Refactor transpile "main" path validation

cli/build/register.ts

@@ -14,6 +14,7 @@ import { generateKicadProject } from "./generate-kicad-project"
 import type { GeneratedKicadProject } from "./generate-kicad-project"
 import { generateKicadFootprintLibrary } from "./generate-kicad-footprint-library"
 import { transpileFile } from "./transpile"
+import { validateMainInDist } from "../utils/validate-main-in-dist"
 
 // @ts-ignore
 import runFrameStandaloneBundleContent from "@tscircuit/runframe/standalone" with {
@@ -184,6 +185,8 @@ export const registerBuild = (program: Command) => {
           }
 
           if (options?.transpile) {
+            validateMainInDist(projectDir, distDir)
+
             console.log("Transpiling entry file...")
             const entryFile = mainEntrypoint || circuitFiles[0]
             if (!entryFile) {

cli/transpile/register.ts

@@ -1,8 +1,8 @@
 import type { Command } from "commander"
-import fs from "node:fs"
 import path from "node:path"
 import { transpileFile } from "../build/transpile/index"
 import { getBuildEntrypoints } from "../build/get-build-entrypoints"
+import { validateMainInDist } from "../utils/validate-main-in-dist"
 
 export const registerTranspile = (program: Command) => {
   program
@@ -20,25 +20,7 @@ export const registerTranspile = (program: Command) => {
 
         const distDir = path.join(projectDir, "dist")
 
-        const packageJsonPath = path.join(projectDir, "package.json")
-        if (fs.existsSync(packageJsonPath)) {
-          const packageJson = JSON.parse(
-            fs.readFileSync(packageJsonPath, "utf-8"),
-          )
-
-          if (typeof packageJson.main === "string") {
-            const resolvedMainPath = path.resolve(projectDir, packageJson.main)
-            const isMainInDist =
-              resolvedMainPath === distDir ||
-              resolvedMainPath.startsWith(`${distDir}${path.sep}`)
-
-            if (!isMainInDist) {
-              throw new Error(
-                'When using transpilation, your package\'s "main" field should point inside the `dist/*` directory, usually to "dist/index.js"',
-              )
-            }
-          }
-        }
+        validateMainInDist(projectDir, distDir)
 
         console.log("Transpiling entry file...")
         const entryFile = mainEntrypoint || circuitFiles[0]

cli/utils/validate-main-in-dist.ts

@@ -0,0 +1,22 @@
+import fs from "node:fs"
+import path from "node:path"
+
+export const validateMainInDist = (projectDir: string, distDir: string) => {
+  const packageJsonPath = path.join(projectDir, "package.json")
+  if (!fs.existsSync(packageJsonPath)) return
+
+  const packageJson = JSON.parse(fs.readFileSync(packageJsonPath, "utf-8"))
+
+  if (typeof packageJson.main !== "string") return
+
+  const resolvedMainPath = path.resolve(projectDir, packageJson.main)
+  const isMainInDist =
+    resolvedMainPath === distDir ||
+    resolvedMainPath.startsWith(`${distDir}${path.sep}`)
+
+  if (!isMainInDist) {
+    throw new Error(
+      'When using transpilation, your package\'s "main" field should point inside the `dist/*` directory, usually to "dist/index.js"',
+    )
+  }
+}

tests/cli/build/build-transpile.test.ts

@@ -60,7 +60,7 @@ test("build with --transpile uses mainEntrypoint when available", async () => {
   await writeFile(otherPath, circuitCode)
   await writeFile(
     path.join(tmpDir, "package.json"),
-    JSON.stringify({ main: "index.tsx" }),
+    JSON.stringify({ main: "dist/index.js" }),
   )
 
   await runCommand(`tsci build --transpile --ignore-errors`)
@@ -79,6 +79,23 @@ test("build with --transpile uses mainEntrypoint when available", async () => {
   expect(dtsStat.isFile()).toBe(true)
 }, 30_000)
 
+test("build with --transpile errors when main is outside dist", async () => {
+  const { tmpDir, runCommand } = await getCliTestFixture()
+  const mainPath = path.join(tmpDir, "index.tsx")
+
+  await writeFile(mainPath, circuitCode)
+  await writeFile(
+    path.join(tmpDir, "package.json"),
+    JSON.stringify({ main: "index.tsx" }),
+  )
+
+  const { stderr } = await runCommand(`tsci build --transpile`)
+
+  expect(stderr).toContain(
+    'When using transpilation, your package\'s "main" field should point inside the `dist/*` directory, usually to "dist/index.js"',
+  )
+}, 30_000)
+
 test("build with --transpile transforms JSX correctly", async () => {
   const { tmpDir, runCommand } = await getCliTestFixture()
   const circuitPath = path.join(tmpDir, "jsx-test.tsx")