Configure XML Formatting in Visual Studio Code: Step-by-Step

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Okay, here is a detailed article on configuring XML formatting in Visual Studio Code, aiming for approximately 5000 words.

Master XML Formatting in Visual Studio Code: A Comprehensive Step-by-Step Guide

Visual Studio Code (VS Code) has rapidly become one of the most popular code editors across various platforms and programming languages. Its lightweight nature, extensive customization options, and a vast ecosystem of extensions make it a powerful tool for developers. When working with data interchange formats like XML (Extensible Markup Language), maintaining consistent and readable code is crucial for collaboration, debugging, and overall project health. Poorly formatted XML can be a nightmare to parse visually, leading to errors and wasted time.

Fortunately, VS Code offers robust mechanisms for formatting code, including XML. While it has some basic built-in capabilities, the true power lies in leveraging extensions specifically designed for XML manipulation and formatting. This comprehensive guide will walk you through everything you need to know about configuring XML formatting in Visual Studio Code, from understanding the basics to mastering advanced techniques using popular extensions.

Why Does XML Formatting Matter?

Before diving into the “how,” let’s briefly touch upon the “why.” Consistent XML formatting offers several significant advantages:

  1. Readability: Properly indented elements, aligned attributes, and consistent line breaks make the hierarchical structure of XML immediately apparent. This drastically improves human readability, making it easier to understand the data structure and relationships.
  2. Maintainability: When XML files are consistently formatted, making changes, adding new elements, or modifying existing data becomes less error-prone. It’s easier to spot discrepancies or locate specific sections within a well-formatted document.
  3. Collaboration: In team environments, enforcing a standard formatting style ensures that everyone works with code that looks and feels the same. This reduces friction caused by differing personal preferences and makes code reviews more efficient, focusing on logic rather than style debates.
  4. Debugging: Locating syntax errors, mismatched tags, or incorrect attribute values is significantly easier in a cleanly formatted XML file. The visual structure helps isolate problems more quickly.
  5. Version Control: Consistent formatting minimizes noise in version control systems (like Git). Diff tools can more accurately highlight meaningful changes rather than showing large blocks of code modified simply due to whitespace or line break adjustments.
  6. Tool Integration: While XML parsers typically ignore whitespace between elements (unless xml:space="preserve" is used), some tools or processes might be sensitive to formatting, or their output might be easier to integrate if the input XML adheres to a standard format.

Prerequisites

To follow along with this guide, you’ll need:

  1. Visual Studio Code: Ensure you have a recent version installed. You can download it from the official VS Code website.
  2. Basic XML Knowledge: Familiarity with XML syntax (elements, attributes, nesting, comments, processing instructions) is assumed.

  3. A Sample XML File: Have a sample .xml file ready to experiment with formatting changes. You can create a simple one like this:

    xml
    <?xml version="1.0" encoding="UTF-8"?>
    <Bookstore>
    <Book category="FICTION">
    <Title lang="en">The Great Novel</Title><Author>Jane Doe</Author>
    <Year>2023</Year><Price>29.99</Price>
    </Book>
    <Book category="NON-FICTION"><Title lang="en">Learn XML Quickly</Title><Author>John Smith</Author><Year>2024</Year><Price>39.95</Price></Book>
    <!-- Add more books later -->
    <Magazine>
    <Title>Tech Weekly</Title>
    <Issue>Vol. 5, No. 12</Issue>
    </Magazine><EmptyElement />
    </Bookstore>

This intentionally messy example will be perfect for seeing the effects of formatting.

VS Code’s Built-in Formatting Capabilities (and Limitations)

VS Code includes a basic “Format Document” command. You can access it in several ways:

  • Keyboard Shortcut: The most common default shortcut is Shift+Alt+F (Windows/Linux) or Shift+Option+F (macOS).
  • Command Palette: Press Ctrl+Shift+P (Windows/Linux) or Cmd+Shift+P (macOS) to open the Command Palette, then type “Format Document” and select the command.
  • Right-Click Context Menu: Right-click anywhere within the XML document editor and select “Format Document.”

When you run this command without any specific XML formatting extensions installed, VS Code uses its built-in, language-agnostic formatter or relies on very basic language features. For XML, this often results in:

  • Basic indentation based on element nesting.
  • Possibly some line breaking.

