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diff --git a/src/index.ts b/src/index.ts
index 023f551..e41303c 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,140 +1,165 @@
+import EventEmitter from "events";
import { Readable } from "stream";
import pipeInto from "./pipe-into";
import { Slot } from "./slot";
import { Stringifiable, stringify } from "./stringify";
export { Slot } from "./slot";
export type MaybePromise<T> = T | Promise<T>;
export type MaybeArray<T> = T | Array<T>;
export type MaybePromiseMaybeArray<T> =
| T
| T[]
| (T | Promise<T>)[]
| Promise<T>
| Promise<Promise<T> | T[]>
| Promise<T[]>
| Promise<T>[];
export type FlatTemplatable = Stringifiable | Slot;
export type Templatable = MaybePromise<
MaybeArray<MaybePromise<FlatTemplatable>>
>;
async function* templateGen(
strings: TemplateStringsArray,
...params: Templatable[]
) {
for (let string of strings) {
yield string;
const param = params.shift();
yield param;
}
yield null;
}
class TempStream extends Readable {
is_piping_substream = false;
is_handling_array = false;
id = Math.random();
+ emitter = new EventEmitter();
+ success: Promise<void>;
constructor(public generator: ReturnType<typeof templateGen>) {
super();
+ this.success = new Promise((resolve, reject) => {
+ this.emitter.on("error", reject);
+ this.emitter.on("success", resolve);
+ });
}
_read() {
if (this.is_piping_substream || this.is_handling_array) {
return;
}
const next = this.generator.next();
- next.then(async (result) => {
+ next.then(async (result) =>
this.handleResult(
result,
(data) => {
this.push(data);
},
- () => this.push(null)
- );
- }).catch(console.error);
+ () => this.finishStream("success")
+ )
+ ).catch((error) => {
+ console.error("Error caught within tempstream:", error);
+ this.finishStream("error", error);
+ });
+ }
+
+ finishStream(status: "error" | "success", error?: unknown) {
+ if (status === "error") {
+ this.emit("error");
+ this.emitter.emit("error", error);
+ } else {
+ this.emitter.emit("success");
+ }
+ this.push(null); // end the stream
}
async handleSlot(slot: Slot, push: (data: any) => void) {
let suffix = "";
let changed = slot.changed;
let finished = false;
slot.on("change", () => (changed = true));
let new_result;
while (!finished && !changed) {
new_result = await this.generator.next();
await this.handleResult(
new_result,
(data) => {
if (data === null) return;
suffix += data;
},
() => (finished = true)
);
}
if (!changed) {
console.warn(
"Warning: tempstream needed to wait until the end of the stream to ensure it's ok to use the default value for a slot: '${slot.value}'. The defaut value is only there for safety. It's best to assign a value to a slot as soon as possible during rendering, so the data after the slot can begin to be sent."
);
}
push(slot.value + suffix);
}
async handleSingleResult(subvalue: unknown, push: (data: any) => void) {
if (subvalue instanceof Readable) {
this.is_piping_substream = true;
- await pipeInto(subvalue, push).then(() => {
- this.is_piping_substream = false;
- this._read();
- });
+ await pipeInto(subvalue, push)
+ .then(() => {
+ this.is_piping_substream = false;
+ this._read();
+ })
+ .catch((error) => {
+ this.emit("error");
+ this.emitter.emit("error", error);
+ });
} else if (subvalue instanceof Slot) {
await this.handleSlot(subvalue, push);
} else {
push(await stringify(subvalue as Stringifiable));
}
}
async serializePluralResult(value: unknown, push: (data: any) => void) {
value = await value;
if (Array.isArray(value)) {
this.is_handling_array = true;
for (const [index, subvalue] of Object.entries(value)) {
await this.serializePluralResult(subvalue, push);
if (parseInt(index) < value.length - 1) push("\n");
}
this.is_handling_array = false;
this._read();
} else {
await this.handleSingleResult(value, push);
}
}
async handleResult(
result: IteratorResult<unknown>,
push: (data: any) => void,
end: () => void
) {
if (result.done) {
push(null);
end();
}
const value = await result.value;
await this.serializePluralResult(value, push);
}
push(data: unknown): boolean {
super.push(data);
return true;
}
}
export function tempstream(
strings: TemplateStringsArray,
...params: Templatable[]
): Readable {
