chore: filter alias exports in docs (#8782)

tools/dgeni/index.ts

@@ -1,6 +1,7 @@
 import {Package} from 'dgeni';
 import {DocsPrivateFilter} from './processors/docs-private-filter';
 import {Categorizer} from './processors/categorizer';
+import {FilterExportAliases} from './processors/filter-export-aliases';
 import {ComponentGrouper} from './processors/component-grouper';
 import {ReadTypeScriptModules} from 'dgeni-packages/typescript/processors/readTypeScriptModules';
 import {TsParser} from 'dgeni-packages/typescript/services/TsParser';
@@ -47,6 +48,8 @@ const materialPackages = globSync(path.join(sourceDir, 'lib', '*/'))
 
 export const apiDocsPackage = new Package('material2-api-docs', dgeniPackageDeps);
 
+// Processor that filters out aliased exports that should not be shown in the docs.
+apiDocsPackage.processor(new FilterExportAliases());
 
 // Processor that filters out symbols that should not be shown in the docs.
 apiDocsPackage.processor(new DocsPrivateFilter());

tools/dgeni/processors/filter-export-aliases.ts

@@ -0,0 +1,48 @@
+import {DocCollection, Processor} from 'dgeni';
+import {ExportDoc} from 'dgeni-packages/typescript/api-doc-types/ExportDoc';
+import {ModuleDoc} from 'dgeni-packages/typescript/api-doc-types/ModuleDoc';
+
+/**
+ * Processor to filter out Dgeni documents that are export aliases. Keeping them means
+ * that a given document shows up multiple times in the docs.
+ *
+ * ```ts
+ *   export {ObserveContent} from './X';
+ *   export {ObserveContent as CdkObserveContent} from './X';
+ * ```
+ *
+ * This is a common pattern inside of Angular Material, but causes Dgeni to generate
+ * documents for both exports. The second document is identical to the original document and
+ * doesn't even show the aliased name.
+ *
+ * See: https://github.com/angular/dgeni-packages/issues/248
+ */
+export class FilterExportAliases implements Processor {
+  name = 'filter-export-aliases';
+  $runBefore = ['categorizer'];
+
+  $process(docs: DocCollection) {
+    return docs.filter(doc => this.filterAliasExport(doc));
+  }
+
+  private filterAliasExport(doc: ExportDoc) {
+    if (!doc.moduleDoc) {
+      return true;
+    }
+
+    const moduleDoc = doc.moduleDoc as ModuleDoc;
+    const duplicateDocs = moduleDoc.exports.filter(exportDoc => exportDoc.id === doc.id);
+
+    // Remove the current export document if there are multiple Dgeni export documents with the
+    // same document id. If there are multiple docs with the same id, we can assume that this doc
+    // is an alias export.
+    if (duplicateDocs && duplicateDocs.length > 1) {
+      moduleDoc.exports.splice(
+        moduleDoc.exports.findIndex(exportDoc => exportDoc.id === doc.id), 1);
+      return false;
+    }
+
+    return true;
+  }
+
+}