fix(csv-generate): make numeric zero seeds deterministic

packages/csv-generate/lib/api/normalize_options.js

@@ -43,6 +43,10 @@ const normalize_options = (opts) => {
       options[k] = dft[k];
     }
   }
+  // Zero is a fixed point of the seeded recurrence; use the existing initial seed.
+  if (options.seed === 0) {
+    options.seed = 1;
+  }
   // Default values
   if (options.eof === true) {
     options.eof = options.rowDelimiter;

packages/csv-generate/test/options.seed.js

@@ -1,5 +1,7 @@
 import "should";
+import { spawnSync } from "node:child_process";
 import { generate } from "../lib/index.js";
+import { generate as generateSync } from "../lib/sync.js";
 import { random } from "../lib/api/random.js";
 
 describe("Option `seed`", function () {
@@ -14,6 +16,78 @@ describe("Option `seed`", function () {
     });
   });
 
+  describe("with zero seed", function () {
+    it("generate repeatable records synchronously", function () {
+      const options = {
+        seed: 0,
+        columns: ["ascii", "ascii"],
+        length: 3,
+        objectMode: true,
+      };
+      const records = generateSync(options);
+      records.should.eql(generateSync(options));
+      records
+        .every((record) => record.every((word) => word.length > 0))
+        .should.be.true();
+    });
+
+    it("generate repeatable records with a callback", function (next) {
+      const options = {
+        seed: 0,
+        columns: ["ascii", "ascii"],
+        length: 3,
+        objectMode: true,
+      };
+      generate(options, (err, records) => {
+        if (err) return next(err);
+        records.should.eql(generateSync(options));
+        records
+          .every((record) => record.every((word) => word.length > 0))
+          .should.be.true();
+        next();
+      });
+    });
+
+    it("generate repeatable records as a stream", async function () {
+      const options = {
+        seed: 0,
+        columns: ["ascii", "ascii"],
+        length: 3,
+        objectMode: true,
+      };
+      const records = [];
+      for await (const record of generate(options)) records.push(record);
+      records.should.eql(generateSync(options));
+      records
+        .every((record) => record.every((word) => word.length > 0))
+        .should.be.true();
+    });
+
+    it("yield the first record from an unbounded object stream", function () {
+      const moduleUrl = new URL("../lib/index.js", import.meta.url).href;
+      const result = spawnSync(
+        process.execPath,
+        [
+          "--max-old-space-size=32",
+          "--input-type=module",
+          "-e",
+          `import { generate } from ${JSON.stringify(moduleUrl)};
+         const generator = generate({ seed: 0, objectMode: true });
+         generator.once("data", (record) => {
+           console.log(JSON.stringify(record));
+           generator.destroy();
+         });`,
+        ],
+        { timeout: 10000, encoding: "utf8" },
+      );
+      if (result.error) throw result.error;
+      result.status.should.equal(0, result.stderr);
+      const record = JSON.parse(result.stdout);
+      record.should.have.length(8);
+      record.every((word) => word.length > 0).should.be.true();
+    });
+  });
+
   describe("with seed", function () {
     it("generate same values", function () {
       random(generate({ seed: 1 }).options).should.equal(