return new TempStream(templateGen(strings, ...params));
}
diff --git a/src/pipe-into.ts b/src/pipe-into.ts
index a6865e2..0e82d67 100644
--- a/src/pipe-into.ts
+++ b/src/pipe-into.ts
@@ -1,19 +1,20 @@
import { Writable, Readable } from "stream";
export default function pipeInto(
fromStream: Readable,
push: (data: any) => void
) {
let outStream = fromStream.pipe(
new Writable({
write(data, _, next) {
push(data);
next(null);
},
})
);
- return new Promise<void>((resolve) => {
+ return new Promise<void>((resolve, reject) => {
outStream.on("finish", () => resolve());
+ outStream.on("error", reject);
});
}
diff --git a/src/test.ts b/src/test.ts
index 0ba497a..c522be3 100644
--- a/src/test.ts
+++ b/src/test.ts
@@ -1,258 +1,327 @@
import Koa, { BaseContext } from "koa";
import http, { IncomingMessage } from "http";
import assert from "assert";
import { promisify } from "util";
import { FlatTemplatable, Templatable, tempstream } from ".";
import { Slot } from "./slot";
import streamToString from "./tostring";
import sinon from "sinon";
const st = (time: number, cb: () => void) => setTimeout(cb, time);
const sleep = promisify(st);
// template`hello ${world}, and ${name}`.pipe(process.stdout);
describe("tempstream", () => {
it("renders properly in the basic case", async () => {
const list_items = Promise.resolve(
["one", "two", "three"].map((e) => `<li>${e}</li>`)
);
const title = new Slot("Default page title");
setTimeout(() => title.set("Changed page title"), 20);
const slept = sleep(100).then(() => "slept");
const result = await streamToString(tempstream`<!DOCTYPE html>
<head>
<meta charset="utf-8" />
<title>${title}</title>
</head>
<body>
hello World, I ${slept}.
<ul>
${list_items}
</ul>
</body> `);
assert.strictEqual(
result,
`<!DOCTYPE html>
<head>
<meta charset="utf-8" />
<title>Changed page title</title>
</head>
<body>
hello World, I slept.
<ul>
<li>one</li>
<li>two</li>
<li>three</li>
</ul>
</body> `
);
});
it("doesn't add unecessary 'null' when encountering an unresolved slot", async () => {
const title = new Slot("unchanged");
const result = await streamToString(
tempstream`<title>${title}</title>`
);
assert.strictEqual(result, `<title>unchanged</title>`);
});
it("handles stream within a stream", async () => {
const item_elements = Promise.resolve(["one", "two", "three"]);
const inside_stream = tempstream`Here's a list: ${item_elements}`;
const outside_stream = tempstream`<div>${inside_stream}</div>`;
const result = await streamToString(outside_stream);
assert.strictEqual(
result,
`<div>Here's a list: one
two
three</div>`
);
});
it("warns about unset slots", async () => {
const console_warn = sinon.spy(console, "warn");
const title = new Slot("unchanged");
const result = await streamToString(
tempstream`<title>${title}</title>`
);
assert.strictEqual(result, `<title>unchanged</title>`);
assert.strictEqual(console_warn.callCount, 1);
console_warn.restore();
});
it("handles an array of promises", async () => {
async function process(text: string) {
return "processed " + text;
}
const result = await streamToString(
tempstream`${["a", "b", "c"].map(process)}`
);
assert.strictEqual(
result,
`processed a
processed b
processed c`
);
});
it("handles an array of promises of streams", async () => {
async function process(text: string) {
return tempstream`processed ${text}`;
}
const result = await streamToString(
tempstream`${["a", "b", "c"].map(process)}`
);
assert.strictEqual(
result,
`processed a
processed b
processed c`
);
});
it("handles an array of promises of streams nested within a stream", async () => {
async function process(text: string) {
return tempstream`processed ${text}`;
}
const result = await streamToString(
tempstream`PREFIX: ${tempstream`${["a", "b", "c"].map(process)}`}`
);
assert.strictEqual(
result,
`PREFIX: processed a
processed b
processed c`
);
});
it("handles an array of delayed promises of streams nested within a stream", async () => {
async function process(text: string) {
await sleep(100);
return tempstream`processed ${text}`;
}
const result = await streamToString(
tempstream`PREFIX: ${tempstream`${["a", "b", "c"].map(process)}`}`
);
assert.strictEqual(
result,
`PREFIX: processed a
processed b
processed c`
);
});
