Better try statement tree shaking (#3166)

* Do not consider catch clause side-effects, better respect false try-catch-optimization flag

* Suppress trailing blank lines in switch statements

* Slightly improve coverage

* Omit side-effect free cases in switch-statements

* Improve coverage

* Differentiate between break and continue inside switch statements

* Update dependencies. Only log that the license has updated when it
actually has and add instructions to commit it.

* Separate break and continue statements in execution context

package.json

@@ -73,23 +73,23 @@
     "@types/micromatch": "^3.1.0",
     "@types/minimist": "^1.2.0",
     "acorn-import-meta": "^1.0.0",
-    "acorn-jsx": "^5.0.2",
+    "acorn-jsx": "^5.1.0",
     "acorn-walk": "^7.0.0",
     "buble": "^0.19.8",
     "chokidar": "^2.1.8",
     "codecov": "^3.6.1",
     "console-group": "^0.3.3",
-    "core-js": "^3.2.1",
+    "core-js": "^3.3.2",
     "cross-os": "^1.3.0",
     "date-time": "^3.1.0",
     "es5-shim": "^4.5.13",
     "es6-shim": "^0.35.5",
     "eslint": "^6.5.1",
     "eslint-plugin-import": "^2.18.2",
-    "execa": "^2.1.0",
+    "execa": "^3.1.0",
     "fixturify": "^1.2.0",
     "hash.js": "^1.1.7",
-    "husky": "^3.0.8",
+    "husky": "^3.0.9",
     "is-reference": "^1.1.4",
     "lint-staged": "^9.4.2",
     "locate-character": "^2.0.5",
@@ -104,7 +104,7 @@
     "pretty-ms": "^5.0.0",
     "require-relative": "^0.8.7",
     "requirejs": "^2.3.6",
-    "rollup": "^1.23.1",
+    "rollup": "^1.24.0",
     "rollup-plugin-alias": "^2.0.1",
     "rollup-plugin-buble": "^0.19.8",
     "rollup-plugin-commonjs": "^10.1.0",
@@ -122,8 +122,8 @@
     "source-map": "^0.6.1",
     "source-map-support": "^0.5.13",
     "sourcemap-codec": "^1.4.6",
-    "systemjs": "^6.1.3",
-    "terser": "^4.3.8",
+    "systemjs": "^6.1.4",
+    "terser": "^4.3.9",
     "tslib": "^1.10.0",
     "tslint": "^5.20.0",
     "turbocolor": "^2.6.1",

rollup.config.js

@@ -95,18 +95,20 @@ function generateLicenseFile(dependencies) {
 			return text;
 		})
 		.join('\n---------------------------------------\n\n');
-	fs.writeFileSync(
-		'LICENSE.md',
+	const licenseText =
 		`# Rollup core license\n` +
-			`Rollup is released under the MIT license:\n\n` +
-			coreLicense +
-			`\n# Licenses of bundled dependencies\n` +
-			`The published Rollup artifact additionally contains code with the following licenses:\n` +
-			`${Array.from(licenses).join(', ')}\n\n` +
-			`# Bundled dependencies:\n` +
-			dependencyLicenseTexts
-	);
-	console.log('LICENSE.md updated.');
+		`Rollup is released under the MIT license:\n\n` +
+		coreLicense +
+		`\n# Licenses of bundled dependencies\n` +
+		`The published Rollup artifact additionally contains code with the following licenses:\n` +
+		`${Array.from(licenses).join(', ')}\n\n` +
+		`# Bundled dependencies:\n` +
+		dependencyLicenseTexts;
+	const existingLicenseText = fs.readFileSync('LICENSE.md', 'utf8');
+	if (existingLicenseText !== licenseText) {
+		fs.writeFileSync('LICENSE.md', licenseText);
+		console.warn('LICENSE.md updated. You should commit the updated file.');
+	}
 }
 
 const expectedAcornImport = "import acorn__default, { Parser } from 'acorn';";

src/ast/ExecutionContext.ts

@@ -3,7 +3,8 @@ import { PathTracker } from './utils/PathTracker';
 import ThisVariable from './variables/ThisVariable';
 
 interface ExecutionContextIgnore {
-	breakStatements: boolean;
+	breaks: boolean;
+	continues: boolean;
 	labels: Set<string>;
 	returnAwaitYield: boolean;
 }
@@ -39,7 +40,8 @@ export function createHasEffectsContext(): HasEffectsContext {
 		breakFlow: BREAKFLOW_NONE,
 		called: new PathTracker(),
 		ignore: {
-			breakStatements: false,
+			breaks: false,
+			continues: false,
 			labels: new Set(),
 			returnAwaitYield: false
 		},

src/ast/nodes/ArrowFunctionExpression.ts

@@ -58,7 +58,8 @@ export default class ArrowFunctionExpression extends NodeBase {
 		}
 		const { ignore, breakFlow } = context;
 		context.ignore = {
-			breakStatements: false,
+			breaks: false,
+			continues: false,
 			labels: new Set(),
 			returnAwaitYield: true
 		};

src/ast/nodes/BreakStatement.ts

@@ -8,7 +8,7 @@ export default class BreakStatement extends StatementBase {
 	type!: NodeType.tBreakStatement;
 
 	hasEffects(context: HasEffectsContext) {
-		if (!(this.label ? context.ignore.labels.has(this.label.name) : context.ignore.breakStatements))
+		if (!(this.label ? context.ignore.labels.has(this.label.name) : context.ignore.breaks))
 			return true;
 		context.breakFlow = new Set([this.label && this.label.name]);
 		return false;

src/ast/nodes/ContinueStatement.ts

@@ -8,7 +8,7 @@ export default class ContinueStatement extends StatementBase {
 	type!: NodeType.tContinueStatement;
 
 	hasEffects(context: HasEffectsContext) {
-		if (!(this.label ? context.ignore.labels.has(this.label.name) : context.ignore.breakStatements))
+		if (!(this.label ? context.ignore.labels.has(this.label.name) : context.ignore.continues))
 			return true;
 		context.breakFlow = new Set([this.label && this.label.name]);
 		return false;

src/ast/nodes/DoWhileStatement.ts

@@ -11,11 +11,13 @@ export default class DoWhileStatement extends StatementBase {
 		if (this.test.hasEffects(context)) return true;
 		const {
 			breakFlow,
-			ignore: { breakStatements }
+			ignore: { breaks, continues }
 		} = context;
-		context.ignore.breakStatements = true;
+		context.ignore.breaks = true;
+		context.ignore.continues = true;
 		if (this.body.hasEffects(context)) return true;
-		context.ignore.breakStatements = breakStatements;
+		context.ignore.breaks = breaks;
+		context.ignore.continues = continues;
 		if (context.breakFlow instanceof Set && context.breakFlow.has(null)) {
 			context.breakFlow = breakFlow;
 		}