Fix an issue where module resolution didn't follow symlinks. (palanti…

…r#4295)

* Fix an issue where module resolution didn't follow symlinks.

* Fix several lint issues.

* Fix some style issues.

src/configuration.ts

@@ -20,12 +20,11 @@ import * as yaml from "js-yaml";
 import { Minimatch } from "minimatch";
 import * as os from "os";
 import * as path from "path";
-import * as resolve from "resolve";
 import { FatalError, showWarningOnce } from "./error";
 
 import { IOptions, RuleSeverity } from "./language/rule/rule";
 import { findRule } from "./ruleLoader";
-import { arrayify, hasOwnProperty, stripComments } from "./utils";
+import { arrayify, hasOwnProperty, stripComments, tryResolvePackage } from "./utils";
 
 export interface IConfigurationFile {
     /**
@@ -309,17 +308,18 @@ function resolveConfigurationPath(filePath: string, relativeTo?: string) {
 
     const basedir = relativeTo !== undefined ? relativeTo : process.cwd();
     try {
-        return resolve.sync(filePath, { basedir });
-    } catch (err) {
-        try {
-            return require.resolve(filePath);
-        } catch (err) {
-            throw new Error(
-                `Invalid "extends" configuration value - could not require "${filePath}". ` +
-                    "Review the Node lookup algorithm (https://nodejs.org/api/modules.html#modules_all_together) " +
-                    "for the approximate method TSLint uses to find the referenced configuration file.",
-            );
+        let resolvedPackagePath: string | undefined = tryResolvePackage(filePath, basedir);
+        if (resolvedPackagePath === undefined) {
+            resolvedPackagePath = require.resolve(filePath);
         }
+
+        return resolvedPackagePath;
+    } catch (err) {
+        throw new Error(
+            `Invalid "extends" configuration value - could not require "${filePath}". ` +
+                "Review the Node lookup algorithm (https://nodejs.org/api/modules.html#modules_all_together) " +
+                "for the approximate method TSLint uses to find the referenced configuration file.",
+        );
     }
 }
 
@@ -411,10 +411,9 @@ export function getRulesDirectories(
 ): string[] {
     return arrayify(directories).map(dir => {
         if (!useAsPath(dir)) {
-            try {
-                return path.dirname(resolve.sync(dir, { basedir: relativeTo }));
-            } catch (err) {
-                // swallow error and fallback to using directory as path
+            const resolvedPackagePath: string | undefined = tryResolvePackage(dir, relativeTo);
+            if (resolvedPackagePath !== undefined) {
+                return path.dirname(resolvedPackagePath);
             }
         }
 

src/formatterLoader.ts

@@ -17,9 +17,8 @@
 
 import * as fs from "fs";
 import * as path from "path";
-import * as resolve from "resolve";
 import { FormatterConstructor } from "./index";
-import { camelize } from "./utils";
+import { camelize, tryResolvePackage } from "./utils";
 
 const CORE_FORMATTERS_DIRECTORY = path.resolve(__dirname, "formatters");
 
@@ -79,17 +78,17 @@ function loadFormatter(
 }
 
 function loadFormatterModule(name: string): FormatterConstructor | undefined {
-    let src: string;
+    let src: string | undefined;
     try {
         // first try to find a module in the dependencies of the currently linted project
-        src = resolve.sync(name, { basedir: process.cwd() });
-    } catch {
-        try {
+        src = tryResolvePackage(name, process.cwd());
+        if (src === undefined) {
             // if there is no local module, try relative to the installation of TSLint (might be global)
             src = require.resolve(name);
-        } catch {
-            return undefined;
         }
+    } catch {
+        return undefined;
     }
+
     return (require(src) as { Formatter: FormatterConstructor }).Formatter;
 }

src/utils.ts

@@ -15,6 +15,9 @@
  * limitations under the License.
  */
 
+import * as fs from "fs";
+import * as resolve from "resolve";
+
 /**
  * Enforces the invariant that the input is an array.
  */
@@ -261,3 +264,31 @@ export function isKebabCased(name: string): boolean {
 export function isSnakeCased(name: string): boolean {
     return isSeparatorCased(name, "-");
 }
+
+/**
+ * Tries to resolve a package by name, optionally relative to a file path. If the
+ * file path is under a symlink, it tries to resolve the package under both the real path and under
+ * the symlink path.
+ */
+export function tryResolvePackage(packageName: string, relativeTo?: string): string | undefined {
+    const realRelativeToPath: string | undefined =
+        relativeTo !== undefined ? fs.realpathSync(relativeTo) : undefined;
+
+    let resolvedPath: string | undefined = tryResolveSync(packageName, realRelativeToPath);
+    if (resolvedPath === undefined) {
+        resolvedPath = tryResolveSync(packageName, relativeTo);
+    }
+
+    return resolvedPath;
+}
+
+/**
+ * Calls `resolve.sync` and if it fails, it returns `undefined`
+ */
+function tryResolveSync(packageName: string, relativeTo?: string): string | undefined {
+    try {
+        return resolve.sync(packageName, { basedir: relativeTo });
+    } catch {
+        return undefined;
+    }
+}