src/hero.mjs: Add simplified implementation of `makePipeReader()`

There are a few limitations of the current approach that I didn't
figure out how to solve yet:

1. when stopping the server, mainly for shutting down the Node.js
   process when running the tests, we need to open and close the pipe in
   write mode at least once, otherwise it hangs forever.  After opening
   and closing it, the "autoClose" functionality of the
   `fs.createReadStream()` kicks in, and it closes, otherwise the test
   hangs forever as Node.js still has open handles.  That's why the
   `server.close()` function has a gratuitous call to
   `fs.createWriteStream(pipe).end()`: so that when stopping the server,
   the pipe is always closed at least once;
2. when actually running the application, if one tries an IPC command
   like:

     $ echo '{ "action": "config-dump" }' > web.pipe

   It works, but only for the first time.  As this shell line opened the
   pipe, wrote to it and then closed it, the reader that
   `makePipeReader()` constructed closed, but didn't open it again.  So
   when running the exact same IPC command for a second time, the shell
   hangs, as there is no process on the other side listening for the
   command and consuming the pipe.

Shortcoming nº 2 is much more important to be solved, as we can live
with shortcoming nª 1 for some time.  Both are to be fixed in the near
future.

2 files changed, 26 insertions, 2 deletions

diff --git a/src/hero.mjs b/src/hero.mjs
index 699e426..bcc4fdb 100644
--- a/src/hero.mjs
+++ b/src/hero.mjs
@@ -363,7 +363,7 @@ export const makePipeReaderFn = ({
 	lineFn: lineHandler
 }) => path => {
 	mkfifo(path);
-	// TODO
+	fs.createReadStream(path, "UTF-8").on("data", makeLineEmitter(lineFn));
 };
 
 export const makePipeReader = makePipeReaderFn();
@@ -397,7 +397,10 @@ export const promisifyServer = (name, serverHandle, socket, pipe) => ({
 		rmIf(socket);
 		return serverHandle.listen(socket, ...args)
 	}),
-	close:  util.promisify((...args) => serverHandle.close(...args)),
+	close:  util.promisify((...args) => {
+		fs.createWriteStream(pipe).end();
+		return serverHandle.close(...args);
+	}),
 	events: serverHandle,
 });
 
diff --git a/tests/js/hero.mjs b/tests/js/hero.mjs
index 67cf690..14d9a07 100644
--- a/tests/js/hero.mjs
+++ b/tests/js/hero.mjs
@@ -1378,6 +1378,12 @@ const test_makePipeReaderFn = async t => {
 		const lines = [];
 		const lineFn = x => lines.push(x);
 		const makePipeReader = makePipeReaderFn({ lineFn: null });
+
+		rmIf(path);
+		makePipeReader(path);
+		fs.createWriteStream(path).end();
+
+		assert.deepEqual(lines, []);
 	});
 
 	await t.test("closing on pipe EOF reopens", async () => {
@@ -1385,6 +1391,21 @@ const test_makePipeReaderFn = async t => {
 		const lines = [];
 		const lineFn = x => lines.push(x);
 		const makePipeReader = makePipeReaderFn({ lineFn });
+
+		rmIf(path);
+		makePipeReader(path);
+		const writer = fs.createWriteStream(path);
+		writer.end("first\nsecond\nthird\n");
+		return new Promise((resolve, reject) => {
+			writer.close(() => {
+				assert.deepEqual(lines, [
+					"first",
+					"second",
+					"third",
+				]);
+				resolve();
+			});
+		});
 	});
 };