0.3.0

render.ts

@@ -58,12 +58,24 @@ export type ReverseMapManifest = {
 
 export type RenderOptions = {
   reverseMap?: boolean | string
+  /** When false, throw TargetExistsError instead of clearing a non-empty target. Defaults to true. */
+  overwrite?: boolean
+  /** Renames rendered file and directory names, e.g. `{ _gitignore: ".gitignore" }`. */
+  rename?: Record<string, string>
+}
+
+export class TargetExistsError extends Error {
+  constructor(target: string) {
+    super(`Refusing to overwrite non-empty target directory: ${target}`)
+    this.name = "TargetExistsError"
+  }
 }
 
 type RenderState = {
   sourceRoot: string
   destRoot: string
   manifest?: ReverseMapManifest
+  rename: Record<string, string>
 }
 
 function evalCondition(expr: string | undefined, context: Record<string, unknown>): boolean {
@@ -169,6 +181,7 @@ function getReverseMapPath(destRoot: string, reverseMap: true | string): string
 function getOutputName(
   entry: string,
   context: Record<string, unknown>,
+  rename: Record<string, string>,
   state?: RenderState,
   file?: ReverseMapFile,
 ): string | null {
@@ -188,7 +201,7 @@ function getOutputName(
     }
   }
 
-  return outputName.replace(VAR_RE, (_match, path: string) => {
+  const rendered = outputName.replace(VAR_RE, (_match, path: string) => {
     const result = String(resolveContext(context, path) ?? "")
     addReverseMapToken(state, file, {
       kind: "path",
@@ -200,6 +213,15 @@ function getOutputName(
     })
     return result
   })
+  return Object.hasOwn(rename, rendered) ? rename[rendered]! : rendered
+}
+
+function isNonEmptyTarget(destRoot: string): boolean {
+  try {
+    return !statSync(destRoot).isDirectory() || readdirSync(destRoot).length > 0
+  } catch {
+    return false
+  }
 }
 
 function isUtf8Text(buffer: Buffer): boolean {
@@ -450,10 +472,14 @@ function renderDir(
     sourceRoot,
     destRoot,
     manifest: options.reverseMap ? createReverseMapManifest() : undefined,
+    rename: options.rename ?? {},
   }
   const mapPath = options.reverseMap ? getReverseMapPath(destRoot, options.reverseMap) : undefined
   assertSafeRenderTarget(srcDir, destDir)
-  validateOutputPaths(srcDir, destRoot, context)
+  validateOutputPaths(srcDir, destRoot, context, state.rename)
+  if (options.overwrite === false && isNonEmptyTarget(destRoot)) {
+    throw new TargetExistsError(destDir)
+  }
   rmSync(destDir, { recursive: true, force: true })
   renderDirInner(srcDir, destRoot, context, state)
   if (state.manifest && mapPath) {
@@ -466,18 +492,19 @@ function validateOutputPaths(
   srcDir: string,
   destDir: string,
   context: Record<string, unknown>,
+  rename: Record<string, string>,
 ) {
   const entries = readdirSync(srcDir).sort()
 
   for (const entry of entries) {
     const srcPath = resolvePath(srcDir, entry)
     const stat = statSync(srcPath)
-    const outputName = getOutputName(entry, context)
+    const outputName = getOutputName(entry, context, rename)
     if (outputName === null) continue
 
     const destPath = resolveOutputPath(destDir, outputName)
     if (stat.isDirectory()) {
-      validateOutputPaths(srcPath, destPath, context)
+      validateOutputPaths(srcPath, destPath, context, rename)
     }
   }
 }
@@ -533,7 +560,7 @@ function renderDirInner(
       templatePath,
       tokens: [],
     }
-    const outputName = getOutputName(entry, context, state, tempFile)
+    const outputName = getOutputName(entry, context, state.rename, state, tempFile)
     if (outputName === null) {
       storeSkippedTemplate(srcPath, state)
       continue