feat: add ability to specify config file search path (#48)

README.md

@@ -82,6 +82,17 @@ If there is no option provided, it'll try to load [config file](https://github.c
 }
 ```
 
+If you'd like to specify where to find the config file, just put the search path (relative to `process.cwd()`) in the second argument, the following example shows how to use the config file from `<cwd>/configs/.prettierrc`:
+
+```json
+{
+  "extends": ["tslint-plugin-prettier"],
+  "rules": {
+    "prettier": [true, "configs"]
+  }
+}
+```
+
 If you'd like to specify options manually, just put [Prettier Options](https://github.com/prettier/prettier#options) in the second argument, for example:
 
 ```json

fixtures/no-semi/.prettierrc

@@ -0,0 +1,3 @@
+{
+  "semi": false
+}

src/prettierRule.ts

@@ -1,5 +1,6 @@
 import assert = require('assert');
 import * as utils from 'eslint-plugin-prettier';
+import * as path from 'path';
 import * as prettier from 'prettier';
 import * as tslint from 'tslint';
 import * as ts from 'typescript';
@@ -24,10 +25,33 @@ class Walker extends tslint.AbstractWalker<any[]> {
       case 'object':
         options = rule_argument_1 as prettier.Options;
         break;
-      default:
+      case 'string': {
         try {
-          // tslint:disable-next-line:strict-type-predicates
-          assert(typeof prettier.resolveConfig.sync === 'function');
+          assert_existence_of_resolve_config_sync();
+        } catch {
+          // istanbul ignore next
+          throw new Error(
+            `Require [email protected]+ to specify config file, but got prettier@${prettier.version}.`,
+          );
+        }
+
+        const file_path = path.resolve(
+          process.cwd(),
+          rule_argument_1 as string,
+        );
+        const resolved_config = prettier.resolveConfig.sync(file_path);
+
+        // istanbul ignore next
+        if (resolved_config === null) {
+          throw new Error(`Config file not found: ${file_path}`);
+        }
+
+        options = resolved_config;
+        break;
+      }
+      default: {
+        try {
+          assert_existence_of_resolve_config_sync();
         } catch {
           // backward compatibility: use default options if no resolveConfig.sync()
           // istanbul ignore next
@@ -37,10 +61,13 @@ class Walker extends tslint.AbstractWalker<any[]> {
         const resolved_config = prettier.resolveConfig.sync(
           source_file.fileName,
         );
+
         if (resolved_config !== null) {
           options = resolved_config;
         }
+
         break;
+      }
     }
 
     const source = source_file.getFullText();
@@ -97,3 +124,8 @@ class Walker extends tslint.AbstractWalker<any[]> {
     });
   }
 }
+
+function assert_existence_of_resolve_config_sync() {
+  // tslint:disable-next-line:strict-type-predicates
+  assert(typeof prettier.resolveConfig.sync === 'function');
+}

tests/prettier/specified-config/no-semi.ts.fix

@@ -0,0 +1 @@
+const x = "there should be no semi at the end of this line"

tests/prettier/specified-config/no-semi.ts.lint

@@ -0,0 +1,2 @@
+const x = "there should be no semi at the end of this line";
+                                                           ~ [Delete `;`]

tests/prettier/specified-config/tslint.json

@@ -0,0 +1,6 @@
+{
+  "rulesDirectory": ["../../../rules"],
+  "rules": {
+    "prettier": [true, "./fixtures/no-semi"]
+  }
+}