Improve AST garbage collection

LICENSE.md

@@ -247,6 +247,23 @@ Repository: jonschlinkert/fill-range
 
 ---------------------------------------
 
+## flru
+License: MIT
+By: Luke Edwards
+Repository: lukeed/flru
+
+> MIT License
+> 
+> Copyright (c) Luke Edwards <luke.edwards05@gmail.com> (lukeed.com)
+> 
+> Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+> 
+> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+> 
+> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+---------------------------------------
+
 ## glob-parent
 License: ISC
 By: Gulp Team, Elan Shanker, Blaine Bublitz

browser/LICENSE.md

@@ -88,6 +88,23 @@ Repository: https://github.com/acornjs/acorn.git
 
 ---------------------------------------
 
+## flru
+License: MIT
+By: Luke Edwards
+Repository: lukeed/flru
+
+> MIT License
+> 
+> Copyright (c) Luke Edwards <luke.edwards05@gmail.com> (lukeed.com)
+> 
+> Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+> 
+> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+> 
+> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+---------------------------------------
+
 ## hash.js
 License: MIT
 By: Fedor Indutny

package.json

@@ -90,6 +90,7 @@
     "eslint-plugin-prettier": "^4.2.1",
     "eslint-plugin-unicorn": "^44.0.2",
     "fixturify": "^2.1.1",
+    "flru": "^1.0.2",
     "fs-extra": "^10.1.0",
     "github-api": "^3.4.0",
     "hash.js": "^1.1.7",

src/Graph.ts

@@ -1,4 +1,5 @@
 import * as acorn from 'acorn';
+import flru from 'flru';
 import type ExternalModule from './ExternalModule';
 import Module from './Module';
 import { ModuleLoader, type UnresolvedModule } from './ModuleLoader';
@@ -52,6 +53,7 @@ function normalizeEntryModules(
 
 export default class Graph {
 	readonly acornParser: typeof acorn.Parser;
+	readonly astLru = flru<acorn.Node>(5);
 	readonly cachedModules = new Map<string, ModuleJSON>();
 	readonly deoptimizationTracker = new PathTracker();
 	entryModules: Module[] = [];
@@ -63,6 +65,7 @@ export default class Graph {
 	readonly pluginDriver: PluginDriver;
 	readonly pureFunctions: PureFunctions;
 	readonly scope = new GlobalScope();
+	useCache = false;
 	readonly watchFiles: Record<string, true> = Object.create(null);
 	watchMode = false;
 
@@ -73,6 +76,7 @@ export default class Graph {
 
 	constructor(private readonly options: NormalizedInputOptions, watcher: RollupWatcher | null) {
 		if (options.cache !== false) {
+			this.useCache = true;
 			if (options.cache?.modules) {
 				for (const module of options.cache.modules) this.cachedModules.set(module.id, module);
 			}

src/Module.ts

@@ -770,10 +770,7 @@ export default class Module {
 		this.transformDependencies = transformDependencies;
 		this.customTransformCache = customTransformCache;
 		this.updateOptions(moduleOptions);
-
-		if (!ast) {
-			ast = this.tryParse();
-		}
+		const moduleAst = ast || this.tryParse();
 
 		timeEnd('generate ast', 3);
 		timeStart('analyze ast', 3);
@@ -821,16 +818,34 @@ export default class Module {
 
 		this.scope = new ModuleScope(this.graph.scope, this.astContext);
 		this.namespace = new NamespaceVariable(this.astContext);
-		this.ast = new Program(ast, { context: this.astContext, type: 'Module' }, this.scope);
-		this.info.ast = ast;
+		this.ast = new Program(moduleAst, { context: this.astContext, type: 'Module' }, this.scope);
+
+		// Assign AST directly if has existing one as there's no way to drop it from memory.
+		// If cache is enabled, also assign directly as otherwise it takes more CPU and memory to re-compute.
+		if (ast || this.graph.useCache) {
+			this.info.ast = moduleAst;
+		} else {
+			// Make lazy and apply LRU cache to not hog the memory
+			Object.defineProperty(this.info, 'ast', {
+				get: () => {
+					if (this.graph.astLru.has(fileName)) {
+						return this.graph.astLru.get(fileName)!;
+					} else {
+						const parsedAst = this.tryParse();
+						this.graph.astLru.set(fileName, parsedAst);
+						return parsedAst;
+					}
+				}
+			});
+		}
 
 		timeEnd('analyze ast', 3);
 	}
 
 	toJSON(): ModuleJSON {
 		return {
 			assertions: this.info.assertions,
-			ast: this.ast!.esTreeNode,
+			ast: this.info.ast!,
 			code: this.info.code!,
 			customTransformCache: this.customTransformCache,
 			// eslint-disable-next-line unicorn/prefer-spread

src/ModuleLoader.ts

@@ -541,7 +541,7 @@ export class ModuleLoader {
 				module,
 				typeof dynamicImport.argument === 'string'
 					? dynamicImport.argument
-					: dynamicImport.argument.esTreeNode,
+					: dynamicImport.argument.esTreeNode!,
 				module.id,
 				getAssertionsFromImportExpression(dynamicImport.node)
 			);

src/ast/nodes/ImportExpression.ts

@@ -14,7 +14,12 @@ import type ChildScope from '../scopes/ChildScope';
 import type NamespaceVariable from '../variables/NamespaceVariable';
 import type * as NodeType from './NodeType';
 import type ObjectExpression from './ObjectExpression';
-import { type ExpressionNode, type IncludeChildren, NodeBase } from './shared/Node';
+import {
+	type ExpressionNode,
+	type GenericEsTreeNode,
+	type IncludeChildren,
+	NodeBase
+} from './shared/Node';
 
 interface DynamicImportMechanism {
 	left: string;
@@ -57,6 +62,11 @@ export default class ImportExpression extends NodeBase {
 		this.context.addDynamicImport(this);
 	}
 
