Converted no-single-declare-module from TSLint to ESLint

packages/dtslint/dtslint.json

@@ -9,7 +9,6 @@
         "only-arrow-functions": false,
         // Custom rules
         "expect": true,
-        "no-single-declare-module": true,
         "unified-signatures": true,
         "void-return": true,
         "npm-naming": true,

packages/eslint-plugin/src/rules/index.ts

@@ -15,6 +15,7 @@ import * as noUselessFiles from "./no-useless-files";
 import * as preferDeclareFunction from "./prefer-declare-function";
 import * as redundantUndefined from "./redundant-undefined";
 import * as strictExportDeclareModifiers from "./strict-export-declare-modifiers";
+import * as noSingleDeclareModule from './no-single-declare-module';
 
 export const rules = {
   "dt-header": dtHeader,
@@ -34,4 +35,5 @@ export const rules = {
   "prefer-declare-function": preferDeclareFunction,
   "redundant-undefined": redundantUndefined,
   "strict-export-declare-modifiers": strictExportDeclareModifiers,
+  "no-single-declare-module": noSingleDeclareModule,
 };

packages/eslint-plugin/src/rules/no-single-declare-module.ts

@@ -0,0 +1,58 @@
+import { ESLintUtils } from "@typescript-eslint/utils";
+import * as ts from "typescript";
+
+import { createRule } from "../util";
+
+const rule = createRule({
+  defaultOptions: [],
+  meta: {
+    docs: {
+      description: "Don't use an ambient module declaration if there's just one -- write it as a normal module.",
+      recommended: "error",
+    },
+    messages: {
+      oneModuleDeclaration:
+        "File has only 1 ambient module declaration. Move the contents outside the ambient module block, rename the file to match the ambient module name, and remove the block.",
+    },
+    schema: [],
+    type: "problem",
+  },
+  name: "no-single-declare-module",
+  create(context) {
+    const services = ESLintUtils.getParserServices(context);
+    const sourceFile = services.esTreeNodeToTSNodeMap.get(context.getSourceCode().ast);
+
+    // If it's an external module, any module declarations inside are augmentations.
+    if (ts.isExternalModule(sourceFile)) {
+      return {};
+    }
+
+    let moduleDeclaration: ts.ModuleDeclaration | undefined;
+    for (const statement of sourceFile.statements) {
+      if (ts.isModuleDeclaration(statement) && ts.isStringLiteral(statement.name)) {
+        if (statement.name.text.indexOf("*") !== -1) {
+          // Ignore wildcard module declarations
+          return {};
+        }
+
+        if (moduleDeclaration === undefined) {
+          moduleDeclaration = statement;
+        } else {
+          // Has more than 1 declaration
+          return {};
+        }
+      }
+    }
+
+    if (moduleDeclaration) {
+      context.report({
+        messageId: "oneModuleDeclaration",
+        node: services.tsNodeToESTreeNodeMap.get(moduleDeclaration),
+      });
+    }
+
+    return {};
+  },
+});
+
+export = rule;

packages/eslint-plugin/test/no-single-declare-module.test.ts

@@ -0,0 +1,50 @@
+import { ESLintUtils } from "@typescript-eslint/utils";
+import path from "path";
+
+import rule from "../src/rules/no-single-declare-module";
+
+const ruleTester = new ESLintUtils.RuleTester({
+  parser: "@typescript-eslint/parser",
+  parserOptions: {
+    tsconfigRootDir: __dirname,
+    project: "./tsconfig.no-single-declare-module.json",
+  },
+});
+
+ruleTester.run("no-single-declare-module", rule, {
+  invalid: [
+    {
+      code: `
+        declare module "foo" {}
+
+        // Other global declarations don't affect this. They should go in "declare global".
+        interface I {}
+      `,
+      errors: [
+        {
+          line: 2,
+          messageId: "oneModuleDeclaration",
+        },
+      ],
+    },
+  ],
+  valid: [
+    {
+      code: `
+        import x from "x";
+        declare module "foo" {}
+      `,
+    },
+    {
+      code: `
+        declare module "foo" {}
+        declare module "bar" {}      
+      `,
+    },
+    {
+      code: `
+        declare module "*.svg" {}
+      `,
+    },
+  ],
+});

packages/eslint-plugin/test/tsconfig.no-single-declare-module.json

@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "strict": true,
+    "target": "esnext"
+  },
+  "files": ["file.ts"]
+}