Add Logger IoC context entry (#7)

package.json

@@ -24,6 +24,7 @@
   "exports": "./dist/logger.js",
   "devDependencies": {
     "@jest/globals": "^27.0.6",
+    "@proc7ts/context-builder": "^7.0.1",
     "@rollup/plugin-node-resolve": "^13.0.2",
     "@run-z/eslint-config": "^1.3.0",
     "@run-z/rollup-helpers": "^1.1.1",
@@ -60,5 +61,8 @@
     "lint:md": "run-z +z --then remark .",
     "test": "run-z +z env:NODE_OPTIONS='--experimental-vm-modules --no-warnings' --then jest",
     "z": "run-z +cmd:rollup,+cmd:typedoc,+cmd:eslint,+cmd:remark,+cmd:jest"
+  },
+  "dependencies": {
+    "@proc7ts/context-values": "^7.0.0"
   }
 }

src/logger.spec.ts

@@ -0,0 +1,72 @@
+import { afterEach, beforeEach, describe, expect, it, jest } from '@jest/globals';
+import { CxBuilder, cxConstAsset } from '@proc7ts/context-builder';
+import { CxGlobals } from '@proc7ts/context-values';
+import { SpyInstance, spyOn } from 'jest-mock';
+import { Logger } from './logger';
+import { consoleLogger } from './loggers';
+
+describe('Logger', () => {
+
+  let cxBuilder: CxBuilder;
+
+  beforeEach(() => {
+    cxBuilder = new CxBuilder(get => ({ get }));
+    cxBuilder.provide(cxConstAsset(CxGlobals, cxBuilder.context));
+  });
+
+  let logger: Logger;
+
+  beforeEach(() => {
+    logger = cxBuilder.get(Logger);
+  });
+
+  it('logs to most recent logger', () => {
+
+    const testLogger = {
+      error: jest.fn<void, unknown[]>(),
+    } as Partial<Logger> as Logger;
+
+    cxBuilder.provide(cxConstAsset(Logger, testLogger));
+
+    const error = new Error('Test');
+
+    logger.error('Error', error);
+
+    expect(testLogger.error).toHaveBeenCalledWith('Error', error);
+    expect(testLogger.error).toHaveBeenCalledTimes(1);
+  });
+  it('is singleton', () => {
+
+    const cxBuilder2 = new CxBuilder(get => ({ get }), cxBuilder);
+
+    expect(cxBuilder2.get(Logger)).toBe(logger);
+  });
+
+  describe('by default', () => {
+
+    let errorSpy: SpyInstance<void, unknown[]>;
+
+    beforeEach(() => {
+      errorSpy = spyOn(consoleLogger, 'error').mockImplementation(() => void 0);
+    });
+    afterEach(() => {
+      errorSpy.mockRestore();
+    });
+
+    it('logs to console', () => {
+
+      const error = new Error('Test');
+
+      logger.error('Error', error);
+
+      expect(errorSpy).toHaveBeenCalledWith('Error', error);
+      expect(errorSpy).toHaveBeenCalledTimes(1);
+    });
+  });
+
+  describe('toString', () => {
+    it('provides string representation', () => {
+      expect(String(Logger)).toBe('[Logger]');
+    });
+  });
+});

src/logger.ts

@@ -1,3 +1,6 @@
+import { CxEntry, CxGlobals, cxRecent, cxScoped } from '@proc7ts/context-values';
+import { consoleLogger, proxyLogger } from './loggers';
+
 /**
  * Basic logger interface.
  */
@@ -41,3 +44,25 @@ export interface Logger {
   trace(...args: unknown[]): void;
 
 }
+
+/**
+ * Global context entry containing logger to use.
+ *
+ * Logs to {@link consoleLogger console} by default.
+ */
+export const Logger: CxEntry<Logger> = {
+  perContext: (/*#__PURE__*/ cxScoped(
+      CxGlobals,
+      (/*#__PURE__*/ cxRecent({
+        create: (recent, _) => recent,
+        byDefault: _ => consoleLogger,
+        assign({ get, to }) {
+
+          const logger = proxyLogger(get);
+
+          return receiver => to((_, by) => receiver(logger, by));
+        },
+      })),
+  )),
+  toString: () => '[Logger]',
+};