[added] formatPattern util method

Author: mjackson

modules/URLUtils.js

@@ -1,4 +1,5 @@
 import qs from 'qs';
+import invariant from 'invariant';
 
 export var parseQueryString = qs.parse;
 
@@ -134,3 +135,52 @@ export function matchPattern(pattern, pathname) {
 export function getParamNames(pattern) {
   return compilePattern(pattern).paramNames;
 }
+
+/**
+ * Returns a version of the given pattern with params interpolated. Throws
+ * if there is a dynamic segment of the pattern for which there is no param.
+ */
+export function formatPattern(pattern, params) {
+  params = params || {};
+
+  var { tokens } = compilePattern(pattern);
+  var parenCount = 0, pathname = '', splatIndex = 0;
+
+  var token, paramName, paramValue;
+  for (var i = 0, len = tokens.length; i < len; ++i) {
+    token = tokens[i];
+
+    if (token === '*') {
+      paramValue = Array.isArray(params.splat) ? params.splat[splatIndex++] : params.splat;
+
+      invariant(
+        paramValue != null || parenCount > 0,
+        'Missing splat #%s for path "%s"',
+        splatIndex, pattern
+      );
+
+      if (paramValue != null)
+        pathname += paramValue;
+    } else if (token === '(') {
+      parenCount += 1;
+    } else if (token === ')') {
+      parenCount -= 1;
+    } else if (token.charAt(0) === ':') {
+      paramName = token.substring(1);
+      paramValue = params[paramName];
+
+      invariant(
+        paramValue != null || parenCount > 0,
+        'Missing "%s" parameter for path "%s"',
+        paramName, pattern
+      );
+
+      if (paramValue != null)
+        pathname += paramValue;
+    } else {
+      pathname += token;
+    }
+  }
+
+  return pathname.replace(/\/+/g, '/');
+}

modules/__tests__/URLUtils-test.js

@@ -1,5 +1,5 @@
 import expect from 'expect';
-import { getPathname, getQueryString } from '../URLUtils';
+import { getPathname, getQueryString, formatPattern } from '../URLUtils';
 
 describe('getPathname', function () {
   it('returns the pathname portion of a path', function () {
@@ -16,3 +16,101 @@ describe('getQueryString', function () {
 describe('matchPattern', function () {
   it('ignores trailing slashes');
 });
+
+describe('formatPattern', function () {
+  describe('when a pattern does not have dynamic segments', function () {
+    var pattern = 'a/b/c';
+
+    it('returns the pattern', function () {
+      expect(formatPattern(pattern, {})).toEqual(pattern);
+    });
+  });
+
+  describe('when a pattern has dynamic segments', function () {
+    var pattern = 'comments/:id/edit';
+
+    describe('and a param is missing', function () {
+      it('throws an Error', function () {
+        expect(function () {
+          formatPattern(pattern, {});
+        }).toThrow(Error);
+      });
+    });
+
+    describe('and a param is optional', function () {
+      var pattern = 'comments/(:id)/edit';
+
+      it('returns the correct path when param is supplied', function () {
+        expect(formatPattern(pattern, { id:'123' })).toEqual('comments/123/edit');
+      });
+
+      it('returns the correct path when param is not supplied', function () {
+        expect(formatPattern(pattern, {})).toEqual('comments/edit');
+      });
+    });
+
+    describe('and a param and forward slash are optional', function () {
+      var pattern = 'comments(/:id)/edit';
+
+      it('returns the correct path when param is supplied', function () {
+        expect(formatPattern(pattern, { id:'123' })).toEqual('comments/123/edit');
+      });
+
+      it('returns the correct path when param is not supplied', function () {
+        expect(formatPattern(pattern, {})).toEqual('comments/edit');
+      });
+    });
+
+    describe('and all params are present', function () {
+      it('returns the correct path', function () {
+        expect(formatPattern(pattern, { id: 'abc' })).toEqual('comments/abc/edit');
+      });
+
+      it('returns the correct path when the value is 0', function () {
+        expect(formatPattern(pattern, { id: 0 })).toEqual('comments/0/edit');
+      });
+    });
+
+    describe('and some params have special URL encoding', function () {
+      it('returns the correct path', function () {
+        expect(formatPattern(pattern, { id: 'one, two' })).toEqual('comments/one, two/edit');
+      });
+    });
+
+    describe('and a param has a forward slash', function () {
+      it('preserves the forward slash', function () {
+        expect(formatPattern(pattern, { id: 'the/id' })).toEqual('comments/the/id/edit');
+      });
+    });
+
+    describe('and some params contain dots', function () {
+      it('returns the correct path', function () {
+        expect(formatPattern(pattern, { id: 'alt.black.helicopter' })).toEqual('comments/alt.black.helicopter/edit');
+      });
+    });
+  });
+
+  describe('when a pattern has one splat', function () {
+    it('returns the correct path', function () {
+      expect(formatPattern('/a/*/d', { splat: 'b/c' })).toEqual('/a/b/c/d');
+    });
+  });
+
+  describe('when a pattern has multiple splats', function () {
+    it('returns the correct path', function () {
+      expect(formatPattern('/a/*/c/*', { splat: [ 'b', 'd' ] })).toEqual('/a/b/c/d');
+    });
+
+    it('complains if not given enough splat values', function () {
+      expect(function () {
+        formatPattern('/a/*/c/*', { splat: [ 'b' ] });
+      }).toThrow(Error);
+    });
+  });
+
+  describe('when a pattern has dots', function () {
+    it('returns the correct path', function () {
+      expect(formatPattern('/foo.bar.baz')).toEqual('/foo.bar.baz');
+    });
+  });
+});