However, the built-in formatter usually lacks the fine-grained control needed for professional XML formatting. It might not handle attributes elegantly, spacing within tags, self-closing tags consistently, or offer options for preserving whitespace in specific elements.

Example: Applying the default Format Document to our messy sample might result in something like this (results can vary slightly based on VS Code version and other configurations):

“`xml



The Great Novel
Jane Doe
2023
29.99


Learn XML Quickly
John Smith
2024
39.95



Tech Weekly
Vol. 5, No. 12



“`

This is an improvement, but it’s still quite basic. Notice how attributes remain on the same line as the element tag, and there’s no customization available for indentation size, tabs vs. spaces, or how empty elements are handled.

To achieve truly configurable and powerful XML formatting, we need to turn to extensions.

Leveraging Extensions for Powerful XML Formatting

The VS Code Marketplace is rich with extensions that enhance its capabilities. For XML formatting, two stand out:

  1. XML Tools (by Josh Johnson): This is arguably the most popular and feature-rich extension specifically focused on XML in VS Code. It provides extensive formatting options, XML validation (XSD/DTD), XPath evaluation, XQuery execution, and more. For formatting, it’s highly configurable.
  2. XML Language Support by Red Hat: Developed by Red Hat, this extension provides comprehensive XML language support based on the LemMinX XML language server. It includes formatting, validation, code completion (based on schemas), hover information, and diagnostics. While powerful, its formatting options might be slightly less numerous than those in XML Tools, but it integrates deeply with XML schemas.

Which Extension to Choose?

  • If your primary need is highly customizable formatting with many specific tweaks for indentation, attribute handling, spacing, etc., XML Tools is often the preferred choice.
  • If you need comprehensive XML language support, including robust schema-based validation, autocompletion, and diagnostics, alongside good formatting capabilities, the Red Hat XML extension is an excellent option.

It’s important to note that having both extensions installed and enabled simultaneously can lead to conflicts, especially regarding which one provides the formatting action. VS Code allows you to specify a default formatter for each language. If you install both, you’ll likely need to explicitly configure which one you want to use for XML formatting.

For this guide, we will primarily focus on configuring XML Tools by Josh Johnson due to its extensive and dedicated formatting options. We will also touch upon how to ensure it’s selected as the default formatter.

Step 1: Installing the XML Tools Extension

  1. Open VS Code.
  2. Navigate to the Extensions View by clicking the square icon on the Activity Bar (left-hand side) or by pressing Ctrl+Shift+X (Windows/Linux) or Cmd+Shift+X (macOS).
  3. In the search bar at the top, type XML Tools.
  4. Look for the extension named “XML Tools” by Josh Johnson. It usually has a high download count.
  5. Click the Install button for that extension.
  6. Once installed, you might be prompted to reload VS Code. It’s a good practice to do so (Developer: Reload Window from the Command Palette or simply restart VS Code).

Step 2: Setting XML Tools as the Default Formatter for XML

To avoid conflicts and ensure VS Code uses XML Tools when you request formatting for an XML file, you should explicitly set it as the default formatter for the XML language.

  1. Open an XML file (.xml) in VS Code.
  2. Open the Command Palette (Ctrl+Shift+P or Cmd+Shift+P).
  3. Type Format Document With... and select the command.
  4. You will be presented with a list of available formatters for XML. Choose “XML Tools” (it might be listed as DotJoshJohnson.xml).
  5. A prompt might appear asking if you want to set XML Tools as the default formatter for XML files. Choose “Yes” or “Configure Default Formatter…” and then select XML Tools.

Alternatively, you can configure this directly in your settings file:

  1. Open your Settings file. You can do this via:
    • UI: File > Preferences > Settings (or Ctrl+, / Cmd+,).
    • JSON: Open the Command Palette (Ctrl+Shift+P / Cmd+Shift+P), type Preferences: Open User Settings (JSON), and select it.

  2. Add or modify the following entry within the main JSON object:

    json
    "[xml]": {
    "editor.defaultFormatter": "DotJoshJohnson.xml"
    }

This explicitly tells VS Code to use the formatter identified by DotJoshJohnson.xml (which is XML Tools) whenever formatting is requested for files identified with the language mode xml.

Now, when you use Shift+Alt+F, the right-click menu, or the Format Document command in an XML file, VS Code will invoke the XML Tools formatter.

