fix: parsing tree extensions with composeExtensions

Author: joelgallant

app-config-extension-utils/src/index.ts

@@ -7,11 +7,22 @@ import { parseValue, Root, AppConfigError } from '@app-config/core';
 import { SchemaBuilder } from '@serafin/schema-builder';
 
 export function composeExtensions(extensions: ParsingExtension[]): ParsingExtension {
-  return (value, [k]) => {
+  const composed: ParsingExtension = (value, [k]) => {
+    // only applies to the root - override the parsing extensions
     if (k !== Root) return false;
 
-    return (_, __, source) => parseValue(value, source, extensions, { shouldFlatten: true });
+    return (_, __, source, baseExtensions) =>
+      // restart the parse tree, but with additional extensions included
+      parseValue(
+        value,
+        source,
+        // ensures that a recursion doesn't happen
+        baseExtensions.concat(extensions).filter((v) => v !== composed),
+        { shouldFlatten: true },
+      );
   };
+
+  return composed;
 }
 
 export function named(name: string, parsingExtension: ParsingExtension): ParsingExtension {

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

@@ -7,6 +7,8 @@ import {
   envDirective,
   extendsDirective,
   substituteDirective,
+  envVarDirective,
+  parseDirective,
 } from './index';
 
 /* eslint-disable no-template-curly-in-string */
@@ -121,4 +123,34 @@ describe('extension combinations', () => {
 
     await expect(source.readToJSON([ifDirective(), eqDirective()])).resolves.toEqual('foo');
   });
+
+  it('combines $envVar and $parseBool directives', async () => {
+    process.env.FOO = '1';
+
+    const source = new LiteralSource({
+      featureEnabled: {
+        $parseBool: {
+          $envVar: 'FOO',
+        },
+      },
+    });
+
+    const parsed = await source.read([envVarDirective(), parseDirective()]);
+
+    expect(parsed.toJSON()).toEqual({ featureEnabled: true });
+  });
+
+  it('combines $envVar and $parseBool directives 2', async () => {
+    const source = new LiteralSource({
+      featureEnabled: {
+        $parseBool: {
+          $envVar: { name: 'FOO', allowNull: true, fallback: null },
+        },
+      },
+    });
+
+    const parsed = await source.read([parseDirective(), envVarDirective()]);
+
+    expect(parsed.toJSON()).toEqual({ featureEnabled: false });
+  });
 });