From eecf09f51564df4f63139f26e65efa1102a9958d Mon Sep 17 00:00:00 2001
From: Greg Hysen <greg.hysen@gmail.com>
Date: Mon, 9 Apr 2018 11:55:23 -0700
Subject: Added a detailed description of `renameOverloadedMethods` (special
 thanks to @fabioberger). Updated Javascript styles in the Abi-Gen and Utils
 packages, around support for function overloading.

---
 packages/utils/src/abi_utils.ts | 85 ++++++++++++++++++++---------------------
 1 file changed, 41 insertions(+), 44 deletions(-)

(limited to 'packages/utils/src')

diff --git a/packages/utils/src/abi_utils.ts b/packages/utils/src/abi_utils.ts
index 843b8589b..c4533d42e 100644
--- a/packages/utils/src/abi_utils.ts
+++ b/packages/utils/src/abi_utils.ts
@@ -12,63 +12,60 @@ export const abiUtils = {
         }
         return param.type;
     },
-    getFunctionSignature(abi: MethodAbi): string {
-        const functionName = abi.name;
-        const parameterTypeList = abi.inputs.map((param: DataItem) => this.parseFunctionParam(param));
+    getFunctionSignature(methodAbi: MethodAbi): string {
+        const functionName = methodAbi.name;
+        const parameterTypeList = _.map(methodAbi.inputs, (param: DataItem) => this.parseFunctionParam(param));
         const functionSignature = `${functionName}(${parameterTypeList})`;
         return functionSignature;
     },
+    /**
+     * Solidity supports function overloading whereas TypeScript does not.
+     * See: https://solidity.readthedocs.io/en/v0.4.21/contracts.html?highlight=overload#function-overloading
+     * In order to support overloaded functions, we suffix overloaded function names with an index.
+     * This index should be deterministic, regardless of function ordering within the smart contract. To do so,
+     * we assign indexes based on the alphabetical order of function signatures.
+     *
+     * E.g
+     * ['f(uint)', 'f(uint,byte32)']
+     * Should always be renamed to:
+     * ['f1(uint)', 'f2(uint,byte32)']
+     * Regardless of the order in which these these overloaded functions are declared within the contract ABI.
+     */
     renameOverloadedMethods(inputContractAbi: ContractAbi): ContractAbi {
         const contractAbi = _.cloneDeep(inputContractAbi);
         const methodAbis = contractAbi.filter((abi: AbiDefinition) => abi.type === AbiType.Function) as MethodAbi[];
-        const methodAbisByOriginalIndex = _.transform(
-            methodAbis,
-            (result: Array<{ index: number; methodAbi: MethodAbi }>, methodAbi, i: number) => {
-                result.push({ index: i, methodAbi });
-            },
-            [],
-        );
         // Sort method Abis into alphabetical order, by function signature
-        const methodAbisByOriginalIndexOrdered = _.sortBy(methodAbisByOriginalIndex, [
-            (entry: { index: number; methodAbi: MethodAbi }) => {
-                const functionSignature = this.getFunctionSignature(entry.methodAbi);
+        const methodAbisOrdered = _.sortBy(methodAbis, [
+            (methodAbi: MethodAbi) => {
+                const functionSignature = this.getFunctionSignature(methodAbi);
                 return functionSignature;
             },
         ]);
         // Group method Abis by name (overloaded methods will be grouped together, in alphabetical order)
-        const methodAbisByName = _.transform(
-            methodAbisByOriginalIndexOrdered,
-            (result: { [key: string]: Array<{ index: number; methodAbi: MethodAbi }> }, entry) => {
-                (result[entry.methodAbi.name] || (result[entry.methodAbi.name] = [])).push(entry);
-            },
-            {},
-        );
-        // Rename overloaded methods to overloadedMethoName_1, overloadedMethoName_2, ...
-        const methodAbisRenamed = _.transform(
-            methodAbisByName,
-            (result: MethodAbi[], methodAbisWithSameName: Array<{ index: number; methodAbi: MethodAbi }>) => {
-                _.forEach(methodAbisWithSameName, (entry, i: number) => {
-                    if (methodAbisWithSameName.length > 1) {
-                        const overloadedMethodId = i + 1;
-                        const sanitizedMethodName = `${entry.methodAbi.name}_${overloadedMethodId}`;
-                        const indexOfExistingAbiWithSanitizedMethodNameIfExists = _.findIndex(
-                            methodAbis,
-                            methodAbi => methodAbi.name === sanitizedMethodName,
+        const methodAbisByName: { [key: string]: MethodAbi[] } = {};
+        _.each(methodAbisOrdered, methodAbi => {
+            (methodAbisByName[methodAbi.name] || (methodAbisByName[methodAbi.name] = [])).push(methodAbi);
+        });
+        // Rename overloaded methods to overloadedMethodName1, overloadedMethodName2, ...
+        _.each(methodAbisByName, methodAbisWithSameName => {
+            _.each(methodAbisWithSameName, (methodAbi, i: number) => {
+                if (methodAbisWithSameName.length > 1) {
+                    const overloadedMethodId = i + 1;
+                    const sanitizedMethodName = `${methodAbi.name}${overloadedMethodId}`;
+                    const indexOfExistingAbiWithSanitizedMethodNameIfExists = _.findIndex(
+                        methodAbis,
+                        currentMethodAbi => currentMethodAbi.name === sanitizedMethodName,
+                    );
+                    if (indexOfExistingAbiWithSanitizedMethodNameIfExists >= 0) {
+                        const methodName = methodAbi.name;
+                        throw new Error(
+                            `Failed to rename overloaded method '${methodName}' to '${sanitizedMethodName}'. A method with this name already exists.`,
                         );
-                        if (indexOfExistingAbiWithSanitizedMethodNameIfExists >= 0) {
-                            const methodName = entry.methodAbi.name;
-                            throw new Error(
-                                `Failed to rename overloaded method '${methodName}' to '${sanitizedMethodName}'. A method with this name already exists.`,
-                            );
-                        }
-                        entry.methodAbi.name = sanitizedMethodName;
                     }
-                    // Add method to list of ABIs in its original position
-                    result.splice(entry.index, 0, entry.methodAbi);
-                });
-            },
-            [...Array(methodAbis.length)],
-        );
+                    methodAbi.name = sanitizedMethodName;
+                }
+            });
+        });
         return contractAbi;
     },
 };
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