fix(csv-parse): normalized columns with auto-detected bom (fix #460)

wdavidw · wdavidw · commit 4abcc445ccdd · 2025-07-16T19:51:23.000+02:00
diff --git a/packages/csv-parse/lib/api/index.js b/packages/csv-parse/lib/api/index.js
@@ -115,10 +115,14 @@ const transform = function (original_options = {}) {
               this.state.bufBytesStart += bomLength;
               buf = buf.slice(bomLength);
               // Renormalize original options with the new encoding
-              this.options = normalize_options({
+              const options = normalize_options({
                 ...this.original_options,
                 encoding: encoding,
               });
+              // Properties are merged with the existing options instance
+              for (const key in options) {
+                this.options[key] = options[key];
+              }
               // Options will re-evaluate the Buffer with the new encoding
               ({ comment, escape, quote } = this.options);
               break;
diff --git a/packages/csv-parse/lib/api/normalize_options.js b/packages/csv-parse/lib/api/normalize_options.js
@@ -650,7 +650,7 @@ const normalize_options = function (opts) {
   // Normalize option `to`
   if (options.to === undefined || options.to === null) {
     options.to = -1;
-  } else {
+  } else if (options.to !== -1) {
     if (typeof options.to === "string" && /\d+/.test(options.to)) {
       options.to = parseInt(options.to);
     }
@@ -669,7 +669,7 @@ const normalize_options = function (opts) {
   // Normalize option `to_line`
   if (options.to_line === undefined || options.to_line === null) {
     options.to_line = -1;
-  } else {
+  } else if (options.to_line !== -1) {
     if (typeof options.to_line === "string" && /\d+/.test(options.to_line)) {
       options.to_line = parseInt(options.to_line);
     }
diff --git a/packages/csv-parse/test/option.bom.ts b/packages/csv-parse/test/option.bom.ts
@@ -127,4 +127,18 @@ describe("Option `bom`", function () {
     parser.write(Buffer.from([239, 187]));
     parser.end();
   });
+
+  it("options instance is updated and not re-created (see #460)", async function () {
+    // https://github.com/adaltas/node-csv/issues/460
+    const parser = parse({
+      columns: true,
+      bom: true,
+      from_line: 2,
+    });
+    parser.write(Buffer.from("\ufeffa,b\n"));
+    parser.write(Buffer.from("1,2\n"));
+    parser.write(Buffer.from("3,4\n"));
+    parser.end();
+    parser.options?.columns.should.eql([{ name: "1" }, { name: "2" }]);
+  });
 });
diff --git a/packages/csv-parse/test/option.to.ts b/packages/csv-parse/test/option.to.ts
@@ -8,9 +8,9 @@ describe("Option `to`", function () {
     parse("", { to: "10" }, () => {});
     parse("", { to: null }, () => {});
     (() => {
-      parse("", { to: -1 }, () => {});
+      parse("", { to: -2 }, () => {});
     }).should.throw(
-      "Invalid Option: to must be a positive integer greater than 0, got -1",
+      "Invalid Option: to must be a positive integer greater than 0, got -2",
     );
     (() => {
       parse("", { to: 0 }, () => {});
diff --git a/packages/csv-parse/test/option.to_line.ts b/packages/csv-parse/test/option.to_line.ts
@@ -9,9 +9,9 @@ describe("Option `to_line`", function () {
     parse("", { to_line: null }, () => {});
     parse("", { to_line: undefined }, () => {});
     (() => {
-      parse("", { to_line: -1 }, () => {});
+      parse("", { to_line: -2 }, () => {});
     }).should.throw(
-      "Invalid Option: to_line must be a positive integer greater than 0, got -1",
+      "Invalid Option: to_line must be a positive integer greater than 0, got -2",
     );
     (() => {
       parse("", { to_line: 0 }, () => {});
