Ensure presence of libvips before invoking node-gyp

docs/changelog.md

@@ -6,6 +6,8 @@ Requires libvips v8.10.6
 
 ### v0.28.3 - TBD
 
+* Ensure presence of libvips, vendored or global, before invoking node-gyp.
+
 * Skip shrink-on-load for multi-page WebP.
   [#2714](https://github.com/lovell/sharp/issues/2714)
 

install/can-compile.js

@@ -0,0 +1,11 @@
+'use strict';
+
+const libvips = require('../lib/libvips');
+
+try {
+  if (!(libvips.useGlobalLibvips() || libvips.hasVendoredLibvips())) {
+    process.exitCode = 1;
+  }
+} catch (err) {
+  process.exitCode = 1;
+}

install/libvips.js

@@ -43,7 +43,6 @@ const fail = function (err) {
   if (err.code === 'EACCES') {
     libvips.log('Are you trying to install as a root or sudo user? Try again with the --unsafe-perm flag');
   }
-  libvips.log('Attempting to build from source via node-gyp but this may fail due to the above error');
   libvips.log('Please see https://sharp.pixelplumbing.com/install for required dependencies');
   process.exit(1);
 };

package.json

@@ -79,7 +79,7 @@
     "Michael Nutt <michael@nutt.im>"
   ],
   "scripts": {
-    "install": "(node install/libvips && node install/dll-copy && prebuild-install) || (node-gyp rebuild && node install/dll-copy)",
+    "install": "(node install/libvips && node install/dll-copy && prebuild-install) || (node install/can-compile && node-gyp rebuild && node install/dll-copy)",
     "clean": "rm -rf node_modules/ build/ vendor/ .nyc_output/ coverage/ test/fixtures/output.*",
     "test": "npm run test-lint && npm run test-unit && npm run test-licensing",
     "test-lint": "semistandard && cpplint",