lib: refactor policy code for readability

Simplify a few particularly quirky bits of code, and add
whitespace for readability.

PR-URL: #25629
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

Author: addaleax

lib/internal/policy/manifest.js

@@ -22,19 +22,23 @@ const kReactions = new SafeWeakMap();
 const kRelativeURLStringPattern = /^\.{0,2}\//;
 const { shouldAbortOnUncaughtException } = internalBinding('config');
 const { abort, exit, _rawDebug } = process;
+
 function REACTION_THROW(error) {
   throw error;
 }
+
 function REACTION_EXIT(error) {
   REACTION_LOG(error);
   if (shouldAbortOnUncaughtException) {
     abort();
   }
   exit(1);
 }
+
 function REACTION_LOG(error) {
   _rawDebug(error.stack);
 }
+
 class Manifest {
   constructor(obj, manifestURL) {
     const integrities = {
@@ -44,6 +48,7 @@ class Manifest {
       __proto__: null,
       integrity: REACTION_THROW,
     };
+
     if (obj.onerror) {
       const behavior = obj.onerror;
       if (behavior === 'throw') {
@@ -55,8 +60,10 @@ class Manifest {
         throw new ERR_MANIFEST_UNKNOWN_ONERROR(behavior);
       }
     }
+
     kReactions.set(this, Object.freeze(reactions));
     const manifestEntries = entries(obj.resources);
+
     for (var i = 0; i < manifestEntries.length; i++) {
       let url = manifestEntries[i][0];
       const integrity = manifestEntries[i][1].integrity;
@@ -65,10 +72,12 @@ class Manifest {
         if (RegExpTest(kRelativeURLStringPattern, url)) {
           url = new URL(url, manifestURL).href;
         }
+
         const sri = Object.freeze(SRI.parse(integrity));
         if (url in integrities) {
           const old = integrities[url];
           let mismatch = false;
+
           if (old.length !== sri.length) {
             mismatch = true;
           } else {
@@ -85,6 +94,7 @@ class Manifest {
               break compare;
             }
           }
+
           if (mismatch) {
             throw new ERR_MANIFEST_INTEGRITY_MISMATCH(url);
           }
@@ -96,10 +106,12 @@ class Manifest {
     kIntegrities.set(this, integrities);
     Object.freeze(this);
   }
+
   assertIntegrity(url, content) {
     debug(`Checking integrity of ${url}`);
     const integrities = kIntegrities.get(this);
     const realIntegrities = new Map();
+
     if (integrities && url in integrities) {
       const integrityEntries = integrities[url];
       // Avoid clobbered Symbol.iterator
@@ -122,6 +134,7 @@ class Manifest {
     kReactions.get(this).integrity(error);
   }
 }
+
 // Lock everything down to avoid problems even if reference is leaked somehow
 Object.setPrototypeOf(Manifest, null);
 Object.setPrototypeOf(Manifest.prototype, null);

lib/internal/policy/sri.js

@@ -18,29 +18,27 @@ const { freeze } = Object;
 Object.seal(kSRIPattern);
 const kAllWSP = new RegExp(`^${kWSP}*$`);
 Object.seal(kAllWSP);
+
 const RegExpExec = Function.call.bind(RegExp.prototype.exec);
 const RegExpTest = Function.call.bind(RegExp.prototype.test);
 const StringSlice = Function.call.bind(String.prototype.slice);
-const {
-  Buffer: {
-    from: BufferFrom
-  }
-} = require('buffer');
+
+const BufferFrom = require('buffer').Buffer.from;
 const { defineProperty } = Object;
+
 const parse = (str) => {
   kSRIPattern.lastIndex = 0;
   let prevIndex = 0;
-  let match = RegExpExec(kSRIPattern, str);
+  let match;
   const entries = [];
-  while (match) {
+  while (match = RegExpExec(kSRIPattern, str)) {
     if (match.index !== prevIndex) {
       throw new ERR_SRI_PARSE(str, prevIndex);
     }
-    if (entries.length > 0) {
-      if (match[1] === '') {
-        throw new ERR_SRI_PARSE(str, prevIndex);
-      }
+    if (entries.length > 0 && match[1] === '') {
+      throw new ERR_SRI_PARSE(str, prevIndex);
     }
+
     // Avoid setters being fired
     defineProperty(entries, entries.length, {
       enumerable: true,
@@ -53,8 +51,8 @@ const parse = (str) => {
       })
     });
     prevIndex = prevIndex + match[0].length;
-    match = RegExpExec(kSRIPattern, str);
   }
+
   if (prevIndex !== str.length) {
     if (!RegExpTest(kAllWSP, StringSlice(str, prevIndex))) {
       throw new ERR_SRI_PARSE(str, prevIndex);

lib/internal/process/policy.js

@@ -5,13 +5,15 @@ const {
 } = require('internal/errors').codes;
 const { Manifest } = require('internal/policy/manifest');
 let manifest;
+
 module.exports = Object.freeze({
   __proto__: null,
   setup(src, url) {
     if (src === null) {
       manifest = null;
       return;
     }
+
     const json = JSON.parse(src, (_, o) => {
       if (o && typeof o === 'object') {
         Reflect.setPrototypeOf(o, null);
@@ -21,12 +23,14 @@ module.exports = Object.freeze({
     });
     manifest = new Manifest(json, url);
   },
+
   get manifest() {
     if (typeof manifest === 'undefined') {
       throw new ERR_MANIFEST_TDZ();
     }
     return manifest;
   },
+
   assertIntegrity(moduleURL, content) {
     this.manifest.matchesIntegrity(moduleURL, content);
   }