Allow nancy to write to stdout when output is a single file

README.md

@@ -42,7 +42,7 @@ A simple templating system.
 
 positional arguments:
   INPUT-PATH   list of input directories, or a single file
-  OUTPUT       output directory, or file
+  OUTPUT       output directory, or file ('-' for stdout)
 
 optional arguments:
   -h, --help   show this help message and exit
@@ -71,6 +71,10 @@ convenient to expand a single file using the command:
 
 `nancy INPUT-FILE OUTPUT-FILE`
 
+Also, when the output is a single file, the special filename `-` may be used
+to cause Nancy to print the result to standard output instead of writing it
+to a file.
+
 For each directory in the input tree, Nancy creates a corresponding
 directory, if it does not already exist.
 

README.nancy.md

@@ -56,6 +56,10 @@ convenient to expand a single file using the command:
 
 `nancy INPUT-FILE OUTPUT-FILE`
 
+Also, when the output is a single file, the special filename `-` may be used
+to cause Nancy to print the result to standard output instead of writing it
+to a file.
+
 For each directory in the input tree, Nancy creates a corresponding
 directory, if it does not already exist.
 

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@sc3d/nancy",
   "description": "Simple templating system",
-  "version": "7.3.1",
+  "version": "7.4.0",
   "author": "Reuben Thomas",
   "bin": {
     "nancy": "bin/run.js"

src/cli.ts

@@ -13,7 +13,7 @@ const parser = new ArgumentParser({
     + 'are merged in left-to-right order.',
 })
 parser.add_argument('input', {metavar: 'INPUT-PATH', help: 'list of input directories, or a single file'})
-parser.add_argument('output', {metavar: 'OUTPUT', help: 'output directory, or file'})
+parser.add_argument('output', {metavar: 'OUTPUT', help: "output directory, or file ('-' for stdout)"})
 parser.add_argument('--path', {help: "path to build relative to input tree [default: '']"})
 parser.add_argument('--version', {
   action: 'version',

src/index.ts

@@ -231,9 +231,18 @@ export function expand(inputs: string[], outputPath: string, buildPath = ''): vo
     debug(`Processing file '${filePath}'`)
     if (templateRegex.exec(filePath)) {
       debug(`Expanding '${baseFile}' to '${outputFile}'`)
-      fs.writeFileSync(outputFile, expandFile(baseFile, filePath))
+      const output = expandFile(baseFile, filePath)
+      if (outputFile === '-') {
+        process.stdout.write(output)
+      } else {
+        fs.writeFileSync(outputFile, output)
+      }
     } else if (!noCopyRegex.exec(filePath)) {
-      fs.copyFileSync(filePath, outputFile)
+      if (outputFile === '-') {
+        process.stdout.write(fs.readFileSync(filePath))
+      } else {
+        fs.copyFileSync(filePath, outputFile)
+      }
     }
   }
 
@@ -244,6 +253,9 @@ export function expand(inputs: string[], outputPath: string, buildPath = ''): vo
     }
     if (isDirectory(dirent)) {
       const outputDir = getOutputPath(object)
+      if (outputDir === '-') {
+        throw new Error("cannot output multiple files to stdout ('-')")
+      }
       debug(`Entering directory '${object}'`)
       fs.ensureDirSync(outputDir)
       for (const childDirent of dirent) {

test/index.test.ts

@@ -28,40 +28,65 @@ function assertFileObjEqual(obj: string, expected: string) {
   )
 }
 
-function test(inputDirs: string[], expected: string, buildPath?: string) {
-  const outputDir = temporaryDirectory()
-  const outputObj = path.join(outputDir, 'output')
+function test(inputDirs: string[], expected: string, buildPath?: string, outputDir?: string) {
+  let tmpDir
+  let outputObj
+  if (outputDir === undefined) {
+    tmpDir = temporaryDirectory()
+    outputObj = path.join(tmpDir, 'output')
+  } else {
+    outputObj = outputDir
+  }
   if (buildPath !== undefined) {
     expand(inputDirs, outputObj, buildPath)
   } else {
     expand(inputDirs, outputObj)
   }
   assertFileObjEqual(outputObj, expected)
-  fs.rmSync(outputDir, {recursive: true})
+  if (tmpDir !== undefined) {
+    fs.rmSync(tmpDir, {recursive: true})
+  }
 }
 
-function failingTest(inputDirs: string[], expected: string, buildPath?: string) {
-  const outputDir = temporaryDirectory()
+function failingTest(
+  inputDirs: string[],
+  expected: string,
+  buildPath?: string,
+  outputDir?: string,
+) {
+  const expectedDir = temporaryDirectory()
   try {
-    test(inputDirs, outputDir, buildPath)
+    test(inputDirs, expectedDir, buildPath, outputDir)
   } catch (error: any) {
     // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
     expect(error.message).to.contain(expected)
     return
   } finally {
-    fs.rmSync(outputDir, {recursive: true})
+    fs.rmSync(expectedDir, {recursive: true})
   }
   throw new Error('test passed unexpectedly')
 }
 
-async function cliTest(args: string[], expected: string) {
-  const outputDir = temporaryDirectory()
-  const outputObj = path.join(outputDir, 'output')
+async function cliTest(args: string[], expected: string, outputDir?: string) {
+  let tmpDir
+  let outputObj
+  if (outputDir === undefined) {
+    tmpDir = temporaryDirectory()
+    outputObj = path.join(tmpDir, 'output')
+  } else {
+    outputObj = outputDir
+  }
   try {
-    await run(args.concat(outputObj))
-    assertFileObjEqual(outputObj, expected)
+    const res = await run(args.concat(outputObj))
+    if (tmpDir !== undefined) {
+      assertFileObjEqual(outputObj, expected)
+    } else {
+      expect(res.stdout).to.equal(fs.readFileSync(expected, 'utf-8'))
+    }
   } finally {
-    fs.rmSync(outputDir, {recursive: true})
+    if (tmpDir !== undefined) {
+      fs.rmSync(tmpDir, {recursive: true})
+    }
   }
 }
 
@@ -192,6 +217,10 @@ describe('nancy', function t() {
     failingTest([process.cwd()], 'missing close brace', 'missing-close-brace.nancy.txt')
   })
 
+  it('Trying to output multiple files to stdout should cause an error', async () => {
+    failingTest(['webpage-src'], 'cannot output multiple files to stdout', undefined, '-')
+  })
+
   // CLI tests
   it('--help should produce output', async () => {
     const proc = run(['--help'])
@@ -203,6 +232,10 @@ describe('nancy', function t() {
     await cliTest(['file-root-relative-include.nancy.txt'], 'file-root-relative-include-expected.txt')
   })
 
+  it('Output to stdout of a single file should work', async () => {
+    await cliTest(['file-root-relative-include.nancy.txt'], 'file-root-relative-include-expected.txt', '-')
+  })
+
   it('Missing command-line argument should cause an error', async () => {
     await failingCliTest([], 'the following arguments are required')
   })