feat: formatting JSON output

closes llvm#43

package.json

@@ -95,6 +95,17 @@
               "trace"
             ],
             "default": "info"
+          },
+          "parquet-viewer.jsonSpace": {
+            "markdownDescription": "JSON indentation space, passed to `JSON.stringify` as is, see [mdn](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#parameters) for details. Only applies when `#parquet-viewer.useParquetTools#` is `false`.",
+            "type": [
+              "string",
+              "number"
+            ],
+            "default": 0,
+            "minimum": 0,
+            "maximum": 10,
+            "maxLength": 10
           }
         }
       }

src/parquets-backend.ts

@@ -3,6 +3,7 @@ import { getLogger } from './logger';
 import { ParquetReader } from '@dvirtz/parquets';
 import * as os from 'os';
 import { ParquetBackend } from './parquet-backend';
+import { jsonSpace } from './settings';
 
 export class ParquetsBackend implements ParquetBackend {
   public async * toJson(parquetPath: string, token?: vscode.CancellationToken): AsyncGenerator<string> {
@@ -20,7 +21,7 @@ export class ParquetsBackend implements ParquetBackend {
       // read all records from the file and print them
       let record = null;
       while (!token?.isCancellationRequested && (record = await cursor.next())) {
-        yield `${JSON.stringify(record)}${os.EOL}`;
+        yield `${JSON.stringify(record, null, jsonSpace())}${os.EOL}`;
       }
 
       await reader.close();

src/settings.ts

@@ -40,3 +40,7 @@ export async function setLogLevel(logLevel: LogLevel | undefined): Promise<void>
 export function useParquetTools(): boolean {
   return settings().get('useParquetTools', false);
 }
+
+export function jsonSpace(): number | string | undefined {
+  return settings().get('jsonSpace');
+}

test/unit/parquets-backend.test.ts

@@ -4,6 +4,7 @@ import { createReadStream } from 'fs';
 import * as path from 'path';
 import { createInterface } from 'readline';
 import { ParquetsBackend } from '../../src/parquets-backend';
+import { jsonSpace } from '../../src/settings';
 
 
 const rootDir = path.join(__dirname, '..', '..');
@@ -20,13 +21,15 @@ jest.mock('vscode', () => {
   };
 });
 
+jest.mock('../../src/settings');
+
 describe("ParquetsBackend tests", () => {
   const backend = new ParquetsBackend();
+  const workspace = path.join(rootDir, 'test', 'workspace');
 
   test.each(
     ["small", "large"]
   )('Converts %s parquet to JSON', async function (name) {
-    const workspace = path.join(rootDir, 'test', 'workspace');
     const json = (await toArray(backend.toJson(path.join(workspace, `${name}.parquet`)))).map(line => line.trim());
     const expected = await toArray(createInterface({input: createReadStream(path.join(workspace, `${name}.json`))}));
 
@@ -38,4 +41,14 @@ describe("ParquetsBackend tests", () => {
       'message': expect.stringMatching(/while reading no-such-file: Error: ENOENT: no such file or directory, stat '.*no-such-file'/)
     });
   });
+
+  test.each([0, 2, 10, "\t", "###"])('Test space %s', async function (space) {
+    jest.mocked(jsonSpace).mockReturnValue(space);
+
+    const json = (await toArray(backend.toJson(path.join(workspace, `small.parquet`)))).map(line => line.trim());
+    const records = await toArray(createInterface({input: createReadStream(path.join(workspace, `small.json`))}));
+    const expected = records.map(record => JSON.stringify(JSON.parse(record), null, space));
+
+    expect(json).toEqual(expected);
+  });
 });