Add support for passing severities

Previously, messages could be either turned on (as warnings), or
turned off.  This update adds support for setting these through an
integer (`1` and `0` respectivly), in array form:

```js
remark().use(lint, {finalNewline:[0]});
```

Additionally, the integer `2` can be passed to turn a message into
a fatal error:

```js
remark().use(lint, {maximumLineLength: [2, 72]});
```

Closes GH-65.

doc/rules.md

@@ -6,7 +6,7 @@ This document describes all (57)
 available rules, what they check for, examples of
 what they warn for, and how to fix their warnings.
 
-Note: both camel-cased and dash-cases versions of rule id’s
+Both camel-cased and dash-cases versions of rule id’s
 are supported in configuration objects:
 
 ```json
@@ -23,6 +23,33 @@ are supported in configuration objects:
 }
 ```
 
+Additionally, each rule can be configured with a severity
+instead of a boolean as well.  The following is handled the
+same as passing `false`:
+
+```json
+{
+  "final-newline": [0]
+}
+```
+
+...and passing `[1]` is as passing `true`.  To trigger an
+error instead of a warning, pass `2`:
+
+```json
+{
+  "final-newline": [2]
+}
+```
+
+It’s also possible to pass both a severity and configuration:
+
+```json
+{
+  "maximum-line-length": [2, 70]
+}
+```
+
 ## Table of Contents
 
 -   [reset](#reset)

lib/index.js

@@ -51,30 +51,17 @@ function lint(remark, options) {
   var disable = [];
   var known = [];
   var pipeline = trough();
-  var setting;
+  var config;
   var id;
 
   /* Add each rule. */
   for (id in rules) {
-    setting = settings[id];
-
     known.push(id);
+    config = coerce(id, settings[id], reset);
 
-    if (setting != null) {
-      /* Pass turned on rules `undefined`. */
-      if (reset && setting === true) {
-        setting = undefined;
-      }
+    (config[0] ? enable : disable).push(id);
 
-      if (setting === false) {
-        setting = undefined;
-        disable.push(id);
-      } else {
-        enable.push(id);
-      }
-    }
-
-    pipeline.use(ruleFactory(id, rules[id], setting));
+    pipeline.use(ruleFactory(id, rules[id], config[0], config[1]));
   }
 
   /* Run all rules. */
@@ -155,11 +142,13 @@ function loadExternals(externals) {
  *
  * @param {string} id - Identifier.
  * @param {Function} rule - Rule
+ * @param {number} severity - Severity.
  * @param {*} options - Options for respective rule.
  * @return {Function} - Trough ware.
  */
-function ruleFactory(id, rule, options) {
+function ruleFactory(id, rule, severity, options) {
   var fn = wrapped(rule);
+  var fatal = severity === 2;
 
   return function (ast, file, next) {
     var scope = file.namespace('remark-lint');
@@ -169,10 +158,13 @@ function ruleFactory(id, rule, options) {
 
     fn(ast, file, options, function (err) {
       var messages = file.messages;
+      var message;
 
       while (scope.index < messages.length) {
-        messages[scope.index].ruleId = id;
-        messages[scope.index].source = SOURCE;
+        message = messages[scope.index];
+        message.ruleId = id;
+        message.source = SOURCE;
+        message.fatal = fatal;
 
         scope.index++;
       }
@@ -182,13 +174,7 @@ function ruleFactory(id, rule, options) {
   };
 }
 
-/**
- * Helper to ensure ruleId’s are dash-cased instead of
- * camel-cased.
- *
- * @param {Object} source - Original settings.
- * @return {Object} - Dash-cased settings.
- */
+/* Ensure ruleId’s are dash-cased. */
 function decamelizeSettings(source) {
   var result = {};
   var key;
@@ -199,3 +185,35 @@ function decamelizeSettings(source) {
 
   return result;
 }
+
+/* Coerce a value to a severity--options tuple. */
+function coerce(name, value, reset) {
+  var def = reset ? 0 : 1;
+  var result;
+
+  if (value == null) {
+    result = [def];
+  } else if (typeof value === 'boolean') {
+    result = [value];
+  } else if (
+    typeof value === 'object' &&
+    (typeof value[0] === 'number' || typeof value[0] === 'boolean')
+  ) {
+    result = value.concat();
+  } else {
+    result = [1, value];
+  }
+
+  if (typeof result[0] === 'boolean') {
+    result[0] = result[0] ? 1 : 0;
+  }
+
+  if (result[0] < 0 || result[0] > 2) {
+    throw new Error(
+      'Invalid severity `' + result[0] + '` for `' + name + '`, ' +
+      'expected 0, 1, or 2'
+    );
+  }
+
+  return result;
+}

script/build-docs.js

@@ -104,7 +104,7 @@ var markdown = remark().use(toc);
       'available rules, what they check for, examples of',
       'what they warn for, and how to fix their warnings.',
       '',
-      'Note: both camel-cased and dash-cases versions of rule id’s',
+      'Both camel-cased and dash-cases versions of rule id’s',
       'are supported in configuration objects:',
       '',
       '```json',
@@ -121,6 +121,33 @@ var markdown = remark().use(toc);
       '}',
       '```',
       '',
+      'Additionally, each rule can be configured with a severity',
+      'instead of a boolean as well.  The following is handled the',
+      'same as passing `false`:',
+      '',
+      '```json',
+      '{',
+      '  "final-newline": [0]',
+      '}',
+      '```',
+      '',
+      '...and passing `[1]` is as passing `true`.  To trigger an',
+      'error instead of a warning, pass `2`:',
+      '',
+      '```json',
+      '{',
+      '  "final-newline": [2]',
+      '}',
+      '```',
+      '',
+      'It’s also possible to pass both a severity and configuration:',
+      '',
+      '```json',
+      '{',
+      '  "maximum-line-length": [2, 70]',
+      '}',
+      '```',
+      '',
       '## Table of Contents',
       '',
       '## `reset`',

test/index.js

@@ -85,6 +85,42 @@ test('core', function (t) {
       });
   });
 
+  t.test('should support a list with a severity', function (st) {
+    st.plan(3);
+
+    remark()
+      .use(lint, {reset: true, finalNewline: [2]})
+      .process('.', function (err, file) {
+        st.ifErr(err, 'should not fail');
+        st.equal(
+          file.messages.join(),
+          '1:1: Missing newline character at end of file',
+          'should trigger fatally (1)'
+        );
+        st.equal(file.messages[0].fatal, true, 'should trigger fatally (2)');
+      });
+  });
+
+  t.test('should fail on invalid severities', function (st) {
+    st.throws(
+      function () {
+        remark().use(lint, {finalNewline: [3]});
+      },
+      /^Error: Invalid severity `3` for `final-newline`, expected 0, 1, or 2$/,
+      'should throw when too high'
+    );
+
+    st.throws(
+      function () {
+        remark().use(lint, {finalNewline: [-1]});
+      },
+      /^Error: Invalid severity `-1` for `final-newline`, expected 0, 1, or 2$/,
+      'should throw too low'
+    );
+
+    st.end();
+  });
+
   t.end();
 });