Step 3: Understanding and Configuring XML Tools Formatting Options

XML Tools offers a wide array of settings to tailor the formatting output precisely to your needs. You can configure these settings in two main ways:

  1. VS Code Settings UI:

    • Open Settings (Ctrl+, or Cmd+,).
    • In the search bar, type XML Tools Formatting. This will filter the settings to show only those related to XML Tools formatting.
    • You can then adjust the settings using dropdowns, checkboxes, and text input fields.

  2. settings.json File:

    • Open your User or Workspace settings.json file (as described previously).
    • Add or modify settings under the xmlTools.formatting key. This method offers more direct control and is useful for copying configurations or managing settings as code.

Let’s explore the key formatting settings provided by XML Tools:

Detailed Configuration Settings (xmlTools.formatting.*)

Below is a breakdown of the most important formatting settings available in XML Tools. We’ll use the JSON key names (e.g., xmlTools.formatting.indentation.style) as they appear in settings.json. You can find corresponding controls in the Settings UI.

1. Indentation (indentation)

  • xmlTools.formatting.indentation.style:

    • Description: Specifies whether to use tabs or spaces for indentation.
    • Values: "tab", "space"
    • Default: "space"
    • Example (settings.json):
      json
      "xmlTools.formatting.indentation.style": "tab"
    • UI: Look for “Indentation: Style” under XML Tools Formatting.

  • xmlTools.formatting.indentation.size:

    • Description: Sets the number of spaces or the width of a tab used for each indentation level. This is often influenced by editor.tabSize but can be overridden specifically for XML Tools here.
    • Values: An integer (e.g., 2, 4).
    • Default: Usually inherits from editor.tabSize (which defaults to 4).
    • Example (settings.json):
      json
      "xmlTools.formatting.indentation.size": 2
    • UI: Look for “Indentation: Size”.

  • xmlTools.formatting.indentation.preserveIntent:

    • Description: When enabled, the formatter tries to preserve the relative indentation of text content within elements, rather than forcing it to a specific level. This can be useful for mixed content or pre-formatted text blocks.
    • Values: true, false
    • Default: false
    • Example (settings.json):
      json
      "xmlTools.formatting.indentation.preserveIntent": true
    • UI: Look for “Indentation: Preserve Intent”.

2. Attributes (splitAttributes, splitXmlnsAttributes, attribute)

  • xmlTools.formatting.splitAttributes:

    • Description: Determines if attributes should be placed on new lines, indented under the element tag. This significantly impacts readability for elements with many attributes.
    • Values: true, false
    • Default: false
    • Example (settings.json):
      json
      "xmlTools.formatting.splitAttributes": true
    • UI: Look for “Split Attributes”.
    • Effect (true):
      xml
      <Book
      category="FICTION"
      id="bk101">
      <Title>...</Title>
      </Book>
    • Effect (false):
      xml
      <Book category="FICTION" id="bk101">
      <Title>...</Title>
      </Book>

  • xmlTools.formatting.splitXmlnsAttributes:

    • Description: Specifically controls whether XML namespace attributes (xmlns or xmlns:*) should be split onto new lines. Often used in conjunction with splitAttributes. You might want regular attributes split but keep xmlns declarations together on the first line, or vice-versa.
    • Values: true, false
    • Default: false (but behaviour might depend on splitAttributes if not explicitly set). It’s best to set this explicitly if you need specific xmlns handling.
    • Example (settings.json):
      json
      "xmlTools.formatting.splitAttributes": true, // Split regular attributes
      "xmlTools.formatting.splitXmlnsAttributes": false // Keep xmlns attributes on the first line
    • UI: Look for “Split Xmlns Attributes”.

  • xmlTools.formatting.newLine.attribute:

    • Description: Defines the character(s) to be inserted before each attribute when attributes are split onto new lines (splitAttributes is true). Typically used for indentation.
    • Values: A string, usually containing spaces or tabs matching your indentation settings.
    • Default: Usually calculated based on indentation.style and indentation.size (e.g., " " or "\t"). You generally don’t need to set this manually unless you want non-standard attribute indentation.
    • Example (settings.json):
      json
      // Manually set attribute indentation to 4 spaces, even if main indent is 2
      "xmlTools.formatting.newLine.attribute": " "
    • UI: Look for “New Line: Attribute”.

