From 30ca424942d4193154c291866bd52d1aebfd3570 Mon Sep 17 00:00:00 2001
From: Lovell Fuller <github@lovell.info>
Date: Tue, 1 Jan 2019 18:40:09 +0000
Subject: [PATCH] Apply correct forced output when chaining #1528

---
 docs/changelog.md |  3 +++
 lib/output.js     |  4 +++-
 test/unit/io.js   | 11 +++++++++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/docs/changelog.md b/docs/changelog.md
index a1491ebd..9e538e8f 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -9,6 +9,9 @@ Requires libvips v8.7.0.
 * Prevent mutatation of options passed to `jpeg`.
   [#1516](https://github.com/lovell/sharp/issues/1516)
 
+* Ensure forced output format applied correctly when output chaining.
+  [#1528](https://github.com/lovell/sharp/issues/1528)
+
 #### v0.21.1 - 7<sup>th</sup> December 2018
 
 * Install: support `sharp_dist_base_url` npm config, like existing `SHARP_DIST_BASE_URL`.
diff --git a/lib/output.js b/lib/output.js
index a3aad553..f74bfc35 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -541,7 +541,9 @@ function tile (tile) {
  * @returns {Sharp}
  */
 function _updateFormatOut (formatOut, options) {
-  this.options.formatOut = (is.object(options) && options.force === false) ? 'input' : formatOut;
+  if (!(is.object(options) && options.force === false)) {
+    this.options.formatOut = formatOut;
+  }
   return this;
 }
 
diff --git a/test/unit/io.js b/test/unit/io.js
index 5392dbf7..2338501a 100644
--- a/test/unit/io.js
+++ b/test/unit/io.js
@@ -1376,6 +1376,17 @@ describe('Input/output', function () {
       });
   });
 
+  it('Can force output format with output chaining', function () {
+    return sharp(fixtures.inputJpg)
+      .resize(320, 240)
+      .png({ force: true })
+      .jpeg({ force: false })
+      .toBuffer({ resolveWithObject: true })
+      .then(function (out) {
+        assert.strictEqual('png', out.info.format);
+      });
+  });
+
   it('toFormat=JPEG takes precedence over WebP extension', function (done) {
     sharp(fixtures.inputPng)
       .jpeg()