Refactor isAlways/isNever logic

Per #1250 (comment)

Author: ljharb

lib/rules/jsx-boolean-value.js

@@ -27,6 +27,22 @@ function getErrorData(exceptions) {
   return errorData.get(exceptions);
 }
 
+function isAlways(configuration, exceptions, propName) {
+  const isException = exceptions.has(propName);
+  if (configuration === ALWAYS) {
+    return !isException;
+  }
+  return isException;
+}
+
+function isNever(configuration, exceptions, propName) {
+  const isException = exceptions.has(propName);
+  if (configuration === NEVER) {
+    return !isException;
+  }
+  return isException;
+}
+
 module.exports = {
   meta: {
     docs: {
@@ -69,7 +85,7 @@ module.exports = {
     }
   },
 
-  create: function(context) {
+  create(context) {
     const configuration = context.options[0] || NEVER;
     const configObject = context.options[1] || {};
     const exceptions = new Set((configuration === ALWAYS ? configObject[NEVER] : configObject[ALWAYS]) || []);
@@ -81,12 +97,8 @@ module.exports = {
       JSXAttribute(node) {
         const propName = node.name && node.name.name;
         const value = node.value;
-        const isException = exceptions.has(propName);
-
-        const isAlways = configuration === ALWAYS ? !isException : isException;
-        const isNever = configuration === NEVER ? !isException : isException;
 
-        if (isAlways && value === null) {
+        if (isAlways(configuration, exceptions, propName) && value === null) {
           const data = getErrorData(exceptions);
           context.report({
             node: node,
@@ -97,7 +109,7 @@ module.exports = {
             }
           });
         }
-        if (isNever && value && value.type === 'JSXExpressionContainer' && value.expression.value === true) {
+        if (isNever(configuration, exceptions, propName) && value && value.type === 'JSXExpressionContainer' && value.expression.value === true) {
           const data = getErrorData(exceptions);
           context.report({
             node: node,