Fix: Improve detection of static url strings in require-meta-docs-url rule

* Add static value detection for `url` variables
* Ignore when we can't statically determine the value of a given `url`
* Improve reporting location and tests for this
* Use `messageId`
* Add tests

Author: bmish

lib/rules/require-meta-docs-url.js

@@ -10,6 +10,7 @@
 
 const path = require('path');
 const util = require('../utils');
+const { getStaticValue } = require('eslint-utils');
 
 // -----------------------------------------------------------------------------
 // Rule Definition
@@ -31,6 +32,11 @@ module.exports = {
       },
       additionalProperties: false,
     }],
+    messages: {
+      mismatch: '`meta.docs.url` property must be `{{expectedUrl}}`.',
+      missing: 'Rules should export a `meta.docs.url` property.',
+      wrongType: '`meta.docs.url` property must be a string.',
+    },
   },
 
   /**
@@ -48,24 +54,22 @@ module.exports = {
       : options.pattern.replace(/{{\s*name\s*}}/g, ruleName);
 
     /**
-     * Check whether a given node is the expected URL.
-     * @param {Node} node The node of property value to check.
+     * Check whether a given URL is the expected URL.
+     * @param {String} url The URL to check.
      * @returns {boolean} `true` if the node is the expected URL.
      */
-    function isExpectedUrl (node) {
+    function isExpectedUrl (url) {
       return Boolean(
-        node &&
-        node.type === 'Literal' &&
-        typeof node.value === 'string' &&
+        typeof url === 'string' &&
         (
           expectedUrl === undefined ||
-          node.value === expectedUrl
+          url === expectedUrl
         )
       );
     }
 
     return {
-      Program (node) {
+      Program () {
         const info = util.getRuleInfo(sourceCode);
         if (info === null) {
           return;
@@ -81,40 +85,45 @@ module.exports = {
           docsPropNode.value.properties &&
           docsPropNode.value.properties.find(p => p.type === 'Property' && util.getKeyName(p) === 'url');
 
-        if (isExpectedUrl(urlPropNode && urlPropNode.value)) {
+        const staticValue = urlPropNode ? getStaticValue(urlPropNode.value, context.getScope()) : undefined;
+        if (urlPropNode && !staticValue) {
+          // Ignore non-static values since we can't determine what they look like.
+          return;
+        }
+
+        if (isExpectedUrl(staticValue && staticValue.value)) {
           return;
         }
 
         context.report({
-          loc:
-            (urlPropNode && urlPropNode.value.loc) ||
-            (docsPropNode && docsPropNode.value.loc) ||
-            (metaNode && metaNode.loc) ||
-            node.loc.start,
-
-          message:
-            !urlPropNode ? 'Rules should export a `meta.docs.url` property.' :
+          node: (urlPropNode && urlPropNode.value) || (docsPropNode && docsPropNode.value) || metaNode || info.create,
+
+          messageId:
+            !urlPropNode ? 'missing' :
               // eslint-disable-next-line unicorn/no-nested-ternary
-              !expectedUrl ? '`meta.docs.url` property must be a string.' :
-                /* otherwise */ '`meta.docs.url` property must be `{{expectedUrl}}`.',
+              !expectedUrl ? 'wrongType' :
+                /* otherwise */ 'mismatch',
 
           data: {
             expectedUrl,
           },
 
           fix (fixer) {
-            if (expectedUrl) {
-              const urlString = JSON.stringify(expectedUrl);
-              if (urlPropNode) {
+            if (!expectedUrl) {
+              return null;
+            }
+
+            const urlString = JSON.stringify(expectedUrl);
+            if (urlPropNode) {
+              if (urlPropNode.value.type === 'Literal' || (urlPropNode.value.type === 'Identifier' && urlPropNode.value.name === 'undefined')) {
                 return fixer.replaceText(urlPropNode.value, urlString);
               }
-              if (docsPropNode && docsPropNode.value.type === 'ObjectExpression') {
-                return util.insertProperty(fixer, docsPropNode.value, `url: ${urlString}`, sourceCode);
-              }
-              if (!docsPropNode && metaNode && metaNode.type === 'ObjectExpression') {
-                return util.insertProperty(fixer, metaNode, `docs: {\nurl: ${urlString}\n}`, sourceCode);
-              }
+            } else if (docsPropNode && docsPropNode.value.type === 'ObjectExpression') {
+              return util.insertProperty(fixer, docsPropNode.value, `url: ${urlString}`, sourceCode);
+            } else if (!docsPropNode && metaNode && metaNode.type === 'ObjectExpression') {
+              return util.insertProperty(fixer, metaNode, `docs: {\nurl: ${urlString}\n}`, sourceCode);
             }
+
             return null;
           },
         });