Suggest language when one isn't found

package.json

@@ -46,6 +46,7 @@
   },
   "devDependencies": {
     "@types/cosmiconfig": "5.0.3",
+    "@types/fast-levenshtein": "0.0.1",
     "@types/jest": "23.3.9",
     "@types/yargs": "12.0.1",
     "@unibeautify/beautifier-eslint": "0.6.0",
@@ -61,6 +62,7 @@
   "dependencies": {
     "chalk": "^2.4.1",
     "cosmiconfig": "^5.0.6",
+    "fast-levenshtein": "^2.0.6",
     "g-search": "^0.3.0",
     "requireg": "^0.2.1",
     "unibeautify": "^0.17.0",

src/commands/BeautifyCommand.ts

@@ -1,8 +1,9 @@
-import { BeautifyData } from "unibeautify";
+import { BeautifyData, Unibeautify } from "unibeautify";
 import cosmiconfig from "cosmiconfig";
 import * as fs from "fs";
+import * as levenshtein from "fast-levenshtein";
 
-import { setupUnibeautify } from "../utils";
+import { setupUnibeautify, getAllLanguages } from "../utils";
 import { BaseCommand } from "./BaseCommand";
 
 export class BeautifyCommand extends BaseCommand {
@@ -11,30 +12,28 @@ export class BeautifyCommand extends BaseCommand {
   public beautify(programArgs: IArgs): Promise<string> {
     const { language, filePath } = programArgs;
     return setupUnibeautify().then(unibeautify => {
-      if (!language) {
-        const error = new Error("A language is required.");
-        return this.handleError(error, 1);
-      }
-      return Promise.all([
-        this.readConfig(programArgs),
-        this.readText(filePath),
-      ]).then(([config, text]) => {
-        const data: BeautifyData = {
-          filePath: filePath,
-          languageName: language,
-          options: (config as any) || {},
-          text,
-        };
-        return unibeautify
-          .beautify(data)
-          .then((result: string) => {
-            return this.writeToFileOrStdout({ result, programArgs }).then(
-              () => result
-            );
-          })
-          .catch((error: Error) => {
-            return this.handleError(error, 1);
-          });
+      return this.validateLanguage(language, unibeautify).then(() => {
+        return Promise.all([
+          this.readConfig(programArgs),
+          this.readText(filePath),
+        ]).then(([config, text]) => {
+          const data: BeautifyData = {
+            filePath: filePath,
+            languageName: language,
+            options: (config as any) || {},
+            text,
+          };
+          return unibeautify
+            .beautify(data)
+            .then((result: string) => {
+              return this.writeToFileOrStdout({ result, programArgs }).then(
+                () => result
+              );
+            })
+            .catch((error: Error) => {
+              return this.handleError(error, 1);
+            });
+        });
       });
     });
   }
@@ -143,6 +142,40 @@ export class BeautifyCommand extends BaseCommand {
       });
     });
   }
+
+  private validateLanguage(
+    language: string | undefined,
+    unibeautify: Unibeautify
+  ): Promise<void> {
+    if (!language) {
+      const error = new Error("A language is required.");
+      return this.handleError(error, 1);
+    }
+    const langs = unibeautify.findLanguages({ name: language });
+    if (langs.length === 0) {
+      const allLanguages = getAllLanguages();
+      const distances: number[] = allLanguages.map(lang =>
+        levenshtein.get(lang.toLowerCase(), language.toLowerCase())
+      );
+      const bestDistance: number = Math.min(...distances);
+      const distanceThreshold = 2;
+      const bestMatchLanguages = allLanguages.filter(
+        (lang, index) =>
+          distances[index] <= Math.min(distanceThreshold, bestDistance)
+      );
+      if (bestMatchLanguages.length > 0) {
+        const limit = 3;
+        const error = new Error(
+          `Language '${language}' was not found. Did you mean:\n${bestMatchLanguages
+            .slice(0, limit)
+            .map(lang => `  - ${lang}`)
+            .join("\n")}`
+        );
+        return this.handleError(error, 1);
+      }
+    }
+    return Promise.resolve();
+  }
 }
 
 /**

test/commands/BeautifyCommand.spec.ts

@@ -214,7 +214,7 @@ describe("BeautifyCommand", () => {
           args: [],
           configFile: "test/.unibeautifyrc.yml",
           filePath: "test/fixtures/test1.js",
-          language: "javascript",
+          language: "thisIsntALanguage",
         })
         .then(thenCb)
         .catch(catchCb)
@@ -232,6 +232,60 @@ describe("BeautifyCommand", () => {
           expect(json).toMatchSnapshot("json");
         });
     });
+    test("should throw an error suggesting JavaScript for language", () => {
+      const command = new CustomCommand();
+      const thenCb = jest.fn();
+      const catchCb = jest.fn();
+      return command
+        .beautify({
+          args: [],
+          configFile: "test/.unibeautifyrc.yml",
+          filePath: "test/fixtures/test1.js",
+          language: "javascript",
+        })
+        .then(thenCb)
+        .catch(catchCb)
+        .then(() => {
+          expect(thenCb).not.toBeCalled();
+          expect(catchCb).toHaveBeenCalled();
+          expect(catchCb.mock.calls).toHaveLength(1);
+          expect(catchCb.mock.calls[0]).toHaveLength(1);
+          expect(catchCb).toHaveProperty(
+            ["mock", "calls", 0, 0, "message"],
+            "Language 'javascript' was not found. Did you mean:\n  - JavaScript"
+          );
+          const json = command.toJSON();
+          expect(json.exitCode).toBe(1);
+          expect(json).toMatchSnapshot("json");
+        });
+    });
+    test("should throw an error suggesting C, D and E for language", () => {
+      const command = new CustomCommand();
+      const thenCb = jest.fn();
+      const catchCb = jest.fn();
+      return command
+        .beautify({
+          args: [],
+          configFile: "test/.unibeautifyrc.yml",
+          filePath: "test/fixtures/test1.js",
+          language: "a",
+        })
+        .then(thenCb)
+        .catch(catchCb)
+        .then(() => {
+          expect(thenCb).not.toBeCalled();
+          expect(catchCb).toHaveBeenCalled();
+          expect(catchCb.mock.calls).toHaveLength(1);
+          expect(catchCb.mock.calls[0]).toHaveLength(1);
+          expect(catchCb).toHaveProperty(
+            ["mock", "calls", 0, 0, "message"],
+            "Language 'a' was not found. Did you mean:\n  - C\n  - D\n  - E"
+          );
+          const json = command.toJSON();
+          expect(json.exitCode).toBe(1);
+          expect(json).toMatchSnapshot("json");
+        });
+    });
     test("should throw an error with invalid json", () => {
       const command = new CustomCommand();
       const thenCb = jest.fn();

test/commands/__snapshots__/BeautifyCommand.spec.ts.snap

@@ -48,6 +48,28 @@ Object {
 }
 `;
 
+exports[`BeautifyCommand Errors should throw an error suggesting C, D and E for language: json 1`] = `
+Object {
+  "exitCode": 1,
+  "stderr": "Language 'a' was not found. Did you mean:
+  - C
+  - D
+  - E
+",
+  "stdout": "",
+}
+`;
+
+exports[`BeautifyCommand Errors should throw an error suggesting JavaScript for language: json 1`] = `
+Object {
+  "exitCode": 1,
+  "stderr": "Language 'javascript' was not found. Did you mean:
+  - JavaScript
+",
+  "stdout": "",
+}
+`;
+
 exports[`BeautifyCommand Errors should throw an error with invalid json: json 1`] = `
 Object {
   "exitCode": 2,