Allow category deep nesting

logtape/category.ts

@@ -0,0 +1,14 @@
+export type CategoryList = readonly string[];
+
+export type Category = string | readonly Category[];
+
+export function getCategoryList(category: Category): CategoryList {
+  return deepFlatten(category);
+}
+
+function deepFlatten(arr: Category): string[] {
+  if (typeof arr === "string") return [arr];
+  return arr.flatMap((item) => (
+    typeof item === "string" ? [item] : deepFlatten(item)
+  ));
+}

logtape/config.ts

@@ -1,3 +1,4 @@
+import type { Category } from "./category.ts";
 import { type FilterLike, toFilter } from "./filter.ts";
 import type { LogLevel } from "./level.ts";
 import { LoggerImpl } from "./logger.ts";
@@ -40,7 +41,7 @@ export interface LoggerConfig<
    * The category of the logger.  If a string, it is equivalent to an array
    * with one element.
    */
-  category: string | string[];
+  category: Category;
 
   /**
    * The sink identifiers to use.

logtape/formatter.ts

@@ -1,3 +1,4 @@
+import type { CategoryList } from "./category.ts";
 import type { LogLevel } from "./level.ts";
 import util from "./nodeUtil.ts";
 import type { LogRecord } from "./record.ts";
@@ -154,7 +155,7 @@ export interface TextFormatterOptions {
    * If this is a function, it will be called with the category array and
    * should return a string, which will be used for rendering the category.
    */
-  category?: string | ((category: readonly string[]) => string);
+  category?: string | ((category: CategoryList) => string);
 
   /**
    * The format of the embedded values.

logtape/logger.test.ts

@@ -37,6 +37,10 @@ Deno.test("getLogger()", () => {
     getLogger(["foo", "bar"]),
     getLogger().getChild("foo").getChild("bar"),
   );
+  assertStrictEquals(
+    getLogger(["foo", ["bar", ["baz", ["qux"]]]]),
+    getLogger().getChild("foo").getChild("bar").getChild("baz").getChild("qux"),
+  );
 });
 
 Deno.test("Logger.getChild()", () => {

logtape/logger.ts

@@ -1,3 +1,8 @@
+import {
+  type Category,
+  type CategoryList,
+  getCategoryList,
+} from "./category.ts";
 import type { Filter } from "./filter.ts";
 import type { LogLevel } from "./level.ts";
 import type { LogRecord } from "./record.ts";
@@ -20,7 +25,7 @@ export interface Logger {
   /**
    * The category of the logger.  It is an array of strings.
    */
-  readonly category: readonly string[];
+  readonly category: CategoryList;
 
   /**
    * The logger with the supercategory of the current logger.  If the current
@@ -46,9 +51,7 @@ export interface Logger {
    * @param subcategory The subcategory.
    * @returns The child logger.
    */
-  getChild(
-    subcategory: string | readonly [string] | readonly [string, ...string[]],
-  ): Logger;
+  getChild(subcategory: Category): Logger;
 
   /**
    * Get a logger with contextual properties.  This is useful for
@@ -385,7 +388,7 @@ export type LogTemplatePrefix = (
  *                 with a single element.
  * @returns The logger.
  */
-export function getLogger(category: string | readonly string[] = []): Logger {
+export function getLogger(category: Category = []): Logger {
   return LoggerImpl.getLogger(category);
 }
 
@@ -408,12 +411,12 @@ interface GlobalRootLoggerRegistry {
 export class LoggerImpl implements Logger {
   readonly parent: LoggerImpl | null;
   readonly children: Record<string, LoggerImpl | WeakRef<LoggerImpl>>;
-  readonly category: readonly string[];
+  readonly category: CategoryList;
   readonly sinks: Sink[];
   parentSinks: "inherit" | "override" = "inherit";
   readonly filters: Filter[];
 
-  static getLogger(category: string | readonly string[] = []): LoggerImpl {
+  static getLogger(category: Category = []): LoggerImpl {
     let rootLogger: LoggerImpl | null = globalRootLoggerSymbol in globalThis
       ? ((globalThis as GlobalRootLoggerRegistry)[globalRootLoggerSymbol] ??
         null)
@@ -423,12 +426,11 @@ export class LoggerImpl implements Logger {
       (globalThis as GlobalRootLoggerRegistry)[globalRootLoggerSymbol] =
         rootLogger;
     }
-    if (typeof category === "string") return rootLogger.getChild(category);
     if (category.length === 0) return rootLogger;
-    return rootLogger.getChild(category as readonly [string, ...string[]]);
+    return rootLogger.getChild(category);
   }
 
-  private constructor(parent: LoggerImpl | null, category: readonly string[]) {
+  constructor(parent: LoggerImpl | null, category: CategoryList) {
     this.parent = parent;
     this.children = {};
     this.category = category;
@@ -437,12 +439,10 @@ export class LoggerImpl implements Logger {
   }
 
   getChild(
-    subcategory:
-      | string
-      | readonly [string]
-      | readonly [string, ...(readonly string[])],
+    subcategory: Category,
   ): LoggerImpl {
-    const name = typeof subcategory === "string" ? subcategory : subcategory[0];
+    const subcategoryList = getCategoryList(subcategory);
+    const name = subcategoryList[0];
     const childRef = this.children[name];
     let child: LoggerImpl | undefined = childRef instanceof LoggerImpl
       ? childRef
@@ -453,12 +453,10 @@ export class LoggerImpl implements Logger {
         ? new WeakRef(child)
         : child;
     }
-    if (typeof subcategory === "string" || subcategory.length === 1) {
+    if (subcategoryList.length === 1) {
       return child;
     }
-    return child.getChild(
-      subcategory.slice(1) as [string, ...(readonly string[])],
-    );
+    return child.getChild(subcategoryList.slice(1));
   }
 
   /**
@@ -683,7 +681,7 @@ export class LoggerCtx implements Logger {
     this.properties = properties;
   }
 
-  get category(): readonly string[] {
+  get category(): CategoryList {
     return this.logger.category;
   }
 
@@ -692,7 +690,7 @@ export class LoggerCtx implements Logger {
   }
 
   getChild(
-    subcategory: string | readonly [string] | readonly [string, ...string[]],
+    subcategory: Category,
   ): Logger {
     return this.logger.getChild(subcategory).with(this.properties);
   }

logtape/mod.ts

@@ -1,3 +1,4 @@
+export { type Category, type CategoryList } from "./category.ts";
 export {
   type Config,
   ConfigError,

logtape/record.ts

@@ -1,3 +1,4 @@
+import type { CategoryList } from "./category.ts";
 import type { LogLevel } from "./level.ts";
 
 /**
@@ -7,7 +8,7 @@ export interface LogRecord {
   /**
    * The category of the logger that produced the log record.
    */
-  readonly category: readonly string[];
+  readonly category: CategoryList;
 
   /**
    * The log level.