txdb: fix limit on value coin selector.

lib/wallet/txdb.js

@@ -3821,7 +3821,7 @@ class TXDB {
    * @param {Object} [options]
    * @param {Number} [options.minValue=0]
    * @param {Number} [options.maxValue=MAX_MONEY]
-   * @param {Number} [options.limit=-1]
+   * @param {Number?} [options.limit]
    * @param {Boolean} [options.reverse=false]
    * @param {Boolean} [options.inclusive=true]
    * @returns {AsyncGenerator<Credit>}
@@ -3872,6 +3872,7 @@ class TXDB {
     iterOpts[lesser] = max;
 
     const iter = this.bucket.iterator(iterOpts);
+    let items = 0;
 
     for await (const key of iter.keysAsync()) {
       const decoded = prefix.decode(key);
@@ -3881,6 +3882,7 @@ class TXDB {
 
       assert(credit);
       yield credit;
+      items++;
     }
 
     // now process unconfirmed.
@@ -3897,6 +3899,13 @@ class TXDB {
     iterOpts[greater] = min;
     iterOpts[lesser] = max;
 
+    if (limit != null && limit > 0) {
+      if (items >= limit)
+        return;
+
+      iterOpts.limit = limit - items;
+    }
+
     const ucIter = this.bucket.iterator(iterOpts);
 
     for await (const key of ucIter.keysAsync()) {

test/wallet-coinselection-test.js

@@ -102,6 +102,17 @@ describe('Wallet Coin Selection', function() {
 
     let isSorted, getCredits;
     const sumCredits = credits => credits.reduce((acc, c) => acc + c.coin.value, 0);
+    const checkWithLimits = async (credits, wallet, acct) => {
+      for (let i = 1; i < credits.length; i++) {
+        const creditsLimit = await getCredits(wallet, acct, {
+          limit: i
+        });
+        assert.strictEqual(creditsLimit.length, i);
+        assert(isSorted(creditsLimit), 'Credits not sorted.');
+        assert.deepStrictEqual(creditsLimit, credits.slice(0, i));
+        assert(sumCredits(creditsLimit) === sumCredits(credits.slice(0, i)));
+      }
+    };
 
     before(() => {
       switch (indexType) {
@@ -631,15 +642,21 @@ describe('Wallet Coin Selection', function() {
       assert(isSorted(credits0), 'Credits not sorted.');
       assert(sumCredits(credits0) === sum0);
 
+      await checkWithLimits(credits0, wallet);
+
       const credits1 = await getCredits(wallet, 1);
       assert.strictEqual(credits1.length, 4);
       assert(isSorted(credits1), 'Credits not sorted.');
       assert(sumCredits(credits1) === sum1);
 
+      await checkWithLimits(credits1, wallet, 1);
+
       const both = await getCredits(wallet, -1);
       assert.strictEqual(both.length, 8);
       assert(isSorted(both), 'Credits not sorted.');
       assert(sumCredits(both) === sum0 + sum1);
+
+      await checkWithLimits(both, wallet, -1);
     });
   });
   }