feat: adds 'allowMissing' option on $envVar

Author: joelgallant

app-config-extensions/src/env-var-directive.test.ts

@@ -22,7 +22,7 @@ describe('$envVar directive', () => {
     expect(parsed.toJSON()).toEqual({ foo: 'foo', bar: 'bar' });
   });
 
-  it('reads object with $name', async () => {
+  it('reads object with name', async () => {
     process.env.FOO = 'foo';
 
     const source = new LiteralSource({
@@ -34,15 +34,15 @@ describe('$envVar directive', () => {
     expect(parsed.toJSON()).toEqual({ foo: 'foo' });
   });
 
-  it('fails with $name when not defined', async () => {
+  it('fails with name when not defined', async () => {
     const source = new LiteralSource({
       foo: { $envVar: { name: 'FOO' } },
     });
 
     await expect(source.read([envVarDirective()])).rejects.toThrow();
   });
 
-  it('uses $name when $fallback is defined', async () => {
+  it('uses name when fallback is defined', async () => {
     process.env.FOO = 'foo';
 
     const source = new LiteralSource({
@@ -54,7 +54,7 @@ describe('$envVar directive', () => {
     expect(parsed.toJSON()).toEqual({ foo: 'foo' });
   });
 
-  it('uses $fallback when $name was not found', async () => {
+  it('uses fallback when name was not found', async () => {
     const source = new LiteralSource({
       foo: { $envVar: { name: 'FOO', fallback: 'bar' } },
     });
@@ -64,7 +64,7 @@ describe('$envVar directive', () => {
     expect(parsed.toJSON()).toEqual({ foo: 'bar' });
   });
 
-  it('allows null value when $allowNull', async () => {
+  it('allows null value when allowNull', async () => {
     const source = new LiteralSource({
       foo: { $envVar: { name: 'FOO', fallback: null, allowNull: true } },
     });
@@ -74,14 +74,27 @@ describe('$envVar directive', () => {
     expect(parsed.toJSON()).toEqual({ foo: null });
   });
 
-  it('does not allow number even when $allowNull', async () => {
+  it('does not allow number even when allowNull', async () => {
     const source = new LiteralSource({
       foo: { $envVar: { name: 'FOO', fallback: 42, allowNull: true } },
     });
 
     await expect(source.read([envVarDirective()])).rejects.toThrow();
   });
 
+  it('returns null when allowMissing', async () => {
+    process.env.BAR = 'foo';
+
+    const source = new LiteralSource({
+      foo: { $envVar: { name: 'FOO', allowMissing: true } },
+      bar: { $envVar: { name: 'BAR', allowMissing: true } },
+    });
+
+    const parsed = await source.read([envVarDirective()]);
+
+    expect(parsed.toJSON()).toEqual({ foo: null, bar: 'foo' });
+  });
+
   it('parses ints', async () => {
     process.env.FOO = '11';
 

app-config-extensions/src/env-var-directive.ts

@@ -86,17 +86,24 @@ export function envVarDirective(
         return parseValue(resolvedValue);
       }
 
-      if (typeof value === 'object' && value.fallback !== undefined) {
-        const fallback = (await parse(value.fallback)).toJSON();
-        const allowNull = (await parse(value.allowNull)).toJSON();
-
-        if (allowNull) {
-          validateStringOrNull(fallback, [...ctx, key, [InObject, 'fallback']]);
-        } else {
-          validateString(fallback, [...ctx, key, [InObject, 'fallback']]);
+      if (typeof value === 'object') {
+        if (value.fallback !== undefined) {
+          const fallback = (await parse(value.fallback)).toJSON();
+          const allowNull = (await parse(value.allowNull)).toJSON();
+
+          if (allowNull) {
+            validateStringOrNull(fallback, [...ctx, key, [InObject, 'fallback']]);
+          } else {
+            validateString(fallback, [...ctx, key, [InObject, 'fallback']]);
+          }
+
+          return parseValue(fallback);
         }
+        const allowMissing = (await parse(value.allowMissing)).toJSON();
 
-        return parseValue(fallback);
+        if (allowMissing) {
+          return parseValue(null);
+        }
       }
 
       throw new AppConfigError(`$envVar could not find ${name} environment variable`);