force the tracker to derive next indices if a hole is detected

lib/db/mysql-db-wrapper.js

@@ -931,6 +931,36 @@ class MySqlDbWrapper {
     return ret
   }
 
+  /**
+   * Get the number of indices derived in an interval for a HD chain
+   * @param {string} xpub - xpub
+   * @param {integer} chain - HD chain (0 or 1)
+   * @param {integer} minIdx - min index of derivation
+   * @param {integer} maxIdx - max index of derivation
+   * @returns {integer[]} returns an array of number of derived indices
+   */
+  async getHDAccountNbDerivedIndices(xpub, chain, minIdx, maxIdx) {
+    const sqlQuery = 'SELECT \
+        COUNT(`hd_addresses`.`hdAddrIndex`) AS `nbDerivedIndices` \
+      FROM `hd_addresses` \
+      INNER JOIN `hd` ON `hd_addresses`.`hdID` = `hd`.`hdID` \
+      WHERE `hd`.`hdXpub` = ? \
+      AND `hd_addresses`.`hdAddrChain` = ? \
+      AND `hd_addresses`.`hdAddrIndex` >= ? \
+      AND `hd_addresses`.`hdAddrIndex` <= ?'
+
+    const params = [xpub, chain, minIdx, maxIdx]
+    const query = mysql.format(sqlQuery, params)
+    const results = await this._query(query)
+
+    if (results.length == 1) {
+      const nbDerivedIndices = results[0].nbDerivedIndices
+      return (nbDerivedIndices == null) ? 0 : nbDerivedIndices
+    }
+
+    return 0
+  }
+
   /**
    * Get the number of transactions for an HD account
    * @param {string} xpub - xpub

tracker/transaction.js

@@ -333,9 +333,24 @@ class Transaction {
       if (chainMaxUsedIndex < unusedIndices[chain])
         continue
 
-      // If max derived index is beyond max used index plus gap limit, move on
-      if (derivedIndices[chain] >= chainMaxUsedIndex + gapLimit[chain])
-        continue
+      // If max derived index is beyond max used index plus gap limit.
+      if (derivedIndices[chain] >= chainMaxUsedIndex + gapLimit[chain]) {
+        // Check that we don't have a hole in the next <gapLimit> indices
+        const nbDerivedIndicesForward = await db.getHDAccountNbDerivedIndices(
+          xpub,
+          chain,
+          chainMaxUsedIndex,
+          chainMaxUsedIndex + gapLimit[chain]
+        )
+
+        if (nbDerivedIndicesForward < gapLimit[chain] + 1) {
+          // Hole detected. Force derivation.
+          derivedIndices[chain] = chainMaxUsedIndex
+        } else {
+          // Move on
+          continue
+        }
+      }
 
       let done