feat(utils): add warn function

src/lib/__tests__/utils-test.js

@@ -876,7 +876,7 @@ describe('utils.deprecate', () => {
     const actual = 6;
 
     expect(actual).toBe(expectation);
-    expect(warn).toHaveBeenCalled();
+    expect(warn).toHaveBeenCalledWith('[InstantSearch.js]: message');
 
     warn.mockReset();
     warn.mockRestore();
@@ -899,6 +899,38 @@ describe('utils.deprecate', () => {
   });
 });
 
+describe('utils.warn', () => {
+  it('expect to print a warn message', () => {
+    const message = 'message';
+    const warn = jest.spyOn(global.console, 'warn');
+
+    utils.warn(message);
+
+    expect(warn).toHaveBeenCalledWith('[InstantSearch.js]: message');
+
+    warn.mockReset();
+    warn.mockRestore();
+    utils.warn.cache = {};
+  });
+
+  it('expect to print the same message only once', () => {
+    const message = 'message';
+    const warn = jest.spyOn(global.console, 'warn');
+
+    utils.warn(message);
+
+    expect(warn).toHaveBeenCalledTimes(1);
+
+    utils.warn(message);
+
+    expect(warn).toHaveBeenCalledTimes(1);
+
+    warn.mockReset();
+    warn.mockRestore();
+    utils.warn.cache = {};
+  });
+});
+
 describe('utils.parseAroundLatLngFromString', () => {
   it('expect to return a LatLng object from string', () => {
     const samples = [

src/lib/utils.js

@@ -25,6 +25,7 @@ export {
   checkRendering,
   isReactElement,
   deprecate,
+  warn,
   parseAroundLatLngFromString,
 };
 
@@ -401,21 +402,36 @@ function isReactElement(object) {
   );
 }
 
+function logger(message) {
+  // eslint-disable-next-line no-console
+  console.warn(`[InstantSearch.js]: ${message.trim()}`);
+}
+
 function deprecate(fn, message) {
   let hasAlreadyPrint = false;
 
   return function(...args) {
     if (!hasAlreadyPrint) {
       hasAlreadyPrint = true;
 
-      // eslint-disable-next-line no-console
-      console.warn(`[InstantSearch.js]: ${message}`);
+      logger(message);
     }
 
     return fn(...args);
   };
 }
 
+warn.cache = {};
+function warn(message) {
+  const hasAlreadyPrint = warn.cache[message];
+
+  if (!hasAlreadyPrint) {
+    warn.cache[message] = true;
+
+    logger(message);
+  }
+}
+
 const latLngRegExp = /^(-?\d+(?:\.\d+)?),\s*(-?\d+(?:\.\d+)?)$/;
 function parseAroundLatLngFromString(value) {
   const pattern = value.match(latLngRegExp);