fix: fix default build dir not relative to source dir (#269)

* test: fix get action inputs test when source dir specified

* fix: default build dir should relative to source dir

* ci: fix test directory location

src/inputs.test.ts

@@ -1,4 +1,5 @@
 import { jest } from "@jest/globals";
+import path from "node:path";
 import type { Inputs } from "./inputs.js";
 
 jest.unstable_mockModule("@actions/core", () => ({
@@ -23,13 +24,27 @@ describe("get action inputs", () => {
     {
       name: "with source directory specified",
       stringInputs: { "source-dir": "project" },
-      expectedInputs: { sourceDir: "project" },
+      expectedInputs: {
+        sourceDir: "project",
+        buildDir: path.join("project", "build"),
+      },
     },
     {
       name: "with build directory specified",
       stringInputs: { "build-dir": "output" },
       expectedInputs: { buildDir: "output" },
     },
+    {
+      name: "with source and build directories specified",
+      stringInputs: {
+        "source-dir": "project",
+        "build-dir": "output",
+      },
+      expectedInputs: {
+        sourceDir: "project",
+        buildDir: "output",
+      },
+    },
     {
       name: "with generator specified",
       stringInputs: { generator: "Ninja" },

src/inputs.ts

@@ -1,4 +1,5 @@
 import { getBooleanInput, getInput, getMultilineInput } from "@actions/core";
+import path from "node:path";
 
 export interface Inputs {
   sourceDir: string;
@@ -15,9 +16,10 @@ export interface Inputs {
 }
 
 export function getInputs(): Inputs {
+  const sourceDir = getInput("source-dir") || ".";
   return {
-    sourceDir: getInput("source-dir") || ".",
-    buildDir: getInput("build-dir") || "build",
+    sourceDir,
+    buildDir: getInput("build-dir") || path.join(sourceDir, "build"),
     generator: getInput("generator"),
     cCompiler: getInput("c-compiler"),
     cxxCompiler: getInput("cxx-compiler"),