How can I fix the [["Mashup Exception"]] error*** in Power Query?

Microsoft Fabric is a unified data platform that combines various data services, including Power BI, data engineering, and more, into a single environment. It is designed to simplify and streamline the process of data management, analytics, and machine learning. One of the key components of Microsoft Fabric is Power Query, which allows users to retrieve, transform, and shape data from various sources, including SharePoint, SQL databases, Excel, and more.

In this article, we will walk through the process of resolving a common error encountered in Power Query while accessing a SharePoint folder in Microsoft Fabric Dataflows. This error may appear when attempting to retrieve data from a SharePoint folder using the SharePoint.Contents() function. We will explore the root cause of the issue and provide troubleshooting steps, along with a detailed FAQ section to help new users understand the problem and how to resolve it.

Background

Overview of Microsoft Fabric Dataflows

In Microsoft Fabric, Dataflows are a key component of the data integration process. They allow users to create data transformation pipelines where data can be extracted from various sources, transformed, and then loaded into data storage or analytical environments for further processing. Power Query is often used in dataflows to perform data extraction, transformation, and load (ETL) tasks.

When working with SharePoint folders in a dataflow, the SharePoint.Contents function is commonly used to access files and lists stored on SharePoint. This function returns metadata about the contents of the specified SharePoint folder, which can then be further processed or transformed to meet the needs of your data pipeline.

The Error Encountered

The specific error message you're encountering while working with SharePoint folders in Power Query is as follows:

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SharePoint list: Error Code: Mashup Exception Expression Error, Error Details: Couldn't refresh the entity because of an issue with the mashup document MashupException.Error: Expression.Error: Failed to insert a table., InnerException: We cannot convert a value of type Table to type Text., Underlying error: We cannot convert a value of type Table to type Text. Details: Reason = Expression.Error;Microsoft.Data.Mashup.ErrorCode = Lakehouse036;Message = We cannot convert a value of type #{0} to type #{1}.;Message.Parameters = {"Table", "Text"};ErrorCode = 10276;Microsoft.Data.Mashup.Error.Context = User

This error suggests that there is a mismatch between the expected data type and the actual data type being passed through the query. Specifically, the issue arises when a Table data type is being incorrectly interpreted as a Text data type.

Let's break down the issue, potential causes, and how to resolve it.

Understanding the Error

Error Analysis

The error can be divided into several key parts:

Mashup Exception: The error is related to the mashup document, which is the file that defines the steps for data transformation in Power Query.

Expression.Error: Failed to insert a table: This suggests that Power Query encountered a problem while trying to process or insert a table into the dataflow.

Type Mismatch: The critical part of the error message is: "We cannot convert a value of type Table to type Text." This indicates that the query is trying to use a Table data type where Text is expected, which is causing the failure.

Underlying Error Details: The error code 10276 and the context message "We cannot convert a value of type Table to type Text" provide further insight into the issue, highlighting that the data type mismatch is the root cause.

Root Causes of the Error

There are several potential causes for this issue:

Incorrect Data Transformation Steps: In Power Query, transformations like filtering, expanding, or merging tables require specific data types. If one of these transformations is applied incorrectly (e.g., trying to merge a table with text data), the error can occur.

Inconsistent Data Types: If the SharePoint folder contains different types of files (such as CSV files, Word documents, or Excel sheets), Power Query may encounter difficulties interpreting the metadata or contents of these files. For example, if Power Query expects CSV files but encounters a non-CSV file, it could cause a data type mismatch.

File Structure Issues: The contents of the CSV files themselves may have an irregular structure, such as mismatched columns or missing values. This could cause Power Query to misinterpret the file as a different data type.

API Version Compatibility: The SharePoint API version you are using might not fully support the operation you're trying to perform. For example, using an older API version may limit the functionality or compatibility with certain file types.

Troubleshooting and Resolving the Error

Step 1: Verify SharePoint Folder URL

Ensure that the SharePoint URL used in the SharePoint.Contents function is correct. The URL should point to the folder containing the CSV files, and it should be properly formatted.

For example:

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SharePoint.Contents("https://company.sharepoint.com/sites/Solutions/DocumentStorage", [ApiVersion = 15])

Make sure that the URL is correct and points directly to the folder you intend to use. If the folder contains subfolders, you may need to modify the query to handle folder structures.

Step 2: Check the Data Type of the SharePoint Contents

After using the SharePoint.Contents function to access the SharePoint folder, the result will be a Table containing metadata about the files in the folder. Ensure that the table returned by SharePoint.Contents is being processed correctly.

Load the result of the SharePoint.Contents function into Power Query.

Inspect the data to ensure that it contains the expected file metadata, such as file names, file sizes, and file types.

Make sure that the file names and other metadata are being correctly interpreted as text, not as table values.

If you notice any issues with the data types, you may need to modify the query to explicitly convert columns to the correct data type.

Step 3: Correct Data Type Mismatches

If you identify that a table is being mistakenly used where text is expected, try using the Text.From() function to explicitly convert tables to text, or adjust the query logic to handle tables and text correctly.

For example, if you're extracting a column of file names and the data type is mismatched, you could use the following transformation:

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Table.TransformColumns(YourTable, {{"ColumnName", each Text.From(_)}})

This will ensure that the column is interpreted as text, avoiding the type mismatch.

Step 4: Check the CSV File Structure

If the issue is related to the structure of the CSV files in the SharePoint folder, review the CSV files to ensure they are correctly formatted. Inconsistent headers, missing values, or irregular column counts can cause issues during data loading and transformation.

You can use the CSV.Contents function in Power Query to preview the contents of a CSV file. Make sure the file is properly structured and that all columns are consistent.

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Csv.Document(File.Contents("path/to/your/file.csv"))

Step 5: Review Power Query Transformations

Review the steps in your Power Query editor to ensure that you are not applying any transformations that expect a text value but are receiving a table. For example, avoid using functions like Text.Select or Text.Contains on columns that are of type Table.

Step 6: Review SharePoint API Version

The SharePoint API version being used may impact the behavior of the SharePoint.Contents function. Ensure that you are using a compatible API version. If you're using an outdated version, try upgrading to the latest API version (e.g., ApiVersion = 16 or higher) to ensure better compatibility with the SharePoint folder and file types.

You can specify the API version in your query as follows:

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SharePoint.Contents("https://company.sharepoint.com/sites/Solutions/DocumentStorage", [ApiVersion = 16])

Step 7: Clear Cache and Retry

Sometimes, cached data in Power Query can cause issues during the refresh process. Clear the cache and attempt to refresh the dataflow again.

Frequently Asked Questions (FAQ)

1. What is the cause of the "We cannot convert a value of type Table to type Text" error?

The error typically occurs when a table is being used in a context where Power Query expects a text value. This can happen when trying to use text-specific functions (e.g., Text.Contains(), Text.Select()) on a table or when there's a data type mismatch during transformations.

2. How can I fix the "Mashup Exception" error in Power Query?

You can resolve the Mashup Exception error by carefully inspecting the data types being used in your transformations. Ensure that the correct data types (e.g., text, number, table) are being applied to the appropriate columns. Use functions like Text.From() to explicitly convert values when necessary.

3. Why does the SharePoint.Contents function fail to load data?

The failure could be due to incorrect URL, data type mismatches, irregular file structures in the SharePoint folder, or API version incompatibility. Ensure that the URL is correct, the file structures are valid, and that the transformations are applied correctly.

4. How do I retrieve CSV files from a SharePoint folder using Power Query?

Use the SharePoint.Contents function to access the folder, then filter the results to include only CSV files. After that, use the Csv.Document function to load the contents of each CSV file into Power Query.