add evaluation to optional chaining

webpack · Jul 19, 2020 · abd8905 · abd8905
1 parent 52fa851
commit abd8905
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Showing 5 changed files with 64 additions and 4 deletions.
diff --git a/lib/ConstPlugin.js b/lib/ConstPlugin.js
@@ -10,6 +10,8 @@ const ConstDependency = require("./dependencies/ConstDependency");
 const { evaluateToString } = require("./javascript/JavascriptParserHelpers");
 const { parseResource } = require("./util/identifier");
 
+/** @typedef {import("estree").Expression} ExpressionNode */
+/** @typedef {import("estree").Super} SuperNode */
 /** @typedef {import("./Compiler")} Compiler */
 
 const collectDeclaration = (declarations, pattern) => {
@@ -358,6 +360,51 @@ class ConstPlugin {
 							}
 						}
 					);
+					parser.hooks.optionalChaining.tap("ConstPlugin", expr => {
+						const optionalExpressionsStack = [];
+						/** @type {ExpressionNode|SuperNode} */
+						let next;
+
+						if (expr.expression.type === "CallExpression") {
+							next = expr.expression.callee;
+						} else {
+							next = expr.expression;
+						}
+
+						while (next.type === "MemberExpression") {
+							if (next.optional) {
+								optionalExpressionsStack.push(next.object);
+							}
+							next = next.object;
+						}
+
+						while (optionalExpressionsStack.length) {
+							const expression = optionalExpressionsStack.pop();
+							const evaluated = parser.evaluateExpression(expression);
+
+							if (evaluated && evaluated.asNullish()) {
+								// ------------------------------------------
+								//
+								// Given the following code:
+								//
+								//   nullishMemberChain?.a.b();
+								//
+								// the generated code is:
+								//
+								//   null; // or undefined; if evaluated to undefined
+								//
+								// ------------------------------------------
+								//
+								const dep = new ConstDependency(
+									evaluated.isUndefined() ? "undefined" : "null",
+									expr.range
+								);
+								dep.loc = expr.loc;
+								parser.state.module.addPresentationalDependency(dep);
+								return true;
+							}
+						}
+					});
 					parser.hooks.evaluateIdentifier
 						.for("__resourceQuery")
 						.tap("ConstPlugin", expr => {

diff --git a/lib/javascript/JavascriptParser.js b/lib/javascript/JavascriptParser.js
@@ -260,6 +260,8 @@ class JavascriptParser extends Parser {
 						"members"
 					])
 			),
+			/** @type {SyncBailHook<[ChainExpressionNode], boolean | void>} */
+			optionalChaining: new SyncBailHook(["optionalChaining"]),
 			/** @type {HookMap<SyncBailHook<[ExpressionNode], boolean | void>>} */
 			new: new HookMap(() => new SyncBailHook(["expression"])),
 			/** @type {SyncBailHook<[MetaPropertyNode], boolean | void>} */
@@ -2352,10 +2354,14 @@ class JavascriptParser extends Parser {
 	 * @param {ChainExpressionNode} expression expression
 	 */
 	walkChainExpression(expression) {
-		if (expression.expression.type === "CallExpression") {
-			this.walkCallExpression(expression.expression);
-		} else {
-			this.walkMemberExpression(expression.expression);
+		const result = this.hooks.optionalChaining.call(expression);
+
+		if (result === undefined) {
+			if (expression.expression.type === "CallExpression") {
+				this.walkCallExpression(expression.expression);
+			} else {
+				this.walkMemberExpression(expression.expression);
+			}
 		}
 	}
 

diff --git a/test/cases/parsing/optional-chaining/a.js b/test/cases/parsing/optional-chaining/a.js
@@ -0,0 +1 @@
+module.exports = 1;
diff --git a/test/cases/parsing/optional-chaining/index.js b/test/cases/parsing/optional-chaining/index.js
@@ -0,0 +1,5 @@
+it("should handle optional members", () => {
+	expect(
+		module.hot?.accept((() => {throw new Error("fail")})())
+	).toBe(null);
+});
diff --git a/types.d.ts b/types.d.ts
@@ -3272,6 +3272,7 @@ declare abstract class JavascriptParser extends Parser {
 				boolean | void
 			>
 		>;
+		optionalChaining: SyncBailHook<[ChainExpression], boolean | void>;
 		new: HookMap<SyncBailHook<[Expression], boolean | void>>;
 		metaProperty: SyncBailHook<[MetaProperty], boolean | void>;
 		expression: HookMap<SyncBailHook<[Expression], boolean | void>>;