I’m working on duplicating tables between Google Docs using the API and running into issues when the source tables have header rows. My initial approach worked fine for regular tables, but when I try to preserve header formatting, I get an error. Here’s what I’m attempting:
The API responds with: modifyTableRowProperties: Unallowed field: tableHeader
Interestingly, if I use "fields": "*" instead, the operation completes but the header formatting gets lost in the process. Other row style properties work without problems when specified explicitly in the fields parameter. Has anyone encountered this limitation before? Is there a workaround to properly copy header row formatting?
Had this exact problem last month building a document templating system. You can’t modify tableHeader with modifyTableRowProperties - it’s controlled at the table level, not row level. I used insertTable with the tableRows property instead, setting tableHeader: true for specific rows when creating the table. For existing tables, I had to delete and recreate them with the right header setup. It’s annoying but that’s the only way I found to make header formatting work reliably. Google’s API docs don’t mention this limitation anywhere, which made debugging a pain.
The tableHeader property works differently than other table formatting in the Google Docs API. I ran into this with a corporate reporting tool - turns out header rows need table-level operations, not individual row changes. Here’s what worked: use insertTableRow with header properties set from the start, then copy your content row by row from the source table. You’ll extract the existing data first, delete the original table, and rebuild it with proper headers. Takes more API calls but keeps headers formatted correctly and preserves your content structure. Works consistently across different document types.
You’re encountering an error when trying to modify the header row formatting of a table in a Google Doc using the modifyTableRowProperties API method. The API returns the error modifyTableRowProperties: Unallowed field: tableHeader, even though other row style properties work correctly. Using "fields": "*" completes the operation, but it loses the header formatting.
Understanding the “Why” (The Root Cause):
The tableHeader property in the Google Docs API isn’t directly modifiable using modifyTableRowProperties at the row level. This property is managed at the table level, not the individual row level. Attempting to modify it using modifyTableRowProperties results in the error you’re seeing. While the "fields": "*" workaround completes the operation, it overwrites the header formatting because the API doesn’t allow selective modification of tableHeader within a row’s properties.
Step-by-Step Guide:
Delete and Recreate the Table: The most reliable solution is to delete the existing table and recreate it with the correct header formatting from the outset. This ensures the tableHeader property is correctly set at the table creation stage.
Extract Data: Before deleting the table, extract the data from all rows, including the header row, preserving any formatting within individual cells. You can achieve this by iterating through each cell in the table and using the copy() method to preserve formatting. Store this extracted data in a suitable data structure (e.g., a list of lists or an array of objects).
Insert a New Table: Use the insertTable method to create a new table with the desired number of rows and columns. In the initial creation of the table, use the tableRows property to specify the properties of each row, explicitly setting tableHeader: true for the first row (header row).
Populate the New Table: Iterate through the extracted data and populate the cells of the newly created table using the setTable method. Use the previously stored formatting information (obtained in Step 2) to ensure your content maintains the same formatting in the new table.
Remove the Old Table: After successfully populating the new table, remove the original table from the document.
Example Code (JavaScript):
function copyTableWithHeader() {
// ... (Code to get source and target tables) ...
const sourceTable = DocumentApp.getActiveDocument().getBody().getTables()[0];
const numRows = sourceTable.getNumRows();
const numCols = sourceTable.getNumColumns();
const data = [];
for (let i = 0; i < numRows; i++) {
const row = [];
for (let j = 0; j < numCols; j++) {
const cell = sourceTable.getRow(i).getCell(j);
row.push({ content: cell.getText(), formatting: cell.copy() }); // Preserve formatting
}
data.push(row);
}
sourceTable.removeFromParent(); // Remove original table
const newTable = DocumentApp.getActiveDocument().getBody().insertTable(numRows, numCols);
// Set header row properties on the first row
newTable.getRow(0).setAttributes({tableHeader: true});
for (let i = 0; i < numRows; i++) {
for (let j = 0; j < numCols; j++) {
const cell = newTable.getRow(i).getCell(j);
cell.appendParagraph(data[i][j].content);
cell.setAttributes(data[i][j].formatting);
}
}
}
Common Pitfalls & What to Check Next:
Index Errors: Double-check your row and column indices when accessing cells. Remember that array indices start at 0.
Table Selection: Make sure you’re correctly selecting the source and target tables. Use getBody().getTables() and carefully examine the array indices if there are multiple tables in the document.
Formatting Preservation: The copy() method generally preserves formatting, but very complex formatting might require more manual handling. Test thoroughly after making changes.
Error Handling: Add error handling to gracefully manage situations where tables might not be found or other unexpected errors occur.
Still running into issues? Share your (sanitized) config files, the exact command you ran, and any other relevant details. The community is here to help!
google hasn’t fixed this bug yet. you can’t update the tableHeader field directly through modifyTableRowProperties since it’s protected. the only workaround i’ve found is creating a new table with insertTable (configure headers first), then manually copy over your cell data. it’s tedious but it’s the only way that actually preserves header styling.
Understanding the “Why” (The Root Cause):
Step-by-Step Guide:
Common Pitfalls & What to Check Next:
Still running into issues? Share your (sanitized) config files, the exact command you ran, and any other relevant details. The community is here to help!