3. Spacing (space)

  • xmlTools.formatting.space.beforeAttributeEquals:

    • Description: Controls whether a space should exist before the = sign in attribute assignments (attribute = "value" vs attribute="value").
    • Values: true, false
    • Default: false
    • Example (settings.json):
      json
      "xmlTools.formatting.space.beforeAttributeEquals": true
    • UI: Look for “Space: Before Attribute Equals”.

  • xmlTools.formatting.space.afterAttributeEquals:

    • Description: Controls whether a space should exist after the = sign in attribute assignments (attribute= "value" vs attribute="value"). Note: This is less common stylistically.
    • Values: true, false
    • Default: false
    • Example (settings.json):
      json
      "xmlTools.formatting.space.afterAttributeEquals": true
    • UI: Look for “Space: After Attribute Equals”.

  • xmlTools.formatting.space.beforeClosingEmptyTag:

    • Description: Controls whether a space should precede the /> characters in a self-closing (empty) element tag (<EmptyElement /> vs <EmptyElement/>). Adding the space is common practice and often improves readability.
    • Values: true, false
    • Default: true
    • Example (settings.json):
      json
      "xmlTools.formatting.space.beforeClosingEmptyTag": false
    • UI: Look for “Space: Before Closing Empty Tag”.

4. Empty Elements (emptyElements)

  • xmlTools.formatting.emptyElements.selfClose:
    • Description: Determines how empty elements are represented. If true, uses the self-closing syntax (<tag/>). If false, uses an explicit start and end tag (<tag></tag>).
    • Values: true, false
    • Default: true
    • Example (settings.json):
      json
      "xmlTools.formatting.emptyElements.selfClose": false
    • UI: Look for “Empty Elements: Self Close”.
    • Effect (true): <EmptyElement />
    • Effect (false): <EmptyElement></EmptyElement>

5. Line Breaks and Whitespace Handling (newLine, preserveSpace, preserveAttributeSpace, maxLineLength)

  • xmlTools.formatting.newLine.element:

    • Description: Defines the character(s) inserted before a new element starts, effectively controlling indentation. Similar to newLine.attribute, this is usually derived from indentation settings. Manual override is rarely needed.
    • Values: A string (e.g., " ", "\t").
    • Default: Calculated based on indentation settings.
    • Example (settings.json):
      json
      // Highly unusual, but demonstrates overriding element indent string
      "xmlTools.formatting.newLine.element": "--"
    • UI: Look for “New Line: Element”.

  • xmlTools.formatting.newLine.header:

    • Description: Controls whether a newline should be placed after the XML declaration header (<?xml ... ?>).
    • Values: true, false
    • Default: true
    • Example (settings.json):
      json
      "xmlTools.formatting.newLine.header": false
    • UI: Look for “New Line: Header”.

  • xmlTools.formatting.newLine.text:

    • Description: If true, attempts to wrap long lines of text content within elements. This can be tricky and might not always produce ideal results depending on the content. Use with caution.
    • Values: true, false
    • Default: false
    • Example (settings.json):
      json
      "xmlTools.formatting.newLine.text": true
    • UI: Look for “New Line: Text”.

  • xmlTools.formatting.preserveSpace:

    • Description: An array of XML element tag names (case-sensitive) for which the formatter should not modify the internal whitespace (including line breaks and indentation). This is crucial for elements like <pre>, <script>, or any element where whitespace is significant. It mimics the behavior of the xml:space="preserve" attribute but applies during formatting based on tag name.
    • Values: An array of strings.
    • Default: [] (empty array)
    • Example (settings.json):
      json
      "xmlTools.formatting.preserveSpace": [
      "script",
      "style",
      "pre",
      "code",
      "CDATA" // Although CDATA is handled separately, sometimes useful here
      ]
    • UI: Look for “Preserve Space”. You can add multiple tag names here.

  • xmlTools.formatting.preserveAttributeSpace:

    • Description: If true, the formatter attempts to preserve whitespace within attribute values. If false, it might normalize whitespace (e.g., collapse multiple spaces into one).
    • Values: true, false
    • Default: false (Note: Be cautious, as preserving exact whitespace in attributes is less common and might hide issues). Consider if true is really needed.
    • Example (settings.json):
      json
      "xmlTools.formatting.preserveAttributeSpace": true
    • UI: Look for “Preserve Attribute Space”.

