeparator()) {
         skipSegment = false;
       }
       continue;
@@ -156,18 +187,40 @@ export function createRoutePath(partialRouteId: string): string | undefined {
       continue;
     }
 
+    if (isNewOptionalSegment()) {
+      inOptionalSegment++;
+      optionalSegmentIndex = result.length;
+      result += "(";
+      continue;
+    }
+
+    if (isCloseOptionalSegment()) {
+      if (optionalSegmentIndex !== null) {
+        result =
+          result.slice(0, optionalSegmentIndex) +
+          result.slice(optionalSegmentIndex + 1);
+      }
+      optionalSegmentIndex = null;
+      inOptionalSegment--;
+      result += "?";
+      continue;
+    }
+
     if (inEscapeSequence) {
       result += char;
       continue;
     }
 
-    if (char === "/" || char === path.win32.sep || char === ".") {
+    if (isSegmentSeparator()) {
       if (rawSegmentBuffer === "index" && result.endsWith("index")) {
         result = result.replace(/\/?index$/, "");
       } else {
         result += "/";
       }
+
       rawSegmentBuffer = "";
+      inOptionalSegment = 0;
+      optionalSegmentIndex = null;
       continue;
     }
 
@@ -179,6 +232,11 @@ export function createRoutePath(partialRouteId: string): string | undefined {
     rawSegmentBuffer += char;
 
     if (char === "$") {
+      if (nextChar === ")") {
+        throw new Error(
+          `Invalid route path: ${partialRouteId}. Splat route $ is already optional`
+        );
+      }
       result += typeof nextChar === "undefined" ? "*" : ":";
       continue;
     }
@@ -190,6 +248,12 @@ export function createRoutePath(partialRouteId: string): string | undefined {
     result = result.replace(/\/?index$/, "");
   }
 
+  if (rawSegmentBuffer === "index" && result.endsWith("index?")) {
+    throw new Error(
+      `Invalid route path: ${partialRouteId}. Make index route optional by using [index]`
+    );
+  }
+
   return result || undefined;
 }