packages/config: add getOptionalConfig and getOptionalConfigArray to mirror other accessors

packages/config/src/reader.test.ts

@@ -46,10 +46,11 @@ function expectValidValues(config: ConfigReader) {
   expect(config.getStringArray('strings')).toEqual(['string1', 'string2']);
   expect(config.getConfig('nested').getNumber('one')).toBe(1);
   expect(config.getConfig('nested').getString('string')).toBe('string');
-  expect(config.getConfig('nested').getStringArray('strings')).toEqual([
-    'string1',
-    'string2',
-  ]);
+  expect(
+    config.getOptionalConfig('nested')!.getStringArray('strings'),
+  ).toEqual(['string1', 'string2']);
+  expect(config.getOptionalConfig('missing')).toBe(undefined);
+  expect(config.getOptionalConfigArray('missing')).toBe(undefined);
   expect(config.getNumber('zero')).toBe(0);
   expect(config.getBoolean('true')).toBe(true);
   expect(config.getString('string')).toBe('string');
@@ -59,6 +60,9 @@ function expectValidValues(config: ConfigReader) {
   expect(config1.getBoolean('boolean')).toBe(true);
   expect(config2.getString('string')).toBe('string');
   expect(config3.getNumber('number')).toBe(42);
+  expect(
+    config.getOptionalConfigArray('nestlings')![0].getBoolean('boolean'),
+  ).toBe(true);
 }
 
 function expectInvalidValues(config: ConfigReader) {

packages/config/src/reader.ts

@@ -79,8 +79,16 @@ export class ConfigReader implements Config {
   }
 
   getConfig(key: string): ConfigReader {
+    const value = this.getOptionalConfig(key);
+    if (value === undefined) {
+      throw new Error(errors.missing(this.fullKey(key)));
+    }
+    return value;
+  }
+
+  getOptionalConfig(key: string): ConfigReader | undefined {
     const value = this.readValue(key);
-    const fallbackConfig = this.fallback?.getConfig(key);
+    const fallbackConfig = this.fallback?.getOptionalConfig(key);
     const prefix = this.fullKey(key);
 
     if (isObject(value)) {
@@ -91,13 +99,18 @@ export class ConfigReader implements Config {
         errors.type(this.fullKey(key), this.context, typeOf(value), 'object'),
       );
     }
-    return (
-      fallbackConfig ??
-      new ConfigReader(undefined, undefined, undefined, prefix)
-    );
+    return fallbackConfig;
   }
 
   getConfigArray(key: string): ConfigReader[] {
+    const value = this.getOptionalConfigArray(key);
+    if (value === undefined) {
+      throw new Error(errors.missing(this.fullKey(key)));
+    }
+    return value;
+  }
+
+  getOptionalConfigArray(key: string): ConfigReader[] | undefined {
     const configs = this.readConfigValue<JsonObject[]>(key, values => {
       if (!Array.isArray(values)) {
         return { expected: 'object-array' };
@@ -111,7 +124,11 @@ export class ConfigReader implements Config {
       return true;
     });
 
-    return (configs ?? []).map(
+    if (!configs) {
+      return undefined;
+    }
+
+    return configs.map(
       (obj, index) =>
         new ConfigReader(
           obj,

packages/config/src/types.ts

@@ -33,8 +33,10 @@ export type Config = {
   keys(): string[];
 
   getConfig(key: string): Config;
+  getOptionalConfig(key: string): Config | undefined;
 
   getConfigArray(key: string): Config[];
+  getOptionalConfigArray(key: string): Config[] | undefined;
 
   getNumber(key: string): number;
   getOptionalNumber(key: string): number | undefined;