minifying alters DataFactory types

[ericprud]

Problem

using a minifier changes the names of the classes that extend Term.

Reproduced

1. Add N3.js to a vanilla module:
   MyModule.js

MyModule = (function () {
  let n3 = require('n3')
  return {
    some: "stuff",
    N3: n3
  }
})()

if (typeof require !== 'undefined' && typeof exports !== 'undefined')
  module.exports = MyModule

2. package it with browserify or webpack:
   webpack.config.js

const path = require('path');
const TerserPlugin = require('terser-webpack-plugin');
const webpack = require("webpack");

module.exports = {
  entry: {
    "my-webapp-webpack": "./MyModule.js",
    "my-webapp-webpack.min": "./MyModule.js",
  },
  output: {
    filename: "[name].js",
    path: path.resolve(__dirname, 'browser'),
  },
  optimization: {
    minimize: true,
    minimizer: [new TerserPlugin({
      terserOptions: {
        "keep_classnames": false
      },
      include: /\.min\.js$/
    })]
  },
};

3. Call it from some HTML:
   MyWebApp.html

    <script src="browser/my-webapp-webpack.min.js"></script>
    <scritp>
let f = MyModule.N3.DataFactory
const myQuad = f.quad(
  f.blankNode('s'),
  f.namedNode('http://a.example/p'),
  f.namepNode('http://a.example/o'),
  f.defaultGraph(),
);
console.log("quad:", JSON.stringify(myQuad))
console.log("subject termType:", myQuad.subject.termType)
    </script>

4. check console; should see that the termTypes have been minified:

quad: {
  "subject": { "termType": "c", "value": "s" },
  "predicate": { "termType": "f", "value": "http://a.example/p" },
  "object": { "termType": "f", "value": "http://a.example/o" },
  "graph": { "termType": "p", "value": "" }
}
subject termType: c

Solution

There are two solutions: (1) advise users or (2) use static names for Term.typeName.

1 Tell minifier, e.g. terser (was uglifier) not to compress class names:

require('terser').minify(myModuleAsAString, {
  "keep_classnames": true
})

For webpack, that looks like:

  optimization: {
    minimize: true,
    minimizer: [new TerserPlugin({
      terserOptions: {
        "keep_classnames": true
      },
      include: /\.min\.js$/
    })]
  },

2. Make the DataFactory Term.termType getters respond with static text:

--- packages/shex-cli/node_modules/n3/lib/N3DataFactory.js	2019-04-01 07:52:51.652880151 +0200
+++ /tmp/ediff4492TCm	2019-04-01 07:54:07.301991690 +0200
@@ -46,12 +46,19 @@
 
 
 // ## NamedNode constructor
-class NamedNode extends Term {}
+class NamedNode extends Term {
+  get termType() {
+    return 'NamedNode';
+  }
+}
 NamedNode.name = 'NamedNode';
 
 
 // ## Literal constructor
 class Literal extends Term {
+  get termType() {
+    return 'Literal';
+  }
   // ### The text value of this literal
   get value() {
     return this.id.substring(1, this.id.lastIndexOf('"'));
@@ -111,6 +118,10 @@
     super('_:' + name);
   }
 
+  get termType() {
+    return 'BlankNode';
+  }
+
   // ### The name of this blank node
   get value() {
     return this.id.substr(2);
@@ -123,6 +134,10 @@
     super('?' + name);
   }
 
+  get termType() {
+    return 'Variable';
+  }
+
   // ### The name of this variable
   get value() {
     return this.id.substr(1);
@@ -137,6 +152,10 @@
     return DEFAULTGRAPH || this;
   }
 
+  get termType() {
+    return 'DefaultGraph';
+  }
+
   // ### Returns whether this object represents the same term as the other
   equals(other) {
     // If both terms were created by this library,

[RubenVerborgh]

NamedNode.name = 'NamedNode'; should fix that: #135
But I guess this broke with the ES6 rewrite…

Seems like we now need Object.defineProperty(NamedNode, 'name', { value: 'NamedNode' }). Bah.

Not sure which is the best performance-wise.

Maybe I should get rid of inheritance altogether.

[ericprud]

I never figured out how to

x instanceof Term // or NamedNode or whatever

so I wouldn't miss inheritance as a user. There are places where I want to see if something is an RDFJS term but i do that with:

["NamedNode", "BlankNode", "Literal"].indexOf(x.termType) !== -1

Otherwise, maybe modern terser fixes #135?

[SimonShapiro]

I need at least a workaround for this. My use case is to modify ui elements based on the termType, so I need something predictable.

[SimonShapiro]

I'm pleased to report that method 1 above works fine. Thanks. :-)