[build] Test building a "use strict" safe package

- Adds a test to the CI pipeline that builds a "typical" consolidated
  Highlight.js package from the full NPM source and then checks that
  that build actually executes without errors

Related to highlightjs#2247.

.travis.yml

@@ -3,7 +3,8 @@ node_js:
   - "lts/*"
   - "node"
 env:
-  -
+  # we current only test "use strict" for our NPM builds
+  - TEST_BUILDING_USE_STRICT_BUNDLE=1
   - BROWSER=1
   - BROWSER=1 NOCOMPRESS=1
 script:
@@ -22,6 +23,14 @@ script:
 
     node tools/build.js $BUILD_PARAMS
 
+    # test that our build is "use strict" safe for use with packaging
+    # systems importing our source thru ES6 modules (rollup, etc.)
+    if [ "x$TEST_BUILDING_USE_STRICT_BUNDLE" = "x1" ]; then
+      ./node_modules/.bin/rollup -c test/builds/rollup_import_via_commonjs.js
+      node build/bundle.js || exit 1
+      rm build/bundle.js
+    fi
+
     if [ "x$BROWSER" = "x1" ]; then
       npm run test-browser
     else

CHANGES.md

@@ -7,6 +7,7 @@ New styles:
   none.
 
 Improvements:
+- ehh(build) Add CI check for building a "use strict" safe rollup package from NPM builds (#2247) [Josh Goebel][]
 - enhance(css) Improve @rule highlighting, including properties (#2241) [Josh Goebel][]
 - enhance(css) Improve highlighting of numbers inside expr/func `calc(2px+3px)` (#2241)
 - enhance(scss) Pull some of the CSS improvements back into SCSS (#2241)

package.json

@@ -30,9 +30,9 @@
     "node": "*"
   },
   "devDependencies": {
+    "bluebird": "^3.5.5",
     "cli-table": "^0.3.1",
     "colors": "^1.1.2",
-    "bluebird": "^3.5.5",
     "commander": "^4.0.0",
     "del": "^5.1.0",
     "gear": "github:highlightjs/gear",
@@ -42,6 +42,8 @@
     "jsdom": "^15.1.1",
     "lodash": "^4.17.15",
     "mocha": "^6.2.0",
+    "rollup": "^1.26.2",
+    "rollup-plugin-commonjs": "^10.1.0",
     "should": "^13.2.3",
     "tiny-worker": "^2.3.0"
   }

test/builds/package.js

@@ -0,0 +1,11 @@
+/*
+This file is used by import_via_commonjs.js to build a single "package"
+and acts as a sanity check that all our code is "use strict" safe
+
+See .travis.yml
+*/
+
+import hljs from '../../build/lib/index.js';
+
+hljs.highlight("cpp","/* test */")
+console.log("Rollup built package works.")