+	parseNode(esTreeNode: GenericEsTreeNode): void {
+		// Keep the source AST to be used by renderDynamicImport
+		super.parseNode(esTreeNode, ['source']);
+	}
+
 	render(code: MagicString, options: RenderOptions): void {
 		const {
 			snippets: { _, getDirectReturnFunction, getObject, getPropertyAccess }

src/ast/nodes/shared/Node.ts

@@ -31,7 +31,7 @@ export interface Node extends Entity {
 	annotations?: acorn.Comment[];
 	context: AstContext;
 	end: number;
-	esTreeNode: GenericEsTreeNode;
+	esTreeNode: GenericEsTreeNode | null;
 	included: boolean;
 	keys: string[];
 	needsBoundaries?: boolean;
@@ -119,7 +119,7 @@ export class NodeBase extends ExpressionEntity implements ExpressionNode {
 	declare annotations?: acorn.Comment[];
 	context: AstContext;
 	declare end: number;
-	esTreeNode: acorn.Node;
+	esTreeNode: acorn.Node | null;
 	keys: string[];
 	parent: Node | { context: AstContext; type: string };
 	declare scope: ChildScope;
@@ -140,10 +140,13 @@ export class NodeBase extends ExpressionEntity implements ExpressionNode {
 	constructor(
 		esTreeNode: GenericEsTreeNode,
 		parent: Node | { context: AstContext; type: string },
-		parentScope: ChildScope
+		parentScope: ChildScope,
+		keepEsTreeNode = false
 	) {
 		super();
-		this.esTreeNode = esTreeNode;
+		// Nodes can opt-in to keep the AST if needed during the build pipeline.
+		// Avoid true when possible as large AST takes up memory.
+		this.esTreeNode = keepEsTreeNode ? esTreeNode : null;
 		this.keys = keys[esTreeNode.type] || getAndCreateKeys(esTreeNode);
 		this.parent = parent;
 		this.context = parent.context;
@@ -243,7 +246,7 @@ export class NodeBase extends ExpressionEntity implements ExpressionNode {
 		}
 	}
 
-	parseNode(esTreeNode: GenericEsTreeNode): void {
+	parseNode(esTreeNode: GenericEsTreeNode, keepEsTreeNodeKeys?: string[]): void {
 		for (const [key, value] of Object.entries(esTreeNode)) {
 			// That way, we can override this function to add custom initialisation and then call super.parseNode
 			if (this.hasOwnProperty(key)) continue;
@@ -262,14 +265,20 @@ export class NodeBase extends ExpressionEntity implements ExpressionNode {
 					(this as GenericEsTreeNode)[key].push(
 						child === null
 							? null
-							: new (this.context.getNodeConstructor(child.type))(child, this, this.scope)
+							: new (this.context.getNodeConstructor(child.type))(
+									child,
+									this,
+									this.scope,
+									keepEsTreeNodeKeys?.includes(key)
+							  )
 					);
 				}
 			} else {
 				(this as GenericEsTreeNode)[key] = new (this.context.getNodeConstructor(value.type))(
 					value,
 					this,
-					this.scope
+					this.scope,
+					keepEsTreeNodeKeys?.includes(key)
 				);
 			}
 		}

test/function/samples/plugin-module-information-no-cache/_config.js

@@ -0,0 +1,65 @@
+const assert = require('node:assert');
+const path = require('node:path');
+
+const ID_MAIN = path.join(__dirname, 'main.js');
+
+module.exports = {
+	description: 'handles accessing module information via plugins with cache disabled',
+	options: {
+		cache: false,
+		plugins: [
+			{
+				renderStart() {
+					const info = this.getModuleInfo(ID_MAIN);
+					const ast = {
+						type: 'Program',
+						start: 0,
+						end: 19,
+						body: [
+							{
+								type: 'ExportDefaultDeclaration',
+								start: 0,
+								end: 18,
+								declaration: {
+									type: 'Literal',
+									start: 15,
+									end: 17,
+									value: 42,
+									raw: '42'
+								}
+							}
+						],
+						sourceType: 'module'
+					};
+					assert.deepStrictEqual(JSON.parse(JSON.stringify(info)), {
+						assertions: {},
+						ast,
+						code: 'export default 42;\n',
+						dynamicallyImportedIdResolutions: [],
+						dynamicallyImportedIds: [],
+						dynamicImporters: [],
+						exportedBindings: {
+							'.': ['default']
+						},
+						exports: ['default'],
+						hasDefaultExport: true,
+						id: ID_MAIN,
+						implicitlyLoadedAfterOneOf: [],
+						implicitlyLoadedBefore: [],
+						importedIdResolutions: [],
+						importedIds: [],
+						importers: [],
+						isEntry: true,
+						isExternal: false,
+						isIncluded: true,
+						meta: {},
+						moduleSideEffects: true,
+						syntheticNamedExports: false
+					});
+					// Call AST again to ensure line coverage for cached getter
+					assert.deepStrictEqual(JSON.parse(JSON.stringify(info.ast)), ast);
+				}
+			}
+		]
+	}
+};

test/function/samples/plugin-module-information-no-cache/main.js

@@ -0,0 +1 @@
+export default 42;