Merge pull request #9 from Microsoft/lint-more

Lint more
microsoft · Nov 29, 2021 · f997150 · f997150
1 parent 29a9097
commit f997150
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Showing 3 changed files with 80 additions and 8 deletions.
diff --git a/packages/dtslint/dtslint.json b/packages/dtslint/dtslint.json
@@ -15,6 +15,7 @@
         "no-redundant-modifiers": true,
         "no-single-declare-module": true,
 		"no-useless-files": true,
+        "prefer-declare-function": true,
         "trim-file": true,
         "unified-signatures": true,
         "void-return": true,

diff --git a/packages/dtslint/src/rules/noRedundantModifiersRule.ts b/packages/dtslint/src/rules/noRedundantModifiersRule.ts
@@ -15,21 +15,27 @@ export class Rule extends Lint.Rules.AbstractRule {
 		if (!sourceFile.isDeclarationFile) {
 			return [];
 		}
+
 		return this.applyWithFunction(sourceFile, walk);
 	}
 }
 
 function walk(ctx: Lint.WalkContext<void>): void {
-	for (const node of ctx.sourceFile.statements) {
+	const { sourceFile } = ctx;
+	for (const node of sourceFile.statements) {
 		if (isDeclare(node)) {
 			if (isExport(node)) {
 				ctx.addFailureAtNode(node, "'export declare' is redundant, just use 'export'.");
 			} else {
-				// Types do not need 'declare'.
-				switch (node.kind) {
-					case ts.SyntaxKind.InterfaceDeclaration:
-					case ts.SyntaxKind.TypeAliasDeclaration:
-						ctx.addFailureAtNode(node, "'declare' keyword is redundant here.");
+				if (ts.isExternalModule(sourceFile)) {
+					ctx.addFailureAtNode(node, "Prefer 'export' to 'declare' in an external module.");
+				} else {
+					// Types do not need 'declare'.
+					switch (node.kind) {
+						case ts.SyntaxKind.InterfaceDeclaration:
+						case ts.SyntaxKind.TypeAliasDeclaration:
+							ctx.addFailureAtNode(node, "'declare' keyword is redundant here.");
+					}
 				}
 			}
 		}
@@ -39,8 +45,7 @@ function walk(ctx: Lint.WalkContext<void>): void {
 		}
 	}
 
-	function checkModule(s: ts.ModuleDeclaration): void {
-		const body = s.body;
+	function checkModule({ body }: ts.ModuleDeclaration): void {
 		if (!body) {
 			return;
 		}

diff --git a/packages/dtslint/src/rules/preferDeclareFunctionRule.ts b/packages/dtslint/src/rules/preferDeclareFunctionRule.ts
@@ -0,0 +1,66 @@
+import * as Lint from "tslint";
+import * as ts from "typescript";
+
+export class Rule extends Lint.Rules.AbstractRule {
+	public static metadata: Lint.IRuleMetadata = {
+		ruleName: "prefer-declare-function",
+		description: "Forbids `export const x = () => void`.",
+		optionsDescription: "Not configurable.",
+		options: null,
+		type: "style",
+		typescriptOnly: true,
+	};
+
+    public static FAILURE_STRING = "Use a function declaration instead of a variable of function type.";
+
+	public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+		return this.applyWithFunction(sourceFile, walk);
+	}
+}
+
+function walk(ctx: Lint.WalkContext<void>): void {
+    eachModuleStatement(ctx.sourceFile, (statement) => {
+        if (isVariableStatement(statement)) {
+            for (const varDecl of statement.declarationList.declarations) {
+                if (varDecl.type !== undefined && varDecl.type.kind === ts.SyntaxKind.FunctionType) {
+                    ctx.addFailureAtNode(varDecl, Rule.FAILURE_STRING);
+                }
+            }
+        }
+    });
+}
+
+function isVariableStatement(node: ts.Node): node is ts.VariableStatement {
+    return node.kind === ts.SyntaxKind.VariableStatement;
+}
+
+function eachModuleStatement(sourceFile: ts.SourceFile, action: (statement: ts.Statement) => void): void{
+	if (!sourceFile.isDeclarationFile) {
+		return;
+	}
+
+	for (const node of sourceFile.statements) {
+		if (isModuleDeclaration(node)) {
+			let { body } = node;
+			if (!body) {
+				return;
+			}
+
+			while (body.kind === ts.SyntaxKind.ModuleDeclaration) {
+				body = body.body;
+			}
+
+			if (body.kind === ts.SyntaxKind.ModuleBlock) {
+				for (const statement of body.statements) {
+					action(statement);
+				}
+			}
+		} else {
+			action(node);
+		}
+	}
+}
+
+function isModuleDeclaration(node: ts.Node): node is ts.ModuleDeclaration {
+	return node.kind === ts.SyntaxKind.ModuleDeclaration;
+}