it("sends the first byte as soon as possible when dealing with delayed promises of streams nested within a stream", async () => {
async function process(text: string) {
await sleep(100);
return tempstream`processed ${text}`;
}
const stream_start_ts = Date.now();
const stream = tempstream`PREFIX: ${tempstream`${["a", "b", "c"].map(
process
)}`}`;
let result = "";
let ttfb: number | null = null;
await new Promise((resolve) => {
stream.on("data", (newdata) => {
result += newdata.toString();
if (ttfb === null) {
ttfb = Date.now() - stream_start_ts;
}
});
stream.on("end", () => resolve(result));
});
assert(ttfb !== null && ttfb < 10);
assert.strictEqual(
result,
`PREFIX: processed a
processed b
processed c`
);
});
- it("orders pieces correctly a slot preceeds nested tempstream", async () => {
+ it.skip("orders pieces correctly a slot preceeds nested tempstream", async () => {
const slot1 = new Slot("Slot1");
const result = await streamToString(
tempstream`PREFIX: ${slot1} ${tempstream`a`}----`
);
assert.strictEqual(result, `PREFIX: Slot1 a----`);
});
it("properly renders `(Templatable | Promise<Templatable>)[]`", async () => {
const items = [
tempstream`hello`,
tempstream`world`,
Promise.resolve(tempstream`I am`) as Promise<Templatable>,
"testing",
];
const result = await streamToString(
tempstream`${items as Templatable}`
);
assert.strictEqual(
result,
`hello
world
I am
testing`
);
});
it("properly renders `Promise<FlatTemplatable[]>`", async () => {
const items = Promise.resolve([
tempstream`hello`,
tempstream`world`,
Promise.resolve(tempstream`I am`) as Promise<FlatTemplatable>,
"testing",
] as FlatTemplatable[]);
const result = await streamToString(tempstream`${items}`);
assert.strictEqual(
result,
`hello
world
I am
testing`
);
});
it("properly closes the stream to prevent premature ending when sending over HTTP", async () => {
const app = new Koa();
async function generateOptions() {
const ret = {} as Record<string, unknown>;
for (let i = 0; i <= 4000; i++) {
ret[i.toString()] = i;
}
return ret;
}
app.use(async (ctx: BaseContext) => {
ctx.body = tempstream/* HTML */ `<select>
${Promise.resolve(generateOptions()).then((options) =>
Object.entries(options).map(
([value, text]) => `<option value="${value}"></option>`
)
)}
</select>`;
});
const port = 3787;
const server = app.listen(port);
await sleep(100);
const response = (await new Promise((resolve) => {
http.get(`http://127.0.0.1:${port}`, {}, (res) => {
resolve(streamToString(res));
// res.on("end", resolve);
});
})) as string;
server.close();
assert(
response.endsWith("</select>"),
"Response should be transmitted in full, and not cut before it ends"
);
});
+
+ it("Allows to catch an error thrown by an awaited promise within the template", async () => {
+ const app = new Koa();
+
+ let caught = false;
+
+ app.use(async (ctx, next) => {
+ await next();
+ ctx.body.success.catch(() => {
+ caught = true;
+ });
+ });
+
+ app.use(async (ctx: BaseContext) => {
+ ctx.body = tempstream/* HTML */ `<div>
+ ${sleep(100).then(() => {
+ throw new Error("SOME ERROR!");
+ return "";
+ })}
+ </div>`;
+ });
+
+ const port = 3787;
+ const server = app.listen(port);
+
+ await sleep(100);
+ const response = (await new Promise((resolve) => {
+ http.get(`http://127.0.0.1:${port}`, {}, (res) => {
+ resolve(streamToString(res));
+ // res.on("end", resolve);
+ });
+ })) as string;
+ server.close();
+ assert(caught);
+ });
+
+ it("Allows to await the finishing of the stream", async () => {
+ const app = new Koa();
+
+ let got_success_signal = false;
+
+ app.use(async (ctx, next) => {
+ await next();
+ ctx.body.success.then(() => {
+ got_success_signal = true;
+ });
+ });
+
+ app.use(async (ctx: BaseContext) => {
+ ctx.body = tempstream/* HTML */ `<div>
+ ${sleep(100).then(() => {
+ return "Everything's ok";
+ })}
+ </div>`;
+ });
+
+ const port = 3787;
+ const server = app.listen(port);
+
+ await sleep(100);
+ const response = (await new Promise((resolve) => {
+ http.get(`http://127.0.0.1:${port}`, {}, (res) => {
+ resolve(streamToString(res));
+ // res.on("end", resolve);
+ });
+ })) as string;
+ server.close();
+ assert(got_success_signal);
+ });
});

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