feat: validate enter-side amount intent for ERC-4626 vaults (ENG-2418, ENG-2419)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@yieldxyz/shield",
-  "version": "1.3.0",
+  "version": "1.4.0",
   "description": "Zero-trust transaction validation library for Yield.xyz integrations.",
   "packageManager": "pnpm@10.33.1",
   "engines": {

src/json/handler.test.ts

@@ -233,6 +233,74 @@ describe('handleJsonRequest', () => {
     });
   });
 
+  describe('schema: args.amount and args.decimals boundaries', () => {
+    const userAddress = '0x742d35cc6634c0532925a3b844bc9e7595f0beb8';
+    const referralAddress = '0x371240E80Bf84eC2bA8b55aE2fD0B467b16Db2be';
+    const validLidoStakeTx = {
+      to: '0xae7ab96520DE3A18E5e111B5EaAb095312D7fE84',
+      from: userAddress,
+      value: '0xde0b6b3a7640000',
+      data: '0xa1903eab' + referralAddress.slice(2).padStart(64, '0'),
+      chainId: 1,
+    };
+    // 78 decimal digits — the schema's maxLength for args.amount
+    const MAX_UINT256_STRING = (2n ** 256n - 1n).toString();
+    const validRequest = (args: object) => ({
+      apiVersion: '1.0',
+      operation: 'validate',
+      yieldId: 'ethereum-eth-lido-staking',
+      unsignedTransaction: JSON.stringify(validLidoStakeTx),
+      userAddress,
+      args,
+    });
+    it('accepts args.decimals as an integer', () => {
+      const response = call(validRequest({ amount: '1000000', decimals: 6 }));
+      // Schema accepted (not a SCHEMA_VALIDATION_ERROR) and the request
+      // proceeded to actual validation.
+      expect(response.ok).toBe(true);
+      expect(response.result.isValid).toBe(true);
+    });
+    it('accepts args.decimals at the bounds (0 and 255)', () => {
+      const zero = call(validRequest({ decimals: 0 }));
+      expect(zero.ok).toBe(true);
+      const max = call(validRequest({ decimals: 255 }));
+      expect(max.ok).toBe(true);
+    });
+    it('rejects fractional args.decimals', () => {
+      const response = call(validRequest({ decimals: 6.5 }));
+      expect(response.ok).toBe(false);
+      expect(response.error.code).toBe('SCHEMA_VALIDATION_ERROR');
+    });
+    it('rejects args.decimals above 255', () => {
+      const response = call(validRequest({ decimals: 256 }));
+      expect(response.ok).toBe(false);
+      expect(response.error.code).toBe('SCHEMA_VALIDATION_ERROR');
+    });
+    it('rejects negative args.decimals', () => {
+      const response = call(validRequest({ decimals: -1 }));
+      expect(response.ok).toBe(false);
+      expect(response.error.code).toBe('SCHEMA_VALIDATION_ERROR');
+    });
+    it('rejects non-numeric args.decimals', () => {
+      const response = call(validRequest({ decimals: '6' }));
+      expect(response.ok).toBe(false);
+      expect(response.error.code).toBe('SCHEMA_VALIDATION_ERROR');
+    });
+    it('accepts a 78-digit args.amount (maxUint256)', () => {
+      expect(MAX_UINT256_STRING.length).toBe(78); // pin the schema boundary
+      const response = call(validRequest({ amount: MAX_UINT256_STRING }));
+      expect(response.ok).toBe(true);
+      // Lido ignores args.amount today (amount validation is ERC-4626-only in
+      // Phase 1), so a valid stake tx still validates.
+      expect(response.result.isValid).toBe(true);
+    });
+    it('rejects args.amount longer than 78 characters', () => {
+      const response = call(validRequest({ amount: '1'.repeat(79) }));
+      expect(response.ok).toBe(false);
+      expect(response.error.code).toBe('SCHEMA_VALIDATION_ERROR');
+    });
+  });
+
   describe('isSupported operation', () => {
     it('should return supported: true for known yield', () => {
       const response = call({

src/json/schema.ts

@@ -41,6 +41,7 @@ export const requestSchema = {
 
         // Future use - include for forward compatibility
         amount: { type: 'string', maxLength: 78 }, // Max uint256 is 78 digits
+        decimals: { type: 'integer', minimum: 0, maximum: 255 },
         tronResource: { type: 'string', enum: ['BANDWIDTH', 'ENERGY'] },
         providerId: { type: 'string', maxLength: 256 },
         duration: { type: 'number', minimum: 0 },

src/types/index.ts

@@ -16,6 +16,7 @@ export interface ValidationResult {
 
 export type ActionArguments = {
   amount?: string;
+  decimals?: number; // declared-amount token decimals (intent context)
   validatorAddress?: string;
   validatorAddresses?: string[];
   tronResource?: TronResourceType;

src/utils/amount.test.ts

@@ -0,0 +1,50 @@
+import { MAX_UINT256, matchesDeclaredAmount } from './amount';
+
+describe('MAX_UINT256', () => {
+  it('equals 2^256 - 1', () => {
+    expect(MAX_UINT256).toBe(2n ** 256n - 1n);
+  });
+});
+
+describe('matchesDeclaredAmount', () => {
+  const DECLARED = '1000000'; // 1 USDC (6 decimals), wei
+
+  it('returns true on exact match', () => {
+    expect(matchesDeclaredAmount(1000000n, DECLARED)).toBe(true);
+  });
+
+  it('returns false when calldata amount is one above declared', () => {
+    expect(matchesDeclaredAmount(1000001n, DECLARED)).toBe(false);
+  });
+
+  it('returns false when calldata amount is one below declared', () => {
+    expect(matchesDeclaredAmount(999999n, DECLARED)).toBe(false);
+  });
+
+  it('returns false on gross inflation', () => {
+    expect(matchesDeclaredAmount(1000000000000n, DECLARED)).toBe(false);
+  });
+
+  it('returns true when declared is undefined (opt-in skip)', () => {
+    expect(matchesDeclaredAmount(123456789n, undefined)).toBe(true);
+  });
+
+  it('matches maxUint256 against a declared maxUint256 (sanctioned infinite)', () => {
+    expect(matchesDeclaredAmount(MAX_UINT256, MAX_UINT256.toString())).toBe(
+      true,
+    );
+  });
+
+  it('rejects maxUint256 against a finite declared amount', () => {
+    expect(matchesDeclaredAmount(MAX_UINT256, DECLARED)).toBe(false);
+  });
+
+  it('matches zero against declared "0"', () => {
+    expect(matchesDeclaredAmount(0n, '0')).toBe(true);
+  });
+
+  it('throws on a malformed declared string (fail-safe: Shield.validate catches per-type throws)', () => {
+    expect(() => matchesDeclaredAmount(1000000n, '1.5')).toThrow();
+    expect(() => matchesDeclaredAmount(1000000n, 'abc')).toThrow();
+  });
+});

src/utils/amount.ts

@@ -0,0 +1,10 @@
+export const MAX_UINT256 = (1n << 256n) - 1n;
+
+// Opt-in: undefined declared amount → skip (returns true).
+export function matchesDeclaredAmount(
+  calldataAmount: bigint,
+  declared?: string,
+): boolean {
+  if (declared === undefined) return true;
+  return calldataAmount === BigInt(declared);
+}