Comment the code a bit to explain the approach. Add npmignore

.npmignore

@@ -0,0 +1,2 @@
+example
+yarn.lock

index.js

@@ -5,11 +5,13 @@ const { ExtractGQL } = require('persistgraphql/lib/src/ExtractGQL');
 const queryTransformers = require('persistgraphql/lib/src/queryTransformers');
 const loadModuleRecursively = require('./load-module-recursively');
 
-module.exports = function graphQLpersistedDocumentLoader(content) {
+module.exports = function graphQLPersistedDocumentLoader(content) {
   const deps = [];
   const context = this;
   const options = loaderUtils.getOptions(this) || {};
 
+  // Create a fake sandbox to intercept the query dependencies when
+  // executing the generated code from the graphql-tag loader.
   const sandbox = {
     require(file) {
       deps.push(new Promise((resolve, reject) => {
@@ -27,24 +29,38 @@ module.exports = function graphQLpersistedDocumentLoader(content) {
       exports: null
     }
   };
+  // Run the graphql-tag loader generated code to capture the dependencies.
   vm.runInNewContext(content, sandbox);
 
+  // Get the query document source from the exported module, and
+  // save it so that we can use it from other modules that may depend on
+  // this one.
   const doc = sandbox.module.exports;
   this._module._graphQLQuerySource = doc.loc.source.body;
 
   if (deps.length === 0) {
+    // If no deps, just try to generate the document id from the
+    // source returned from graphql-tag loader result. This will
+    // add an id only if the source contains an operation.
     content = tryAddDocumentId(options, content, this._module._graphQLQuerySource);
     return content;
   }
 
   const callback = this.async();
 
+  // If we have dependencies, we retrieve their query sources and
+  // concatenate them with the one from this module, to create the
+  // full query source.
   Promise.all(deps).then((modules) => {
     modules.forEach((mod, index) => {
       this._module._graphQLQuerySource += mod.module._graphQLQuerySource;
     });
 
     try {
+      // Now that we have all our dependencies' sources concatenated
+      // with this module's query source, we can send all that to
+      // generate the document id, if the resulting source
+      // is for an operation.
       content = tryAddDocumentId(options, content, this._module._graphQLQuerySource);
     } catch (e) {
       callback(e);