feat: add appenders and level inheritance

lib/categories.js

@@ -21,23 +21,39 @@ function inheritFromParent(config, category, categoryName) {
   if (lastDotIndex < 0) return; // category is not a child
   const parentCategoryName = categoryName.substring(0, lastDotIndex);
   let parentCategory = config.categories[parentCategoryName];
+
+
   if (!parentCategory) {
-    parentCategory = { inherit: true };
-    config.categories[parentCategoryName] = parentCategory;
-  }
-  // make sure parent has had its inheritance taken care of before pulling its properties to this child
-  inheritFromParent(config, parentCategory, parentCategoryName);
-
-  category.appenders = category.appenders || [];
-  category.level = category.level || parentCategory.level;
-
-  // merge in appenders from parent (parent is already holding its inherited appenders)
-  parentCategory.appenders.forEach((ap) => {
-    if (!category.appenders.includes(ap)) {
-      category.appenders.push(ap);
+    // parent is missing, may need to implicitly create it, so that it can inherit from its parents
+    if (parentCategoryName.lastIndexOf('.') >= 0) { // don't create a missing root category, it can inherit nothing
+      parentCategory = { inherit: true, appenders: [] };
     }
-  });
-  category.parent = parentCategory;
+  }
+
+  if (parentCategory) {
+    // make sure parent has had its inheritance taken care of before pulling its properties to this child
+    inheritFromParent(config, parentCategory, parentCategoryName);
+
+    // if the parent is not in the config (because we just created it above),
+    // and it inherited a valid configuration, add it to config.categories
+    if (!config.categories[parentCategoryName]
+      && parentCategory.appenders
+      && parentCategory.appenders.length
+      && parentCategory.level) {
+      config.categories[parentCategoryName] = parentCategory;
+    }
+
+    category.appenders = category.appenders || [];
+    category.level = category.level || parentCategory.level;
+
+    // merge in appenders from parent (parent is already holding its inherited appenders)
+    parentCategory.appenders.forEach((ap) => {
+      if (!category.appenders.includes(ap)) {
+        category.appenders.push(ap);
+      }
+    });
+    category.parent = parentCategory;
+  }
 }
 
 
@@ -106,7 +122,7 @@ configuration.addListener((config) => {
       config,
       configuration.not(levels.getLevel(category.level)),
       `category "${name}" is not valid (level "${category.level}" not recognised;`
-        + ` valid levels are ${levels.levels.join(', ')})`
+      + ` valid levels are ${levels.levels.join(', ')})`
     );
   });
 
@@ -161,7 +177,7 @@ const setLevelForCategory = (category, level) => {
   if (!categoryConfig) {
     const sourceCategoryConfig = configForCategory(category);
     debug('setLevelForCategory: no config found for category, '
-        + `found ${sourceCategoryConfig} for parents of ${category}`);
+      + `found ${sourceCategoryConfig} for parents of ${category}`);
     categoryConfig = { appenders: sourceCategoryConfig.appenders };
   }
   categoryConfig.level = level;

test/tap/configuration-inheritance-test.js

@@ -132,6 +132,30 @@ test('log4js category inherit all appenders from direct parent', (batch) => {
     t.end();
   });
 
+  batch.test('should deal gracefully with missing parent', (t) => {
+    const config = {
+      appenders: {
+        stdout1: { type: 'stdout' },
+        stdout2: { type: 'stdout' }
+      },
+      categories: {
+        default: { appenders: ['stdout1'], level: 'ERROR' },
+        // no catA nor catA.catB, but should get created, with default values
+        'catA.catB.catC': { appenders: ['stdout2'], level: 'DEBUG' } // should get stdout2, DEBUG
+      }
+    };
+
+    log4js.configure(config);
+
+    const child = config.categories['catA.catB.catC'];
+    t.ok(child);
+    t.ok(child.appenders);
+    t.isEqual(child.appenders.length, 1);
+    t.ok(child.appenders.includes('stdout2'));
+
+    t.end();
+  });
+
 
   batch.test('should not get duplicate appenders if parent has the same one', (t) => {
     const config = {