  • xmlTools.formatting.maxLineLength:

    • Description: Specifies a preferred maximum line length. The formatter will attempt to break lines (e.g., by splitting attributes or potentially text if newLine.text is true) to stay within this limit. This is not a hard guarantee, especially for long, unbreakable strings or deeply nested structures. Set to 0 to disable line length constraints.
    • Values: An integer (e.g., 80, 120, 0).
    • Default: 0 (disabled)
    • Example (settings.json):
      json
      "xmlTools.formatting.maxLineLength": 100
    • UI: Look for “Max Line Length”.

6. Comments and Processing Instructions (removeComments, removeProcessingInstructions)

  • xmlTools.formatting.removeComments:

    • Description: If true, the formatter will remove all XML comments (<!-- ... -->) during the formatting process. Use with extreme caution! This is a destructive action and typically not desired unless you specifically need to strip comments for a particular output.
    • Values: true, false
    • Default: false
    • Example (settings.json):
      json
      // Warning: This will delete comments!
      "xmlTools.formatting.removeComments": true
    • UI: Look for “Remove Comments”.

  • xmlTools.formatting.removeProcessingInstructions:

    • Description: If true, the formatter removes all Processing Instructions (<?target ... ?>), excluding the main XML declaration (<?xml ... ?>). Similar to removeComments, this is destructive and should be used carefully.
    • Values: true, false
    • Default: false
    • Example (settings.json):
      json
      // Warning: This will delete processing instructions!
      "xmlTools.formatting.removeProcessingInstructions": true
    • UI: Look for “Remove Processing Instructions”.

7. Miscellaneous

  • xmlTools.formatting.enforcePrettySelfClosingTagOnFormat:
    • Description: This seems related to ensuring self-closing tags have consistent spacing before the />, potentially overlapping with space.beforeClosingEmptyTag. Check the extension’s documentation for the most current behavior. It likely reinforces the standard <tag /> format.
    • Values: true, false
    • Default: true (usually)
    • Example (settings.json):
      json
      "xmlTools.formatting.enforcePrettySelfClosingTagOnFormat": true
    • UI: May be implicitly controlled by other settings or appear as “Enforce Pretty Self Closing Tag”.

Step 4: Applying Your Configuration – User vs. Workspace Settings

VS Code allows you to configure settings at different levels, which provides flexibility for personal preferences versus project-specific standards:

  • User Settings (settings.json in User directory):

    • Scope: Apply globally to all projects you open in VS Code.
    • Location: Varies by OS. Access via Command Palette: Preferences: Open User Settings (JSON).
    • Use Case: Define your personal default formatting preferences that you like to use across different projects.

  • Workspace Settings (.vscode/settings.json in your project folder):

    • Scope: Apply only to the specific project (folder) where the .vscode directory resides. These settings override User settings.
    • Location: Create a .vscode folder in your project’s root directory, and inside it, create a settings.json file.
    • Use Case: Define project-specific formatting rules that everyone working on the project should adhere to. This file can (and often should) be committed to version control (e.g., Git) to ensure consistency across the team.

Example Workspace /.vscode/settings.json for Team Consistency:

“`json
{
// General editor settings for the project
“editor.tabSize”: 2,
“editor.insertSpaces”: true,
“files.eol”: “\n”, // Enforce Unix-style line endings

// XML specific settings using XML Tools
“[xml]”: {
“editor.defaultFormatter”: “DotJoshJohnson.xml”,
“editor.formatOnSave”: true, // Automatically format XML files on save
“editor.tabSize”: 2, // Ensure XML uses 2 spaces if different from global
“editor.insertSpaces”: true
},

// XML Tools formatting configuration for this project
“xmlTools.formatting.indentation.style”: “space”,
“xmlTools.formatting.indentation.size”: 2,
“xmlTools.formatting.splitAttributes”: true, // Attributes on new lines
“xmlTools.formatting.splitXmlnsAttributes”: true, // Namespace attributes also on new lines
“xmlTools.formatting.space.beforeClosingEmptyTag”: true, // Use
“xmlTools.formatting.emptyElements.selfClose”: true, // Use self-closing tags
“xmlTools.formatting.preserveSpace”: [ “script”, “style”, “description” ], // Preserve space in these tags
“xmlTools.formatting.maxLineLength”: 120, // Try to keep lines under 120 chars
“xmlTools.formatting.removeComments”: false, // Keep comments
“xmlTools.formatting.removeProcessingInstructions”: false // Keep PIs
}
“`

By using Workspace settings, you ensure that any developer opening this project in VS Code (with the XML Tools extension installed) will automatically use these formatting rules, promoting consistency.

