feat(calldata)!: move method-call key from "method" to "" (empty string)

src/abi/calldata/encoder.ts

@@ -142,6 +142,8 @@ export function encode(data: CalldataEncodable): Uint8Array {
 }
 
 // Constructs a calldata object for contract calls, omitting empty args/kwargs for compactness.
+// Method names use the empty-string key, which sorts first in canonical calldata encoding
+// and makes the method name a prefix of the encoded binary.
 export function makeCalldataObject(
   method: string | undefined,
   args: CalldataEncodable[] | undefined,
@@ -150,7 +152,7 @@ export function makeCalldataObject(
   let ret: {[key: string]: CalldataEncodable} = {};
 
   if (method) {
-    ret["method"] = method;
+    ret[""] = method;
   }
 
   if (args && args.length > 0) {

tests/calldata.test.ts

@@ -0,0 +1,35 @@
+import {describe, expect, it} from "vitest";
+import {calldata} from "@/abi";
+import type {CalldataEncodable} from "@/types/calldata";
+
+function decodeMap(data: Uint8Array): Map<string, CalldataEncodable> {
+  const decoded = calldata.decode(data);
+  expect(decoded).toBeInstanceOf(Map);
+  return decoded as Map<string, CalldataEncodable>;
+}
+
+describe("calldata method-call encoding", () => {
+  it("encodes method calls with the empty-string method key", () => {
+    const encoded = calldata.encode(calldata.makeCalldataObject("my_method", [1n, 2n], undefined));
+    const decoded = decodeMap(encoded);
+
+    expect(decoded.has("")).toBe(true);
+    expect(decoded.get("")).toBe("my_method");
+    expect(decoded.has("method")).toBe(false);
+  });
+
+  it("orders the empty method key before args in the encoded map body", () => {
+    const encoded = calldata.encode(calldata.makeCalldataObject("my_method", [1n, 2n], undefined));
+    const decoded = decodeMap(encoded);
+
+    expect(Array.from(decoded.entries())[0]).toEqual(["", "my_method"]);
+  });
+
+  it("orders the empty method key before kwargs in the encoded map body", () => {
+    const encoded = calldata.encode(calldata.makeCalldataObject("my_method", undefined, {count: 1n}));
+    const decoded = decodeMap(encoded);
+
+    expect(Array.from(decoded.entries())[0]).toEqual(["", "my_method"]);
+    expect(decoded.has("kwargs")).toBe(true);
+  });
+});