Test: TS type specification strength tests (PoC)

package.json

@@ -48,6 +48,7 @@
     "test:ui:runner": "node scripts/functional_test_runner",
     "test:server": "grunt test:server",
     "test:coverage": "grunt test:coverage",
+    "typespec": "typings-tester --config x-pack/plugins/canvas/public/lib/aeroelastic/tsconfig.json x-pack/plugins/canvas/public/lib/aeroelastic/__tests__/typescript/typespec_tests.ts",
     "checkLicenses": "grunt licenses --dev",
     "build": "node scripts/build --all-platforms",
     "start": "node --trace-warnings --trace-deprecation scripts/kibana --dev ",
@@ -407,6 +408,7 @@
     "tslint-microsoft-contrib": "^6.0.0",
     "tslint-plugin-prettier": "^2.0.0",
     "typescript": "^3.0.3",
+    "typings-tester": "^0.3.2",
     "vinyl-fs": "^3.0.2",
     "xml2js": "^0.4.19",
     "xmlbuilder": "9.0.4",

x-pack/plugins/canvas/public/lib/aeroelastic/__tests__/typescript/typespec_tests.ts

@@ -0,0 +1,80 @@
+import { select } from '../../select';
+import { Json, Selector } from '../..';
+
+/*
+
+  Type checking isn't too useful if future commits can accidentally weaken the type constraints, because a
+  TypeScript linter will not complain - everything that passed before will continue to pass. The coder
+  will not have feedback that the original intent with the typing got compromised. To declare the intent
+  via passing and failing type checks, test cases are needed, some of which designed to expect a TS pass,
+  some of them to expect a TS complaint. It documents intent for peers too, as type specs are a tough read.
+
+  Run compile-time type specification tests in the `kibana` root with:
+
+     yarn typespec
+
+  Test "cases" expecting to pass TS checks are not annotated, while ones we want TS to complain about
+  are prepended with the comment
+ 
+  // typings:expect-error
+
+  The test "suite" and "cases" are wrapped in IIFEs to prevent linters from complaining about the unused
+  binding. It can be structured internally as desired.
+  
+*/
+
+((): void => {
+  /**
+   * TYPE TEST SUITE
+   */
+
+  (function jsonTests(plain: Json): void {
+    // numbers are OK
+    plain = 1;
+    plain = NaN;
+    plain = Infinity;
+    plain = -Infinity;
+    plain = Math.pow(2, 6);
+    // other JSON primitive types are OK
+    plain = false;
+    plain = 'hello';
+    plain = null;
+    // structures made of above and of structures are OK
+    plain = {};
+    plain = [];
+    plain = { a: 1 };
+    plain = [0, null, false, NaN, 3.14, 'one more'];
+    plain = { a: { b: 5, c: { d: [1, 'a', -Infinity, null], e: -1 }, f: 'b' }, g: false };
+
+    // typings:expect-error
+    plain = undefined; // it's undefined
+    // typings:expect-error
+    plain = a => a; // it's a function
+    // typings:expect-error
+    plain = [new Date()]; // it's a time
+    // typings:expect-error
+    plain = { a: Symbol('haha') }; // symbol isn't permitted either
+    // typings:expect-error
+    plain = window || void 0;
+    // typings:expect-error
+    plain = { a: { b: 5, c: { d: [1, 'a', undefined, null] } } }; // going deep into the structure
+
+    return; // jsonTests
+  })(null);
+
+  (function selectTests(selector: Selector): void {
+    select((a: Json) => a); // one arg
+    select((a: Json, b: Json): Json => `${a} and ${b}`); // more args
+    select(() => 1); // zero arg
+    select((...args: Json[]) => args); // variadic
+
+    // typings:expect-error
+    select(() => {}); // should yield a JSON value, but it returns void
+    // typings:expect-error
+    select((x: Json) => ({ a: x, b: undefined })); // should return a Json
+
+    return; // selectTests
+  })(select((a: Json) => a));
+
+  return; // test suite
+})();

x-pack/plugins/canvas/public/lib/aeroelastic/tsconfig.json

@@ -0,0 +1,19 @@
+{
+  "extends": "../../../../../tsconfig",
+  "compilerOptions": {
+    "module": "commonjs",
+    "lib": ["esnext", "dom"],
+    "noImplicitAny": true,
+    "strictNullChecks": true,
+    "strictFunctionTypes": false,
+    "strictPropertyInitialization": true,
+    "noImplicitThis": true,
+    "noImplicitReturns": true,
+    "forceConsistentCasingInFileNames": false,
+    "noEmit": true,
+    "baseUrl": ".",
+    "paths": {
+      "layout/*": ["aeroelastic/*"]
+    }
+  }
+}

x-pack/tsconfig.json

@@ -9,7 +9,8 @@
     "typings/**/*"
   ],
   "exclude": [
-    "test/**/*"
+    "test/**/*",
+    "**/typespec_tests.ts"
   ],
   "compilerOptions": {
     "paths": {

yarn.lock

@@ -5740,7 +5740,7 @@ [email protected]:
   resolved "https://registry.yarnpkg.com/commander/-/commander-0.6.1.tgz#fa68a14f6a945d54dbbe50d8cdb3320e9e3b1a06"
   integrity sha1-+mihT2qUXVTbvlDYzbMyDp47GgY=
 
-commander@2, [email protected], commander@^2.11.0, commander@^2.12.1, commander@^2.8.1, commander@^2.9.0:
+commander@2, [email protected], commander@^2.11.0, commander@^2.12.1, commander@^2.12.2, commander@^2.8.1, commander@^2.9.0:
   version "2.19.0"
   resolved "https://registry.yarnpkg.com/commander/-/commander-2.19.0.tgz#f6198aa84e5b83c46054b94ddedbfed5ee9ff12a"
   integrity sha512-6tvAOO+D6OENvRAh524Dh9jcfKTYDQAqvqezbCW82xj5X0pSrcpxtvRKHLG0yBY6SD7PSDrJaj+0AiOcKVd1Xg==
@@ -21723,6 +21723,13 @@ typescript@^3.0.3:
   resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.0.3.tgz#4853b3e275ecdaa27f78fda46dc273a7eb7fc1c8"
   integrity sha512-kk80vLW9iGtjMnIv11qyxLqZm20UklzuR2tL0QAnDIygIUIemcZMxlMWudl9OOt76H3ntVzcTiddQ1/pAAJMYg==
 
+typings-tester@^0.3.2:
+  version "0.3.2"
+  resolved "https://registry.yarnpkg.com/typings-tester/-/typings-tester-0.3.2.tgz#04cc499d15ab1d8b2d14dd48415a13d01333bc5b"
+  integrity sha512-HjGoAM2UoGhmSKKy23TYEKkxlphdJFdix5VvqWFLzH1BJVnnwG38tpC6SXPgqhfFGfHY77RlN1K8ts0dbWBQ7A==
+  dependencies:
+    commander "^2.12.2"
+
 ua-parser-js@^0.7.18, ua-parser-js@^0.7.9:
   version "0.7.18"
   resolved "https://registry.yarnpkg.com/ua-parser-js/-/ua-parser-js-0.7.18.tgz#a7bfd92f56edfb117083b69e31d2aa8882d4b1ed"