Install: advanced option to force global libvips #4060

docs/changelog.md

@@ -12,6 +12,9 @@ Requires libvips v8.15.2
   [#4048](https://github.com/lovell/sharp/pull/4048)
   [@ike-gg](https://github.com/ike-gg)
 
+* Install: add advanced option to force use of a globally-installed libvips.
+  [#4060](https://github.com/lovell/sharp/issues/4060)
+
 * Expose `bilinear` resizing kernel (and interpolator).
   [#4061](https://github.com/lovell/sharp/issues/4061)
 

docs/install.md

@@ -103,9 +103,14 @@ and on macOS when running Node.js under Rosetta.
 
 This module will be compiled from source at `npm install` time when:
 
-* a globally-installed libvips is detected (set the `SHARP_IGNORE_GLOBAL_LIBVIPS` environment variable to skip this), or
+* a globally-installed libvips is detected, or
 * when the `npm install --build-from-source` flag is used.
 
+The logic to detect a globally-installed libvips can be skipped by setting the
+`SHARP_IGNORE_GLOBAL_LIBVIPS` (never try to use it) or
+`SHARP_FORCE_GLOBAL_LIBVIPS` (always try to use it, even when missing or outdated)
+environment variables.
+
 Building from source requires:
 
 * C++11 compiler