Skip linting JSON files entirely (#4001)

This makes TSLint more friendly with the --resolveJsonModule compiler option.

src/linter.ts

@@ -104,13 +104,16 @@ export class Linter {
 
     /**
      * Returns a list of source file names from a TypeScript program. This includes all referenced
-     * files and excludes declaration (".d.ts") files.
+     * files and excludes declaration (".d.ts") files, as well as JSON files, to avoid problems with
+     * `resolveJsonModule`.
      */
     public static getFileNames(program: ts.Program): string[] {
         return mapDefined(
             program.getSourceFiles(),
             file =>
-                file.fileName.endsWith(".d.ts") || program.isSourceFileFromExternalLibrary(file)
+                file.fileName.endsWith(".d.ts") ||
+                file.fileName.endsWith(".json") ||
+                program.isSourceFileFromExternalLibrary(file)
                     ? undefined
                     : file.fileName,
         );

test/executable/executableTests.ts

@@ -19,8 +19,10 @@ import * as cp from "child_process";
 import * as fs from "fs";
 import * as os from "os";
 import * as path from "path";
+import * as semver from "semver";
 import { Logger, Options, run, Status } from "../../src/runner";
 import { denormalizeWinPath } from "../../src/utils";
+import { getNormalizedTypescriptVersion } from "../../src/verify/parse";
 import { createTempFile } from "../utils";
 
 // when tests are run with mocha from npm scripts CWD points to project root
@@ -41,6 +43,8 @@ describe("Executable", function(this: Mocha.ISuiteCallbackContext) {
     this.slow(3000); // the executable is JIT-ed each time it runs; avoid showing slowness warnings
     this.timeout(10000);
 
+    const tsVersion = getNormalizedTypescriptVersion();
+
     describe("Files", () => {
         it("exits with code 1 if no arguments passed", done => {
             execCli([], (err, stdout, stderr) => {
@@ -596,6 +600,13 @@ describe("Executable", function(this: Mocha.ISuiteCallbackContext) {
                 fs.readFileSync("test/files/project-multiple-fixes/after.test.ts", "utf-8"),
             );
         }).timeout(8000);
+
+        if (semver.satisfies(tsVersion, ">=2.9")) {
+            it("does not try to parse JSON files with --resolveJsonModule with TS >= 2.9", async () => {
+                const status = await execRunner({project: "test/files/tsconfig-resolve-json-module/tsconfig.json"});
+                assert.equal(status, Status.Ok, "process should exit without an error");
+            });
+        }
     });
 
     describe("--type-check", () => {

test/files/tsconfig-resolve-json-module/index.ts

@@ -0,0 +1,3 @@
+import settings from "./test.json";
+// tslint:disable-next-line:no-console
+console.log(settings.dry);

test/files/tsconfig-resolve-json-module/test.json

@@ -0,0 +1,4 @@
+{
+  "dry": false,
+  "debug": false
+}

test/files/tsconfig-resolve-json-module/tsconfig.json

@@ -0,0 +1,8 @@
+{
+    "include": ["index.ts"],
+    "compilerOptions": {
+      "resolveJsonModule": true,
+      "allowSyntheticDefaultImports": true,
+      "esModuleInterop": true
+    }
+}

test/files/tsconfig-resolve-json-module/tslint.json

@@ -0,0 +1,5 @@
+{
+    "extends": [
+        "tslint:latest"
+    ]
+}