Only build up data when needed.

Per #1250 (comment)

Author: ljharb

lib/rules/jsx-boolean-value.js

@@ -17,6 +17,16 @@ const exceptionsSchema = {
 const ALWAYS = 'always';
 const NEVER = 'never';
 
+const errorData = new WeakMap();
+function getErrorData(exceptions) {
+  if (!errorData.has(exceptions)) {
+    const exceptionProps = Array.from(exceptions, (name) => `\`${name}\``).join(', ');
+    const exceptionsMessage = exceptions.size > 0 ? ` for the following props: ${exceptionProps}` : '';
+    errorData.set(exceptions, {exceptionsMessage: exceptionsMessage});
+  }
+  return errorData.get(exceptions);
+}
+
 module.exports = {
   meta: {
     docs: {
@@ -63,9 +73,6 @@ module.exports = {
     const configuration = context.options[0] || NEVER;
     const configObject = context.options[1] || {};
     const exceptions = new Set((configuration === ALWAYS ? configObject[NEVER] : configObject[ALWAYS]) || []);
-    const exceptionProps = Array.from(exceptions, (name) => `\`${name}\``).join(', ');
-    const exceptionsMessage = exceptions.size > 0 ? ` for the following props: ${exceptionProps}` : '';
-    const data = {exceptionsMessage: exceptionsMessage};
 
     const NEVER_MESSAGE = 'Value must be omitted for boolean attributes{{exceptionsMessage}}';
     const ALWAYS_MESSAGE = 'Value must be set for boolean attributes{{exceptionsMessage}}';
@@ -80,6 +87,7 @@ module.exports = {
         const isNever = configuration === NEVER ? !isException : isException;
 
         if (isAlways && value === null) {
+          const data = getErrorData(exceptions);
           context.report({
             node: node,
             message: ALWAYS_MESSAGE,
@@ -90,6 +98,7 @@ module.exports = {
           });
         }
         if (isNever && value && value.type === 'JSXExpressionContainer' && value.expression.value === true) {
+          const data = getErrorData(exceptions);
           context.report({
             node: node,
             message: NEVER_MESSAGE,