Emit 'warning' event for non-critical problems #2032

docs/changelog.md

@@ -24,6 +24,9 @@ Requires libvips v8.9.1
 * Add experimental `sharpness` calculation to `stats()` response.
   [#2251](https://github.com/lovell/sharp/issues/2251)
 
+* Emit `warning` event for non-critical processing problems.
+  [#2032](https://github.com/lovell/sharp/issues/2032)
+
 ### v0.25.3 - 17th May 2020
 
 * Ensure libvips is initialised only once, improves worker thread safety.

lib/constructor.js

@@ -45,8 +45,13 @@ const debuglog = util.debuglog('sharp');
  * JPEG, PNG, WebP or TIFF format image data can be streamed out from this object.
  * When using Stream based output, derived attributes are available from the `info` event.
  *
+ * Non-critical problems encountered during processing are emitted as `warning` events.
+ *
  * Implements the [stream.Duplex](http://nodejs.org/api/stream.html#stream_class_stream_duplex) class.
  *
+ * @emits Sharp#info
+ * @emits Sharp#warning
+ *
  * @example
  * sharp('input.jpg')
  *   .resize(300, 200)
@@ -230,7 +235,10 @@ const Sharp = function (input, options) {
     linearA: 1,
     linearB: 0,
     // Function to notify of libvips warnings
-    debuglog: debuglog,
+    debuglog: warning => {
+      this.emit('warning', warning);
+      debuglog(warning);
+    },
     // Function to notify of queue length changes
     queueListener: function (queueLength) {
       Sharp.queue.emit('change', queueLength);

test/unit/failOnError.js

@@ -19,11 +19,17 @@ describe('failOnError', function () {
       });
   });
 
-  it('handles truncated PNG', function (done) {
+  it('handles truncated PNG, emits warnings', function (done) {
+    let isWarningEmitted = false;
     sharp(fixtures.inputPngTruncated, { failOnError: false })
+      .on('warning', function (warning) {
+        assert.strictEqual('not enough data', warning);
+        isWarningEmitted = true;
+      })
       .resize(320, 240)
       .toBuffer(function (err, data, info) {
         if (err) throw err;
+        assert.strictEqual(true, isWarningEmitted);
         assert.strictEqual('png', info.format);
         assert.strictEqual(320, info.width);
         assert.strictEqual(240, info.height);