[[Fix]] Disallow ambiguous configuration values

In the presence of the recently-introduced `esversion` option, JSHint
should reject any occurrence of the equivalent legacy options: `es3`,
`es5`, and `esnext`.

Previous implementation conflated the user-specified option values and
the state of the linter itself. Without a formal distinction between
these two concepts, it was not possible to consistently enforce this
constraint. For example, the value of `state.option.esversion` could be
set to `5` directly (i.e. `esversion: 5`) or indirectly (i.e. `es5:
true`), but only in the former case would a later in-line configuration
of `esversion: 6` be acceptable.

Achieve this by making an explicit distinction between user-specified
option values (in other words, the `es3`, `es5`, `esnext`, and
`esversion` properties of the `state.option` object) and the state of
the linter itself (the new `state.esVersion` property).

src/jshint.js

@@ -187,19 +187,30 @@ var JSHINT = (function() {
   }
 
   function assume() {
+    var badESOpt = null;
     processenforceall();
 
     /**
      * TODO: Remove in JSHint 3
      */
-    if (!state.option.esversion && !state.option.moz) {
+    if (state.option.esversion) {
       if (state.option.es3) {
-        state.option.esversion = 3;
+        badESOpt = "es3";
+      } else if (state.option.es5) {
+        badESOpt = "es5";
       } else if (state.option.esnext) {
-        state.option.esversion = 6;
-      } else {
-        state.option.esversion = 5;
+        badESOpt = "esnext";
+      }
+
+      if (badESOpt) {
+        quit("E059", state.tokens.next, "esversion", badESOpt);
       }
+
+      state.esVersion = state.option.esversion;
+    } else if (state.option.es3) {
+      state.esVersion = 3;
+    } else if (state.option.esnext) {
+      state.esVersion = 6;
     }
 
     if (state.inES5()) {
@@ -675,31 +686,6 @@ var JSHINT = (function() {
           }
         }
 
-        /**
-         * TODO: Remove in JSHint 3
-         */
-        var esversions = {
-          es3   : 3,
-          es5   : 5,
-          esnext: 6
-        };
-        if (_.has(esversions, key)) {
-          switch (val) {
-          case "true":
-            state.option.moz = false;
-            state.option.esversion = esversions[key];
-            break;
-          case "false":
-            if (!state.option.moz) {
-              state.option.esversion = 5;
-            }
-            break;
-          default:
-            error("E002", nt);
-          }
-          return;
-        }
-
         if (key === "esversion") {
           switch (val) {
           case "5":

src/state.js

@@ -26,20 +26,20 @@ var state = {
    */
   inES6: function(strict) {
     if (strict) {
-      return this.option.esversion === 6;
+      return this.esVersion === 6;
     }
-    return this.option.moz || this.option.esversion >= 6;
+    return this.option.moz || this.esVersion >= 6;
   },
 
   /**
    * @param {boolean} strict - When `true`, return `true` only when
-   *                           esversion is exactly 5
+   *                           esVersion is exactly 5
    */
   inES5: function(strict) {
     if (strict) {
-      return (!this.option.esversion || this.option.esversion === 5) && !this.option.moz;
+      return (!this.esVersion || this.esVersion === 5) && !this.option.moz;
     }
-    return !this.option.esversion || this.option.esversion >= 5 || this.option.moz;
+    return !this.esVersion || this.esVersion >= 5 || this.option.moz;
   },
 
 
@@ -51,6 +51,7 @@ var state = {
     };
 
     this.option = {};
+    this.esVersion = 5;
     this.funct = null;
     this.ignored = {};
     this.directive = {};

tests/unit/options.js

@@ -3446,22 +3446,44 @@ exports.esversion = function(test) {
     .test(arrayComprehension, { esnext: true });
 
 
-  TestRun(test, "precedence over `es3`") // TODO: Remove in JSHint 3
+  TestRun(test, "incompatibility with `es3`") // TODO: Remove in JSHint 3
+    .addError(0, "Incompatible values for the 'esversion' and 'es3' linting options. (0% scanned).")
     .test(es6code, { esversion: 6, es3: true });
 
-  TestRun(test, "precedence over `es5`") // TODO: Remove in JSHint 3
+  TestRun(test, "incompatibility with `es5`") // TODO: Remove in JSHint 3
     .addError(0, "ES5 option is now set per default")
+    .addError(0, "Incompatible values for the 'esversion' and 'es5' linting options. (0% scanned).")
     .test(es6code, { esversion: 6, es5: true });
 
-  TestRun(test, "precedence over `esnext`") // TODO: Remove in JSHint 3
-    .addError(2, "'computed property names' is only available in ES6 (use 'esversion: 6').")
+  TestRun(test, "incompatibility with `esnext`") // TODO: Remove in JSHint 3
+    .addError(0, "Incompatible values for the 'esversion' and 'esnext' linting options. (0% scanned).")
     .test(es6code, { esversion: 3, esnext: true });
 
+  TestRun(test, "imcompatible option specified in-line")
+    .addError(2, "Incompatible values for the 'esversion' and 'es3' linting options. (66% scanned).")
+    .test(["", "// jshint esversion: 3", ""], { es3: true });
+
+  TestRun(test, "incompatible option specified in-line")
+    .addError(2, "Incompatible values for the 'esversion' and 'es3' linting options. (66% scanned).")
+    .test(["", "// jshint es3: true", ""], { esversion: 3 });
+
+  TestRun(test, "compatible option specified in-line")
+    .addError(3, "'class' is available in ES6 (use 'esversion: 6') or Mozilla JS extensions (use moz).")
+    .test(["", "// jshint esversion: 3", "class A {}"], { esversion: 3 });
+
+  TestRun(test, "compatible option specified in-line")
+    .addError(3, "'class' is available in ES6 (use 'esversion: 6') or Mozilla JS extensions (use moz).")
+    .test(["", "// jshint esversion: 3", "class A {}"], { esversion: 6 });
+
+  TestRun(test, "compatible option specified in-line")
+    .test(["", "// jshint esversion: 6", "class A {}"], { esversion: 3 });
+
   var code2 = [ // TODO: Remove in JSHint 3
     "/* jshint esversion: 3, esnext: true */"
   ].concat(es6code);
 
-  TestRun(test, "the last has the precedence (inline configuration)") // TODO: Remove in JSHint 3
+  TestRun(test, "incompatible options specified in-line") // TODO: Remove in JSHint 3
+    .addError(1, "Incompatible values for the 'esversion' and 'esnext' linting options. (25% scanned).")
     .test(code2);
 
   var code3 = [