feat: implement getFirstPrimitiveProperty (#34)

* feat: implement getFirstPrimitiveProperty

* fix: moar errors

Author: P0lip

package.json

@@ -33,7 +33,7 @@
     "release": "sl-scripts release",
     "release.dryRun": "sl-scripts release --dry-run --debug",
     "test": "jest",
-    "test.prod": "yarn lint && yarn test --coverage --no-cache",
+    "test.prod": "yarn lint && yarn test --coverage --no-cache --max-workers=2",
     "test.update": "yarn test --updateSnapshot",
     "test.watch": "yarn test --watch"
   },

src/__tests__/getFirstPrimitiveProperty.ts

@@ -0,0 +1,25 @@
+import { getFirstPrimitiveProperty } from '../getFirstPrimitiveProperty';
+
+describe('getFirstPrimitiveProperty', () => {
+  it.each(['true', 'null', '[]', '{}', '{"a":[]}', '{"a":{}}'])(
+    'returns nothing when no valid property is found %s',
+    text => {
+      expect(getFirstPrimitiveProperty(text)).toBeUndefined();
+    },
+  );
+
+  it.each(['{', '{2', '{"d', '{"dd"dd', '{"dd":', '{"d": fa'])('throws SyntaxError given %s', text => {
+    expect(getFirstPrimitiveProperty.bind(null, text)).toThrow(SyntaxError);
+  });
+
+  it('gets first primitive property', () => {
+    expect(getFirstPrimitiveProperty(`{"swagger":"2.0","test":true}`)).toEqual(['swagger', '2.0']);
+    expect(getFirstPrimitiveProperty(`{"swagger":2,"baz": {}}`)).toEqual(['swagger', 2]);
+    expect(getFirstPrimitiveProperty(`{"swagger":true}`)).toEqual(['swagger', true]);
+    expect(getFirstPrimitiveProperty(`{"swagger":false}`)).toEqual(['swagger', false]);
+    expect(getFirstPrimitiveProperty(`{"swagger":null}`)).toEqual(['swagger', null]);
+    expect(getFirstPrimitiveProperty(`{"openapi":"3.0"}`)).toEqual(['openapi', '3.0']);
+    expect(getFirstPrimitiveProperty(`{"openapi":3.1}`)).toEqual(['openapi', 3.1]);
+    expect(getFirstPrimitiveProperty(`{"openapi":3.1,"test":"foo"`)).toEqual(['openapi', 3.1]);
+  });
+});

src/getFirstPrimitiveProperty.ts

@@ -0,0 +1,50 @@
+import { Optional } from '@stoplight/types';
+import { createScanner, SyntaxKind } from 'jsonc-parser';
+
+export const getFirstPrimitiveProperty = (text: string): Optional<[string, string | number | boolean | null]> => {
+  const scanner = createScanner(text, true);
+
+  scanner.scan();
+
+  if (scanner.getToken() !== SyntaxKind.OpenBraceToken) {
+    return;
+  }
+
+  scanner.scan();
+
+  if (scanner.getToken() === SyntaxKind.CloseBraceToken) {
+    return;
+  }
+
+  if (scanner.getToken() !== SyntaxKind.StringLiteral) {
+    throw new SyntaxError('Unexpected character');
+  }
+
+  const property = scanner.getTokenValue();
+  scanner.scan();
+
+  if (scanner.getToken() !== SyntaxKind.ColonToken) {
+    throw new SyntaxError('Colon expected');
+  }
+
+  scanner.scan();
+
+  switch (scanner.getToken()) {
+    case SyntaxKind.StringLiteral:
+      return [property, scanner.getTokenValue()];
+    case SyntaxKind.NumericLiteral:
+      return [property, Number(scanner.getTokenValue())]; // note we should validate the number, but let's have a loose check
+    case SyntaxKind.TrueKeyword:
+      return [property, true];
+    case SyntaxKind.FalseKeyword:
+      return [property, false];
+    case SyntaxKind.NullKeyword:
+      return [property, null];
+    case SyntaxKind.Unknown:
+      throw new SyntaxError('Unexpected character');
+    case SyntaxKind.EOF:
+      throw new SyntaxError('Unexpected end of file');
+    default:
+      return;
+  }
+};

src/index.ts

@@ -2,6 +2,7 @@ export * from './decodePointer';
 export * from './decodePointerFragment';
 export * from './encodePointer';
 export * from './encodePointerFragment';
+export * from './getFirstPrimitiveProperty';
 export * from './getJsonPathForPosition';
 export * from './getLastPathSegment';
 export * from './getLocationForJsonPath';