fix dtypes not used on csv parse

Author: risenW

.gitignore

@@ -3,3 +3,5 @@ node_modules
 test/fixtures/*
 test/samples/*
 *.xlsx
+
+testsss

src/danfojs-base/io/browser/io.csv.ts

@@ -48,14 +48,16 @@ import Papa from 'papaparse'
  */
 const $readCSV = async (file: any, options?: CsvInputOptionsBrowser): Promise<DataFrame> => {
   const frameConfig = options?.frameConfig || {}
+  const hasStringType = frameConfig.dtypes?.includes("string")
 
   return new Promise((resolve, reject) => {
     let hasError = false;
 
     Papa.parse(file, {
       header: true,
-      dynamicTyping: true,
+      dynamicTyping: !hasStringType,
       skipEmptyLines: 'greedy',
+      delimiter: ",",
       ...options,
       error: (error) => {
         hasError = true;
@@ -108,12 +110,13 @@ const $streamCSV = async (file: string, callback: (df: DataFrame) => void, optio
   return new Promise((resolve, reject) => {
     let count = 0
     let hasError = false;
-
+    const hasStringType = frameConfig.dtypes?.includes("string")
     Papa.parse(file, {
-      ...options,
-      dynamicTyping: true,
       header: true,
       download: true,
+      dynamicTyping: !hasStringType,
+      delimiter: ",",
+      ...options,
       step: results => {
         if (hasError) return;
         try {

src/danfojs-base/io/node/io.csv.ts

@@ -50,14 +50,16 @@ import fs from 'fs'
  */
 const $readCSV = async (filePath: string, options?: CsvInputOptionsNode): Promise<DataFrame> => {
   const frameConfig = options?.frameConfig || {}
+  const hasStringType = frameConfig.dtypes?.includes("string")
 
   if (filePath.startsWith("http") || filePath.startsWith("https")) {
     return new Promise((resolve, reject) => {
       let hasError = false;
       const optionsWithDefaults = {
         header: true,
-        dynamicTyping: true,
+        dynamicTyping: !hasStringType,
         skipEmptyLines: 'greedy',
+        delimiter: ",",
         ...options,
       }
 
@@ -116,7 +118,8 @@ const $readCSV = async (filePath: string, options?: CsvInputOptionsNode): Promis
 
         Papa.parse(fileStream, {
           header: true,
-          dynamicTyping: true,
+          dynamicTyping: !hasStringType,
+          delimiter: ",",
           ...options,
           error: (error) => {
             hasError = true;

src/danfojs-browser/tests/io/csv.reader.test.js

@@ -97,6 +97,41 @@ describe("readCSV", function () {
       assert.ok(error instanceof Error);
     }
   });
+
+  it("Preserves leading zeros when dtype is string", async function () {
+    // Create a CSV file with leading zeros
+    const csvContent = "codes\n012345\n001234";
+    const file = new File([ csvContent ], "leading_zeros.csv", { type: "text/csv" });
+
+    const df = await dfd.readCSV(file, {
+      frameConfig: {
+        dtypes: [ "string" ]
+      }
+    });
+
+    assert.deepEqual(df.values, [ [ "012345" ], [ "001234" ] ]);
+    assert.deepEqual(df.dtypes, [ "string" ]);
+
+    // Verify the values are actually strings
+    const jsonData = dfd.toJSON(df);
+    assert.deepEqual(jsonData, [ { codes: "012345" }, { codes: "001234" } ]);
+  });
+
+  it("Converts to numbers when dtype is not string", async function () {
+    // Create a CSV file with leading zeros
+    const csvContent = "codes\n012345\n001234";
+    const file = new File([ csvContent ], "leading_zeros.csv", { type: "text/csv" });
+
+    const df = await dfd.readCSV(file); // default behavior without string dtype
+
+    // Values should be converted to numbers
+    assert.deepEqual(df.values, [ [ 12345 ], [ 1234 ] ]);
+    assert.deepEqual(df.dtypes, [ "int32" ]);
+
+    // Verify JSON output
+    const jsonData = dfd.toJSON(df);
+    assert.deepEqual(jsonData, [ { codes: 12345 }, { codes: 1234 } ]);
+  });
 });
 
 // describe("streamCSV", function () {

src/danfojs-node/test/io/csv.reader.test.ts

@@ -2,7 +2,7 @@ import path from "path";
 import chai, { assert, expect } from "chai";
 import { describe, it } from "mocha";
 import chaiAsPromised from "chai-as-promised";
-import { DataFrame, readCSV, Series, streamCSV, toCSV } from "../../dist/danfojs-node/src";
+import { DataFrame, readCSV, Series, streamCSV, toCSV, toJSON } from "../../dist/danfojs-node/src";
 import fs from 'fs';
 import process from 'process';
 
@@ -112,6 +112,59 @@ describe("readCSV", function () {
     const filePath = path.join(testSamplesDir, "invalid.csv");
     await expect(readCSV(filePath)).to.be.rejectedWith("ENOENT: no such file or directory");
   });
+
+  it("Preserves leading zeros when dtype is string", async function () {
+    const filePath = path.join(testSamplesDir, "leading_zeros.csv");
+    // Create test CSV file
+    fs.writeFileSync(filePath, "codes\n012345\n001234");
+
+    try {
+      const df = await readCSV(filePath, {
+        frameConfig: {
+          dtypes: ["string"]
+        }
+      });
+
+      assert.deepEqual(df.values, [["012345"], ["001234"]]);
+      assert.deepEqual(df.dtypes, ["string"]);
+
+      // Verify the values are actually strings
+      const jsonData = toJSON(df);
+      assert.deepEqual(jsonData, [{ codes: "012345" }, { codes: "001234" }]);
+
+      // Clean up
+      fs.unlinkSync(filePath);
+    } catch (error) {
+      // Clean up even if test fails
+      fs.unlinkSync(filePath);
+      throw error;
+    }
+  });
+
+  it("Converts to numbers when dtype is not string", async function () {
+    const filePath = path.join(testSamplesDir, "leading_zeros.csv");
+    // Create test CSV file
+    fs.writeFileSync(filePath, "codes\n012345\n001234");
+
+    try {
+      const df = await readCSV(filePath); // default behavior without string dtype
+
+      // Values should be converted to numbers
+      assert.deepEqual(df.values, [[12345], [1234]]);
+      assert.deepEqual(df.dtypes, ["int32"]);
+
+      // Verify JSON output
+      const jsonData = toJSON(df);
+      assert.deepEqual(jsonData, [{ codes: 12345 }, { codes: 1234 }]);
+
+      // Clean up
+      fs.unlinkSync(filePath);
+    } catch (error) {
+      // Clean up even if test fails
+      fs.unlinkSync(filePath);
+      throw error;
+    }
+  });
 });
 
 describe("streamCSV", function () {