fix: handle scientific notation in bigintConfigHelper

yarn-project/foundation/src/config/config.test.ts

@@ -1,6 +1,6 @@
 import { jest } from '@jest/globals';
 
-import { type ConfigMappingsType, getConfigFromMappings, numberConfigHelper } from './index.js';
+import { type ConfigMappingsType, bigintConfigHelper, getConfigFromMappings, numberConfigHelper } from './index.js';
 
 describe('Config', () => {
   describe('getConfigFromMappings', () => {
@@ -131,4 +131,37 @@ describe('Config', () => {
       });
     });
   });
+
+  describe('bigintConfigHelper', () => {
+    it('parses plain integer strings', () => {
+      const { parseEnv } = bigintConfigHelper();
+      expect(parseEnv!('123')).toBe(123n);
+      expect(parseEnv!('0')).toBe(0n);
+      expect(parseEnv!('200000000000000000000000')).toBe(200000000000000000000000n);
+    });
+
+    it('parses scientific notation', () => {
+      const { parseEnv } = bigintConfigHelper();
+      expect(parseEnv!('1e+23')).toBe(100000000000000000000000n);
+      expect(parseEnv!('2E+23')).toBe(200000000000000000000000n);
+      expect(parseEnv!('1e23')).toBe(100000000000000000000000n);
+      expect(parseEnv!('5e18')).toBe(5000000000000000000n);
+    });
+
+    it('parses scientific notation with decimal mantissa', () => {
+      const { parseEnv } = bigintConfigHelper();
+      expect(parseEnv!('1.5e10')).toBe(15000000000n);
+      expect(parseEnv!('2.5e5')).toBe(250000n);
+    });
+
+    it('returns default value for empty string', () => {
+      const { parseEnv } = bigintConfigHelper(42n);
+      expect(parseEnv!('')).toBe(42n);
+    });
+
+    it('throws for non-integer scientific notation results', () => {
+      const { parseEnv } = bigintConfigHelper();
+      expect(() => parseEnv!('1e-3')).toThrow();
+    });
+  });
 });

yarn-project/foundation/src/config/index.ts

@@ -177,6 +177,21 @@ export function bigintConfigHelper(defaultVal?: bigint): Pick<ConfigMapping, 'pa
       if (val === '') {
         return defaultVal;
       }
+      // Handle scientific notation (e.g. "1e+23", "2E23") which BigInt() doesn't accept directly.
+      // We parse it losslessly using bigint arithmetic instead of going through float64.
+      if (/[eE]/.test(val)) {
+        const match = val.match(/^(-?\d+(?:\.(\d+))?)[eE]([+-]?\d+)$/);
+        if (!match) {
+          throw new Error(`Cannot convert '${val}' to a BigInt`);
+        }
+        const digits = match[1].replace('.', '');
+        const decimalPlaces = match[2]?.length ?? 0;
+        const exponent = parseInt(match[3], 10) - decimalPlaces;
+        if (exponent < 0) {
+          throw new Error(`Cannot convert '${val}' to a BigInt: result is not an integer`);
+        }
+        return BigInt(digits) * 10n ** BigInt(exponent);
+      }
       return BigInt(val);
     },
     defaultValue: defaultVal,