Merge pull request #1346 from Mumeii/feature/issue-1341

feat issue #1341 (Layouts) : support a specifier on %m

docs/layouts.md

@@ -134,6 +134,8 @@ Fields can be any of:
 - `%c` log category
 - `%h` hostname
 - `%m` log data
+- `%m{l}` where l is an integer, log data.slice(l)
+- `%m{l,u}` where l and u are integers, log data.slice(l, u)
 - `%d` date, formatted - default is `ISO8601`, format options are: `ISO8601`, `ISO8601_WITH_TZ_OFFSET`, `ABSOLUTETIME`, `DATETIME`, or any string compatible with the [date-format](https://www.npmjs.com/package/date-format) library. e.g. `%d{DATETIME}`, `%d{yyyy/MM/dd-hh.mm.ss}`
 - `%%` % - for when you want a literal `%` in your output
 - `%n` newline

lib/layouts.js

@@ -101,6 +101,8 @@ function dummyLayout(loggingEvent) {
  *  - %c log category
  *  - %h hostname
  *  - %m log data
+ *  - %m{l} where l is an integer, log data.slice(l)
+ *  - %m{l,u} where l and u are integers, log data.slice(l, u)
  *  - %d date in constious formats
  *  - %% %
  *  - %n newline
@@ -210,8 +212,13 @@ function patternLayout(pattern, tokens) {
     return os.hostname().toString();
   }
 
-  function formatMessage(loggingEvent) {
-    return util.format(...loggingEvent.data);
+  function formatMessage(loggingEvent, specifier) {
+    let dataSlice = loggingEvent.data;
+    if (specifier) {
+      const [lowerBound, upperBound] = specifier.split(',');
+      dataSlice = dataSlice.slice(lowerBound, upperBound);
+    }
+    return util.format(...dataSlice);
   }
 
   function endOfLine() {

test/tap/layouts-test.js

@@ -375,6 +375,101 @@ test('log4js layouts', (batch) => {
       assert.end();
     });
 
+    t.test('%m should apply util.format on data', (assert) => {
+      const eventWithSeveralDataEntry = JSON.parse(JSON.stringify(event));
+      eventWithSeveralDataEntry.data = [
+        'This %s a %s like other ones',
+        "isn't",
+        'test',
+      ];
+      testPattern(
+        assert,
+        layout,
+        eventWithSeveralDataEntry,
+        tokens,
+        '%m',
+        "This isn't a test like other ones"
+      );
+      assert.end();
+    });
+
+    t.test('%m{1} should only consider data.slice(1)', (assert) => {
+      const eventWithSeveralDataEntry = JSON.parse(JSON.stringify(event));
+      eventWithSeveralDataEntry.data = [
+        'This %s a %s like other ones',
+        "isn't",
+        'test',
+      ];
+      testPattern(
+        assert,
+        layout,
+        eventWithSeveralDataEntry,
+        tokens,
+        '%m{1}',
+        "isn't test"
+      );
+      assert.end();
+    });
+
+    t.test('%m{0,1} should behave like a dummy layout', (assert) => {
+      const eventWithSeveralDataEntry = JSON.parse(JSON.stringify(event));
+      eventWithSeveralDataEntry.data = [
+        'This %s a %s like other ones',
+        "isn't",
+        'test',
+      ];
+      testPattern(
+        assert,
+        layout,
+        eventWithSeveralDataEntry,
+        tokens,
+        '%m{0,1}',
+        'This %s a %s like other ones'
+      );
+      assert.end();
+    });
+
+    t.test('%m{1,2} should only consider data.slice(1, 2)', (assert) => {
+      const eventWithSeveralDataEntry = JSON.parse(JSON.stringify(event));
+      eventWithSeveralDataEntry.data = [
+        'This %s a %s like other ones',
+        "isn't",
+        'test',
+      ];
+      testPattern(
+        assert,
+        layout,
+        eventWithSeveralDataEntry,
+        tokens,
+        '%m{1,2}',
+        "isn't"
+      );
+      assert.end();
+    });
+
+    t.test(
+      '%m{0,-1} should consider the whole data except the last element',
+      (assert) => {
+        const eventWithSeveralDataEntry = JSON.parse(JSON.stringify(event));
+        eventWithSeveralDataEntry.data = [
+          'This %s a %s like %s ones',
+          "isn't",
+          'test',
+          'other',
+          "won't be considered in call to util.format",
+        ];
+        testPattern(
+          assert,
+          layout,
+          eventWithSeveralDataEntry,
+          tokens,
+          '%m{0,-1}',
+          "This isn't a test like other ones"
+        );
+        assert.end();
+      }
+    );
+
     t.test('%n should output a new line', (assert) => {
       testPattern(assert, layout, event, tokens, '%n', EOL);
       assert.end();