chore: add new parse function with tests

src/lib/util/parseEnvVar.test.ts

@@ -1,6 +1,7 @@
 import {
     parseEnvVarBoolean,
     parseEnvVarNumber,
+    parseEnvVarNumberWithBounds,
     parseEnvVarStrings,
 } from './parseEnvVar';
 
@@ -39,3 +40,36 @@ test('parseEnvVarStringList', () => {
     expect(parseEnvVarStrings('a,b,c', [])).toEqual(['a', 'b', 'c']);
     expect(parseEnvVarStrings(' a,,,b,  c , ,', [])).toEqual(['a', 'b', 'c']);
 });
+
+describe('parseEnvVarNumberWithBounds', () => {
+    const parse = parseEnvVarNumberWithBounds;
+    test('works the same as parseEnvVarNumber', () => {
+        expect(parse('', { fallback: 1 })).toEqual(1);
+        expect(parse(' ', { fallback: 1 })).toEqual(1);
+        expect(parse('a', { fallback: 1 })).toEqual(1);
+        expect(parse('1', { fallback: 1 })).toEqual(1);
+        expect(parse('2', { fallback: 1 })).toEqual(2);
+        expect(parse('2e2', { fallback: 1 })).toEqual(2);
+        expect(parse('-1', { fallback: 1 })).toEqual(-1);
+    });
+
+    test('prefers options override over default value if present', () => {
+        expect(parse('', { fallback: 1, optionsOverride: 2 })).toEqual(2);
+    });
+
+    test('accepts 0 as options override', () => {
+        expect(parse('', { fallback: 1, optionsOverride: 0 })).toEqual(0);
+    });
+
+    test('prefers env var over options override', () => {
+        expect(parse('5', { fallback: 1, optionsOverride: 2 })).toEqual(5);
+    });
+
+    test('clamps the number to greater than or equal to the min number if provided', () => {
+        expect(parse('1', { fallback: 0, min: 2 })).toEqual(2);
+        expect(parse('', { fallback: 0, min: 2 })).toEqual(2);
+        expect(parse('', { fallback: 0, optionsOverride: 1, min: 2 })).toEqual(
+            2,
+        );
+    });
+});

src/lib/util/parseEnvVar.ts

@@ -38,3 +38,22 @@ export function parseEnvVarStrings(
 
     return defaultVal;
 }
+
+type parseEnvVarNumberWithBoundsOptions = {
+    fallback: number;
+    min?: number;
+    optionsOverride?: number;
+};
+
+export function parseEnvVarNumberWithBounds(
+    envVar: string | undefined,
+    { min, fallback, optionsOverride }: parseEnvVarNumberWithBoundsOptions,
+): number {
+    const parsed = parseEnvVarNumber(envVar, optionsOverride ?? fallback);
+
+    if (min) {
+        return Math.max(min, parsed);
+    }
+
+    return parsed;
+}