Static analysis: Add module for deletion from dynamic array

remix-analyzer/src/solidity-analyzer/modules/list.js

@@ -15,5 +15,6 @@ module.exports = [
   require('./deleteDynamicArrays'),
   require('./assignAndCompare'),
   require('./erc20Decimals'),
-  require('./stringBytesLength')
+  require('./stringBytesLength'),
+  require('./deleteFromDynamicArray')
 ]

remix-analyzer/src/solidity-analyzer/modules/staticAnalysisCommon.js

@@ -501,6 +501,24 @@ function isDynamicArrayAccess (node) {
   return node && nodeType(node, exactMatch(nodeTypes.IDENTIFIER)) && (node.attributes.type.endsWith('[] storage ref') || node.attributes.type === 'bytes storage ref' || node.attributes.type === 'string storage ref')
 }
 
+/**
+ * True if node is a delete instruction for an element from a dynamic array
+ * @node {ASTNode} node to check for
+ * @return {bool}
+ */
+function isDeleteFromDynamicArray (node) {
+  return isDeleteUnaryOperation(node) && isIndexAccess(node.children[0])
+}
+
+/**
+ * True if node is the access of an index
+ * @node {ASTNode} node to check for
+ * @return {bool}
+ */
+function isIndexAccess (node) {
+  return node && node.name === 'IndexAccess'
+}
+
 /**
  * True if call to code within the current contracts context including (delegate) library call
  * @node {ASTNode} some AstNode
@@ -999,9 +1017,11 @@ module.exports = {
 
   // #################### Complex Node Identification
   isDeleteOfDynamicArray: isDeleteOfDynamicArray,
+  isDeleteFromDynamicArray: isDeleteFromDynamicArray,
   isAbiNamespaceCall: isAbiNamespaceCall,
   isSpecialVariableAccess: isSpecialVariableAccess,
   isDynamicArrayAccess: isDynamicArrayAccess,
+  isIndexAccess: isIndexAccess,
   isSubScopeWithTopLevelUnAssignedBinOp: isSubScopeWithTopLevelUnAssignedBinOp,
   hasFunctionBody: hasFunctionBody,
   isInteraction: isInteraction,

remix-solidity/src/analysis/modules/deleteFromDynamicArray.js

@@ -0,0 +1,29 @@
+var name = 'Delete from dynamic Array: '
+var desc = 'Using delete on an array leaves a gap'
+var categories = require('./categories')
+var common = require('./staticAnalysisCommon')
+
+function deleteFromDynamicArray () {
+  this.relevantNodes = []
+}
+
+deleteFromDynamicArray.prototype.visit = function (node) {
+  if (common.isDeleteFromDynamicArray(node)) this.relevantNodes.push(node)
+}
+
+deleteFromDynamicArray.prototype.report = function (compilationResults) {
+  return this.relevantNodes.map((node) => {
+    return {
+      warning: 'Using delete on an array leaves a gap. The length of the array remains the same. If you want to remove the empty position you need to shift items manually and update the length property.\n',
+      location: node.src,
+      more: 'https://github.com/miguelmota/solidity-idiosyncrasies'
+    }
+  })
+}
+
+module.exports = {
+  name: name,
+  description: desc,
+  category: categories.MISC,
+  Module: deleteFromDynamicArray
+}