fix(data-grid): apply improvements from code review findings

[sadmann7]

Summary

Apply fixes and improvements discovered during code review and testing. These changes address edge cases and performance issues in the data grid implementation.

Changes

1. Fix prevIsEditingRef initialization

• Initialize to false instead of isEditing in ShortTextCell, NumberCell, and UrlCell
• Why: When a cell mounts already in edit mode (e.g., via keyboard navigation), the ref needs to start as false so the focus/selection logic runs correctly on first render

2. Preserve undefined/null entries in onDataUpdate

• Explicitly preserve undefined/null values when building newData array
• Why: Maintains correct array structure and indices, prevents data corruption if source data intentionally has gaps

3. Optimize onRowSelect implementation

• Use single findIndex instead of findIndex + array access
• Use rowId directly instead of getting currentRow.id
• Handle edge case where last clicked row was filtered out
• Why: Cleaner code, better performance on large tables

4. Filter non-navigable columns from copy operation

• Skip checkbox/select columns when building TSV data for clipboard
• Why: Prevents column misalignment when pasting, users don't want selection state in clipboard

5. Simplify cell persistence logic

• Remove unnecessary fallback chains in data update loop
• Use currentData.length instead of tableRowCount
• Why: Clearer code, matches original fix intent

Testing

These changes address edge cases found through:

• Static code analysis
• Manual testing with filtering, sorting, and editing
• Edge case testing (cells mounting in edit mode, filtered rows)

Risk Assessment

Low Risk - All changes are refinements to existing fixes that have already been deployed. They address edge cases and improve code quality without changing core behavior.

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Project	Deployment	Actions	Updated (UTC)
tablecn	Ready	Preview, Comment	Feb 25, 2026 8:12am

[Copilot]

Pull request overview

This PR completely rewrites the TSV (Tab-Separated Values) parsing implementation used for clipboard paste operations in the data grid. The function is renamed from parseTsv to parseTsvText and changes from a tab-counting approach to a character-by-character parser that supports RFC 4180 CSV/TSV format with quoted fields.

Changes:

• Replaced parseTsv with parseTsvText implementing RFC 4180-style parsing with quote handling
• Removed the fallbackColumnCount parameter, allowing variable-width rows
• Added support for escaped quotes ("" within quoted fields) and mixed line endings

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 7 comments.

File	Description
src/lib/data-grid.ts	Completely rewrites the TSV parsing function to support quoted fields and RFC 4180 format
src/hooks/use-data-grid.ts	Updates the import and function call to use the renamed parseTsvText function

Note: The PR description mentions 5 different types of changes (cell ref fixes, onDataUpdate improvements, onRowSelect optimization, etc.), but none of these changes are present in the actual diff. The only changes are to the TSV parsing function.

Comments suppressed due to low confidence (2)

src/lib/data-grid.ts:309

• The function uses string concatenation (currentField += char) in a character-by-character loop. For very large clipboard contents (e.g., thousands of rows), this could cause performance issues due to string immutability in JavaScript creating a new string object on each concatenation. Consider using an array to collect characters and joining them at the end of each field (e.g., currentFieldChars.push(char) then currentField = currentFieldChars.join("")), or document the expected size limitations of clipboard data.

  while (i < text.length) {
    const char = text[i];
    const nextChar = text[i + 1];

    if (inQuotes) {
      if (char === '"' && nextChar === '"') {
        currentField += '"';
        i += 2;
      } else if (char === '"') {
        inQuotes = false;
        i++;
      } else {
        currentField += char;
        i++;
      }
    } else {
      if (char === '"' && currentField === "") {
        inQuotes = true;
        i++;
      } else if (char === "\t") {
        currentRow.push(currentField);
        currentField = "";
        i++;
      } else if (char === "\n") {
        currentRow.push(currentField);
        if (currentRow.length > 1 || currentRow.some((f) => f.length > 0)) {
          rows.push(currentRow);
        }
        currentRow = [];
        currentField = "";
        i++;
      } else if (char === "\r" && nextChar === "\n") {
        currentRow.push(currentField);
        if (currentRow.length > 1 || currentRow.some((f) => f.length > 0)) {
          rows.push(currentRow);
        }
        currentRow = [];
        currentField = "";
        i += 2;
      } else {
        currentField += char;
        i++;
      }
    }

src/lib/data-grid.ts:309

• The function handles \n (Unix) and \r\n (Windows) line endings, but does not handle standalone \r (legacy Mac OS 9 line endings). If a user pastes data with \r line endings, each \r character will be treated as regular content and included in the field value, resulting in incorrect parsing. While Mac OS 9 line endings are rare today, consider either adding support for them or documenting that only Unix and Windows line endings are supported.

      } else if (char === "\n") {
        currentRow.push(currentField);
        if (currentRow.length > 1 || currentRow.some((f) => f.length > 0)) {
          rows.push(currentRow);
        }
        currentRow = [];
        currentField = "";
        i++;
      } else if (char === "\r" && nextChar === "\n") {
        currentRow.push(currentField);
        if (currentRow.length > 1 || currentRow.some((f) => f.length > 0)) {
          rows.push(currentRow);
        }
        currentRow = [];
        currentField = "";
        i += 2;
      } else {
        currentField += char;
        i++;
      }
    }

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (2)

src/lib/data-grid.ts:302

• The condition for skipping empty rows (currentRow.length > 1 || currentRow.some((f) => f.length > 0)) may inadvertently skip valid single-column rows that contain only empty strings. If a TSV has a single column and that column's value is an empty string for a particular row, that row will be skipped. Consider whether this behavior is intentional. If single-column empty rows should be preserved, the condition should be adjusted.

          if (currentRow.length > 1 || currentRow.some((f) => f.length > 0)) {
            rows.push(currentRow);

src/lib/data-grid.ts:318

• The quoted field parser only handles Windows line endings (\r\n) but not standalone carriage returns (\r) that were used in classic Mac OS. If pasted data contains standalone \r characters, they will be treated as regular field content rather than row delimiters. Consider adding a case to handle standalone \r for better compatibility, or document this limitation.

        } else if (char === "\r" && nextChar === "\n") {
          currentRow.push(currentField);
          if (currentRow.length > 1 || currentRow.some((f) => f.length > 0)) {
            rows.push(currentRow);
          }
          currentRow = [];
          currentField = "";
          i += 2;
        } else {
          currentField += char;
          i++;
        }

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