Step 5: Triggering Formatting

Once you have installed the extension, set it as default, and configured the options, you can format your XML documents using the standard VS Code methods:

  1. Manual Formatting:

    • Open the XML file.
    • Use the keyboard shortcut (Shift+Alt+F or Shift+Option+F).
    • Or, open the Command Palette (Ctrl+Shift+P / Cmd+Shift+P), type Format Document, and press Enter.
    • Or, right-click in the editor and select Format Document.

  2. Formatting a Selection:

    • Select a specific portion of your XML code.
    • Use the keyboard shortcut (Ctrl+K Ctrl+F on Windows/Linux, Cmd+K Cmd+F on macOS) – Note: This shortcut might vary.
    • Or, open the Command Palette and type Format Selection.
    • Or, right-click the selection and choose Format Selection.
    • XML Tools will format only the selected fragment.

  3. Formatting on Save (Highly Recommended for Consistency):

    • This is often the most convenient way to ensure your files are always formatted correctly.
    • Open your User or Workspace settings.json.

    • Add or modify the following settings:

      “`json
      {
      // Option 1: Enable format on save for ALL files (use with caution)
      // “editor.formatOnSave”: true,

      // Option 2: Enable format on save ONLY for XML files (Recommended)
"[xml]": {
    "editor.formatOnSave": true,
    // Ensure the default formatter is also set here or globally
    "editor.defaultFormatter": "DotJoshJohnson.xml"
},

// Other settings...

      }
      “`

    • With "editor.formatOnSave": true enabled for [xml], every time you save an XML file (Ctrl+S / Cmd+S), VS Code will automatically run the XML Tools formatter using your configured settings.

Step 6: Experimenting and Refining

The best way to master XML formatting is to experiment. Take your sample XML file (or a real-world one) and try different combinations of settings:

  • See the difference between splitAttributes: true and false.
  • Try tab vs space indentation with different sizes (2 vs 4).
  • Observe how emptyElements.selfClose: false changes <EmptyElement />.
  • Add a tag like <Description> with indented text inside, then add "Description" to xmlTools.formatting.preserveSpace and see how formatting changes.
  • Set a low maxLineLength (e.g., 40) and see how the formatter attempts to wrap attributes.

Use the Settings UI for quick adjustments or edit settings.json directly for more complex configurations. Remember that Workspace settings override User settings, allowing project-specific rules.

Putting It All Together: A Formatting Example

Let’s apply a specific configuration to our initial messy XML:

Desired Configuration (settings.json):

json
{
"[xml]": {
"editor.defaultFormatter": "DotJoshJohnson.xml",
"editor.formatOnSave": false // Manual formatting for this example
},
"xmlTools.formatting.indentation.style": "space",
"xmlTools.formatting.indentation.size": 2,
"xmlTools.formatting.splitAttributes": true,
"xmlTools.formatting.splitXmlnsAttributes": true, // Though none in sample
"xmlTools.formatting.space.beforeClosingEmptyTag": true,
"xmlTools.formatting.emptyElements.selfClose": true,
"xmlTools.formatting.preserveSpace": [], // No preserved space needed here
"xmlTools.formatting.maxLineLength": 0 // No line limit
}

Original Messy XML:

“`xml



The Great NovelJane Doe
202329.99

Learn XML QuicklyJohn Smith202439.95


Tech Weekly
Vol. 5, No. 12


“`

After Applying Format Document (Shift+Alt+F) with the above configuration:

“`xml



The Great Novel
Jane Doe
2023
29.99


Learn XML Quickly
John Smith
2024
39.95


Tech Weekly
Vol. 5, No. 12



“`

Notice the changes:
* Indentation is now 2 spaces.
* Attributes (category, lang) are split onto new lines, indented relative to their element.
* Elements like <Author>, <Year>, <Price> that were previously on the same line are now properly indented on separate lines.
* The comment is preserved and correctly indented.
* The empty element uses the self-closing format with a space before />.

This demonstrates the power and flexibility offered by configuring the XML Tools extension.

