unexpectedjs · alexjeffburke · Jan 5, 2020 · Jan 5, 2020 · Jan 9, 2020 · Jan 10, 2020
diff --git a/lib/assertions.js b/lib/assertions.js
@@ -302,8 +302,17 @@ module.exports = expect => {
 
   expect.addAssertion(
     '<object> to have [own] property <string> <any>',
-    (expect, subject, key, expectedPropertyValue) =>
-      expect(subject, 'to have [own] property', key).then(
+    (expect, subject, key, expectedPropertyValue) => {
+      if (expectedPropertyValue) {
+        utils.deprecationWarning(
+          "unexpected: The value argument of 'to have property' assertion is deprecated.\n" +
+            "Please use 'to have properties' with object argument instead:\n" +
+            'http://unexpected.js.org/assertions/object/to-have-properties/',
+          expect
+        );
+      }
+
+      return expect(subject, 'to have [own] property', key).then(
         actualPropertyValue => {
           expect.argsOutput = function() {
             this.appendInspected(key)
@@ -315,7 +324,8 @@ module.exports = expect => {
           expect(actualPropertyValue, 'to equal', expectedPropertyValue);
           return actualPropertyValue;
         }
-      )
+      );
+    }
   );
 
   expect.addAssertion(

diff --git a/lib/createTopLevelExpect.js b/lib/createTopLevelExpect.js
@@ -1633,7 +1633,9 @@ expectPrototype.freeze = function() {
 };
 
 expectPrototype.outputFormat = function(format) {
-  this._assertTopLevelExpect();
+  if (format) {
+    this._assertTopLevelExpect();
+  }
   if (typeof format === 'undefined') {
     return this._outputFormat;
   } else {

diff --git a/lib/styles.js b/lib/styles.js
@@ -93,6 +93,10 @@ module.exports = expect => {
     }
   });
 
+  expect.addStyle('deprecationWarning', function(value) {
+    this.text(value, 'bgYellow', 'black');
+  });
+
   expect.addStyle('singleQuotedString', function(content) {
     content = String(content);
     this.jsString("'")

diff --git a/lib/utils.js b/lib/utils.js
@@ -4,6 +4,7 @@
 const canSetPrototype =
   Object.setPrototypeOf || { __proto__: [] } instanceof Array;
 const greedyIntervalPacker = require('greedy-interval-packer');
+const magicpen = require('magicpen');
 
 const setPrototypeOf =
   Object.setPrototypeOf ||
@@ -375,5 +376,17 @@ const utils = (module.exports = {
     } else if (typeof process === 'object' && process.env) {
       return process.env[varName];
     }
+  },
+
+  deprecationWarning(message, expect) {
+    let format = expect.outputFormat();
+    if (format === 'html') {
+      // override given this will be output in the browser console
+      format = 'text';
+    }
+
+    console.warn(
+      expect.output.clone().deprecationWarning(message).toString(format)
+    );
   }
 });
diff --git a/test/api/outputFormat.spec.js b/test/api/outputFormat.spec.js
@@ -28,5 +28,22 @@ describe('outputFormat', () => {
         }
       );
     });
+
+    it('throws if being reset on a child expect', () => {
+      const clonedExpect = expect
+        .clone()
+        .addAssertion('<string> to foo', (expect, subject) => {
+          expect.child().outputFormat('html');
+          expect(subject, 'to contain', 'foo');
+        });
+
+      expect(
+        () => {
+          clonedExpect('foobar', 'to foo');
+        },
+        'to throw',
+        'This method only works on the top level expect function'
+      );
+    });
   });
 });