Improve logging API

Adds multiple variable support and the ability to set statement level logging semantics.

This breaks that logger API, cleaning up the manner in which enums are set, but the other behaviors are backwards compatible.

Fixes #956

Author: kpdecker

Diff for: lib/handlebars/helpers/log.js

@@ -1,6 +1,19 @@
 export default function(instance) {
-  instance.registerHelper('log', function(message, options) {
-    let level = options.data && options.data.level != null ? parseInt(options.data.level, 10) : 1;
-    instance.log(level, message);
+  instance.registerHelper('log', function(/* message, options */) {
+    let args = [undefined],
+        options = arguments[arguments.length - 1];
+    for (let i = 0; i < arguments.length - 1; i++) {
+      args.push(arguments[i]);
+    }
+
+    let level = 1;
+    if (options.hash.level != null) {
+      level = options.hash.level;
+    } else if (options.data && options.data.level != null) {
+      level = options.data.level;
+    }
+    args[0] = level;
+
+    instance.log(... args);
   });
 }

Diff for: lib/handlebars/logger.js

@@ -1,18 +1,31 @@
 let logger = {
-  methodMap: { 0: 'debug', 1: 'info', 2: 'warn', 3: 'error' },
+  methodMap: ['debug', 'info', 'warn', 'error'],
+  level: 'info',
 
-  // State enum
-  DEBUG: 0,
-  INFO: 1,
-  WARN: 2,
-  ERROR: 3,
-  level: 1,
+  // Maps a given level value to the `methodMap` indexes above.
+  lookupLevel: function(level) {
+    if (typeof level === 'string') {
+      let levelMap = logger.methodMap.indexOf(level.toLowerCase());
+      if (levelMap >= 0) {
+        level = levelMap;
+      } else {
+        level = parseInt(level, 10);
+      }
+    }
+
+    return level;
+  },
 
   // Can be overridden in the host environment
-  log: function(level, message) {
-    if (typeof console !== 'undefined' && logger.level <= level) {
+  log: function(level, ...message) {
+    level = logger.lookupLevel(level);
+
+    if (typeof console !== 'undefined' && logger.lookupLevel(logger.level) <= level) {
       let method = logger.methodMap[level];
-      (console[method] || console.log).call(console, message);    // eslint-disable-line no-console
+      if (!console[method]) {   // eslint-disable-line no-console
+        method = 'log';
+      }
+      console[method](...message);    // eslint-disable-line no-console
     }
   }
 };

Diff for: spec/builtins.js

@@ -286,7 +286,7 @@ describe('builtin helpers', function() {
       };
 
       shouldCompileTo(string, [hash,,,, {level: '03'}], '');
-      equals(3, levelArg);
+      equals('03', levelArg);
       equals('whee', logArg);
     });
     it('should output to info', function() {
@@ -327,6 +327,66 @@ describe('builtin helpers', function() {
 
       shouldCompileTo(string, [hash,,,, {level: '03'}], '');
     });
+
+    it('should handle string log levels', function() {
+      var string = '{{log blah}}';
+      var hash = { blah: 'whee' };
+      var called;
+
+      console.error = function(log) {
+        equals('whee', log);
+        called = true;
+      };
+
+      shouldCompileTo(string, [hash,,,, {level: 'error'}], '');
+      equals(true, called);
+
+      called = false;
+
+      shouldCompileTo(string, [hash,,,, {level: 'ERROR'}], '');
+      equals(true, called);
+    });
+    it('should handle hash log levels', function() {
+      var string = '{{log blah level="error"}}';
+      var hash = { blah: 'whee' };
+      var called;
+
+      console.error = function(log) {
+        equals('whee', log);
+        called = true;
+      };
+
+      shouldCompileTo(string, hash, '');
+      equals(true, called);
+    });
+    it('should handle hash log levels', function() {
+      var string = '{{log blah level="debug"}}';
+      var hash = { blah: 'whee' };
+      var called = false;
+
+      console.info = console.log = console.error = console.debug = function(log) {
+        equals('whee', log);
+        called = true;
+      };
+
+      shouldCompileTo(string, hash, '');
+      equals(false, called);
+    });
+    it('should pass multiple log arguments', function() {
+      var string = '{{log blah "foo" 1}}';
+      var hash = { blah: 'whee' };
+      var called;
+
+      console.info = console.log = function(log1, log2, log3) {
+        equals('whee', log1);
+        equals('foo', log2);
+        equals(1, log3);
+        called = true;
+      };
+
+      shouldCompileTo(string, hash, '');
+      equals(true, called);
+    });
     /*eslint-enable no-console */
   });