[[FEAT]] Introduce linting option leanswitch

jshint · Dec 23, 2018 · 1f008f2 · 1f008f2
1 parent 06f54d0
commit 1f008f2
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Showing 5 changed files with 117 additions and 2 deletions.
diff --git a/src/jshint.js b/src/jshint.js
@@ -4266,6 +4266,12 @@ var JSHINT = (function() {
         case "return":
         case "switch":
         case "throw":
+          break;
+        case "default":
+          if (state.option.leanswitch) {
+            warning("W145", state.tokens.next);
+          }
+
           break;
         default:
           // You can tell JSHint that you don't use break intentionally by
@@ -4290,6 +4296,12 @@ var JSHINT = (function() {
         case "continue":
         case "return":
         case "throw":
+          break;
+        case "case":
+          if (state.option.leanswitch) {
+            warning("W145", state.tokens.curr);
+          }
+
           break;
         default:
           // Do not display a warning if 'default' is the first statement or if
@@ -4304,6 +4316,7 @@ var JSHINT = (function() {
         advance("default");
         g = true;
         advance(":");
+        state.funct["(verb)"] = "default";
         break;
       case "}":
         if (!noindent)

diff --git a/src/messages.js b/src/messages.js
@@ -235,7 +235,8 @@ var warnings = {
   W142: "Empty {a}: consider replacing with `import '{b}';`.",
   W143: "Assignment to properties of a mapped arguments object may cause " +
     "unexpected changes to formal parameters.",
-  W144: "'{a}' is a non-standard language feature. Enable it using the '{b}' unstable option."
+  W144: "'{a}' is a non-standard language feature. Enable it using the '{b}' unstable option.",
+  W145: "Superfluous 'case' clause."
 };
 
 var info = {

diff --git a/src/options.js b/src/options.js
@@ -122,6 +122,21 @@ exports.bool = {
      */
     immed       : true,
 
+    /**
+     * This option prohibits unnecessary clauses within `switch` statements,
+     * e.g.
+     *
+     *     switch (x) {
+     *       case 1:
+     *       default:
+     *         z();
+     *     }
+     *
+     * While clauses like these are techincally valid, they do not effect
+     * program behavior and may indicate an erroneous refactoring.
+     */
+    leanswitch  : true,
+
     /**
      * This option requires you to capitalize names of constructor functions.
      * Capitalizing functions that are intended to be used with `new` operator

diff --git a/tests/unit/core.js b/tests/unit/core.js
@@ -270,7 +270,6 @@ exports.switchFallThrough = function (test) {
   var src = fs.readFileSync(__dirname + '/fixtures/switchFallThrough.js', 'utf8');
   TestRun(test)
     .addError(3, 18, "Expected a 'break' statement before 'case'.")
-    .addError(18, 7, "Expected a 'break' statement before 'default'.")
     .addError(40, 12, "Unexpected ':'.")
     .test(src);
 

diff --git a/tests/unit/options.js b/tests/unit/options.js
@@ -4264,3 +4264,90 @@ exports.unstable = function (test) {
 
   test.done();
 };
+
+exports.leanswitch = function (test) {
+  var code = [
+      "switch (0) {",
+      "  case 0:",
+      "  default:",
+      "    break;",
+      "}"
+    ];
+  TestRun(test, "empty case clause followed by default")
+    .test(code);
+  TestRun(test, "empty case clause followed by default")
+    .addError(2, 9, "Superfluous 'case' clause.")
+    .test(code, { leanswitch: true });
+
+  code = [
+      "switch (0) {",
+      "  case 0:",
+      "  case 1:",
+      "    break;",
+      "}"
+    ];
+  TestRun(test, "empty case clause followed by case")
+    .test(code);
+  TestRun(test, "empty case clause followed by case")
+    .test(code, { leanswitch: true });
+
+  code = [
+      "switch (0) {",
+      "  default:",
+      "  case 0:",
+      "    break;",
+      "}"
+    ];
+  TestRun(test, "empty default clause followed by case")
+    .test(code);
+  TestRun(test, "empty default clause followed by case")
+    .addError(3, 3, "Superfluous 'case' clause.")
+    .test(code, { leanswitch: true });
+
+  code = [
+      "switch (0) {",
+      "  case 0:",
+      "    void 0;",
+      "  default:",
+      "    break;",
+      "}"
+    ];
+  TestRun(test, "non-empty case clause followed by default")
+    .addError(3, 11, "Expected a 'break' statement before 'default'.")
+    .test(code);
+  TestRun(test, "non-empty case clause followed by default")
+    .addError(3, 11, "Expected a 'break' statement before 'default'.")
+    .test(code, { leanswitch: true });
+
+  code = [
+      "switch (0) {",
+      "  case 0:",
+      "    void 0;",
+      "  case 1:",
+      "    break;",
+      "}"
+    ];
+  TestRun(test, "non-empty case clause followed by case")
+    .addError(3, 11, "Expected a 'break' statement before 'case'.")
+    .test(code);
+  TestRun(test, "non-empty case clause followed by case")
+    .addError(3, 11, "Expected a 'break' statement before 'case'.")
+    .test(code, { leanswitch: true });
+
+  code = [
+      "switch (0) {",
+      "  default:",
+      "    void 0;",
+      "  case 0:",
+      "    break;",
+      "}"
+    ];
+  TestRun(test, "non-empty default clause followed by case")
+    .addError(3, 11, "Expected a 'break' statement before 'case'.")
+    .test(code);
+  TestRun(test, "non-empty default clause followed by case")
+    .addError(3, 11, "Expected a 'break' statement before 'case'.")
+    .test(code, { leanswitch: true });
+
+  test.done();
+};