feat: adds $if directive

Author: joelgallant

app-config-default-extensions/index.js

@@ -16,6 +16,7 @@ module.exports = {
     const {
       unescape$Directives,
       tryDirective,
+      ifDirective,
       envDirective,
       extendsDirective,
       extendsSelfDirective,
@@ -31,6 +32,7 @@ module.exports = {
     return [
       unescape$Directives(),
       tryDirective(),
+      ifDirective(),
       v1Compat(),
       envDirective(aliases, environmentOverride, environmentSourceNames),
       extendsDirective(),
@@ -43,18 +45,15 @@ module.exports = {
     ];
   },
   defaultEnvExtensions() {
-    const {
-      unescape$Directives,
-      tryDirective,
-      markAllValuesAsSecret,
-    } = require('@app-config/extensions');
+    const { unescape$Directives, markAllValuesAsSecret } = require('@app-config/extensions');
 
-    return [unescape$Directives(), tryDirective(), markAllValuesAsSecret()];
+    return [unescape$Directives(), markAllValuesAsSecret()];
   },
   defaultMetaExtensions() {
     const {
       unescape$Directives,
       tryDirective,
+      ifDirective,
       extendsDirective,
       extendsSelfDirective,
       overrideDirective,
@@ -63,6 +62,7 @@ module.exports = {
     return [
       unescape$Directives(),
       tryDirective(),
+      ifDirective(),
       extendsDirective(),
       extendsSelfDirective(),
       overrideDirective(),

app-config-extensions/src/index.test.ts

@@ -4,6 +4,7 @@ import { FileSource } from '@app-config/node';
 import { forKey } from '@app-config/extension-utils';
 import {
   tryDirective,
+  ifDirective,
   envDirective,
   extendsDirective,
   extendsSelfDirective,
@@ -94,6 +95,95 @@ describe('$try directive', () => {
   });
 });
 
+describe('$if directive', () => {
+  it('uses main value', async () => {
+    const source = new LiteralSource({
+      $if: {
+        $check: true,
+        $then: 'foobar',
+        $else: 'barfoo',
+      },
+    });
+
+    expect(await source.readToJSON([ifDirective()])).toEqual('foobar');
+  });
+
+  it('uses fallback value', async () => {
+    const source = new LiteralSource({
+      $if: {
+        $check: false,
+        $then: 'foobar',
+        $else: 'barfoo',
+      },
+    });
+
+    expect(await source.readToJSON([ifDirective()])).toEqual('barfoo');
+  });
+
+  it('doesnt evaluate the else branch', async () => {
+    const failDirective = forKey('$fail', () => () => {
+      throw new Error();
+    });
+
+    const source = new LiteralSource({
+      $if: {
+        $check: true,
+        $then: 'barfoo',
+        $else: {
+          $fail: true,
+        },
+      },
+    });
+
+    expect(await source.readToJSON([ifDirective()])).toEqual('barfoo');
+  });
+
+  it('doesnt evaluate the other branch', async () => {
+    const failDirective = forKey('$fail', () => () => {
+      throw new Error();
+    });
+
+    const source = new LiteralSource({
+      $if: {
+        $check: false,
+        $then: {
+          $fail: true,
+        },
+        $else: 'barfoo',
+      },
+    });
+
+    expect(await source.readToJSON([ifDirective()])).toEqual('barfoo');
+  });
+
+  it('disallows missing property', async () => {
+    const source = new LiteralSource({
+      $if: {
+        $check: false,
+        $else: 'barfoo',
+      },
+    });
+
+    await expect(source.readToJSON([ifDirective()])).rejects.toThrow();
+  });
+
+  it('parses $check', async () => {
+    const source = new LiteralSource({
+      $if: {
+        $check: {
+          $env: {
+            default: true,
+          },
+        },
+        $then: 'foobar',
+        $else: 'barfoo',
+      },
+    });
+
+    expect(await source.readToJSON([ifDirective(), envDirective()])).toEqual('foobar');
+  });
+});
+
 describe('$extends directive', () => {
   it('fails if file is missing', async () => {
     const source = new LiteralSource({

app-config-extensions/src/index.ts

@@ -52,7 +52,6 @@ export function tryDirective(): ParsingExtension {
           .addProperty('$fallback', SchemaBuilder.fromJsonSchema({}))
           .addBoolean('$unsafe', {}, false),
       (value) => async (parse) => {
-        // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
         const { $value, $fallback, $unsafe } = value;
 
         try {
@@ -70,6 +69,31 @@ export function tryDirective(): ParsingExtension {
   );
 }
 
+/** Checks a condition, uses then/else */
+export function ifDirective(): ParsingExtension {
+  return forKey(
+    '$if',
+    validateOptions(
+      (SchemaBuilder) =>
+        SchemaBuilder.emptySchema()
+          .addProperty('$check', SchemaBuilder.fromJsonSchema({}))
+          .addProperty('$then', SchemaBuilder.fromJsonSchema({}))
+          .addProperty('$else', SchemaBuilder.fromJsonSchema({})),
+      (value) => async (parse) => {
+        const { $check, $then, $else } = value;
+        const condition = (await parse($check)).toJSON();
+
+        if (condition) {
+          return parse($then, { shouldFlatten: true });
+        } else {
+          return parse($else, { shouldFlatten: true });
+        }
+      },
+      { lazy: true },
+    ),
+  );
+}
+
 /** Uses another file as overriding values, layering them on top of current file */
 export function overrideDirective(): ParsingExtension {
   return fileReferenceDirective('$override', { shouldOverride: true });