Troubleshooting Common Formatting Issues

Sometimes formatting might not work as expected. Here are common problems and solutions:

  1. Formatting Not Working at All:

    • Check Extension: Ensure XML Tools (or your chosen formatter) is installed and enabled in the Extensions view (Ctrl+Shift+X). Disabled extensions won’t work.
    • Check Default Formatter: Verify that the correct formatter is set as default for XML files ("[xml]": { "editor.defaultFormatter": "DotJoshJohnson.xml" }). Use Format Document With... to check and select if needed.
    • Valid XML: The formatter might fail if the XML document contains significant syntax errors. Try validating the XML first (XML Tools also has validation features, or use an online validator). Fix errors and try formatting again.
    • VS Code Restart: Sometimes, a simple reload or restart of VS Code (Developer: Reload Window or close/reopen) can resolve temporary glitches.

  2. Incorrect Formatting Results:

    • Review Settings: Double-check your xmlTools.formatting.* settings in both User and Workspace settings.json. Remember Workspace settings override User settings. Ensure the settings match your desired output (e.g., splitAttributes, indentation.size).
    • Conflicting Settings: Look for other general editor settings (like editor.tabSize, editor.insertSpaces) that might conflict or interact unexpectedly. Ensure the [xml] specific overrides are correctly set if needed.
    • preserveSpace: Check if the element you’re having trouble with is listed in the xmlTools.formatting.preserveSpace array. If so, the formatter is intentionally leaving its content alone.
    • Extension Bug: While rare for mature extensions, a bug could be the cause. Check the extension’s GitHub repository issues page to see if others have reported similar problems or if an update is available.

  3. Formatting on Save Not Working:

    • Check Setting: Ensure "editor.formatOnSave": true is correctly set within the "[xml]": {} block in your settings.json.
    • Default Formatter: Format on Save requires a default formatter to be configured for the language. Ensure editor.defaultFormatter is set for XML.
    • File Not Recognized as XML: Make sure VS Code correctly identifies your file’s language mode as “XML” (visible in the bottom-right status bar). If not, you might need to associate the file extension with the XML language (files.associations setting).

  4. Performance Issues on Large Files:

    • Formatting very large XML files (hundreds of MB or more) can sometimes be slow or consume significant memory.
    • Disable Format on Save: For extremely large files, you might want to disable formatOnSave and only format manually when needed.
    • Format Selection: Format smaller chunks of the file using Format Selection.
    • Check Extension Updates: Performance improvements are often included in extension updates.

  5. Settings in .vscode/settings.json Not Applying:

    • Syntax Errors: Ensure the settings.json file itself is valid JSON. VS Code will often highlight syntax errors.
    • Correct Location: Verify the file is exactly at .vscode/settings.json relative to your project root.
    • Workspace Open: Make sure you have opened the folder containing the .vscode directory as your workspace root in VS Code (File > Open Folder…). Settings only apply to the currently open workspace.

Advanced Considerations

  • .editorconfig: If your project uses an .editorconfig file for cross-editor coding style consistency, VS Code (via extensions like EditorConfig for VS Code) may respect some of its settings (like indent_style, indent_size). These can potentially interact with or override VS Code’s own settings or the XML Tools settings. Be aware of the precedence: EditorConfig often takes high priority for the settings it covers. However, .editorconfig typically doesn’t support the fine-grained XML-specific options like splitAttributes. You’ll still need settings.json for those.
  • Integrating with Linters/Validators: While this guide focuses on formatting (style), you often use it alongside validation (correctness against a schema like XSD or DTD) and potentially linting (checking for best practices or potential issues not covered by schema validation). Both XML Tools and the Red Hat XML extension provide validation capabilities. Ensure your formatting doesn’t conflict with validation requirements (though usually, formatting improves clarity for validation).
  • Conditional Formatting: VS Code settings don’t easily support conditional logic (e.g., “split attributes only if there are more than 3”). You set one rule via the configuration, and the formatter applies it consistently.
  • Custom Formatting Scripts: For highly specialized or complex formatting rules beyond what extensions offer, the ultimate solution could involve writing a custom script (e.g., using Python with xml.dom.minidom or lxml, or an XSLT transformation) and potentially invoking it via a VS Code Task. This is significantly more complex and outside the scope of standard configuration.

Conclusion

Consistent, readable XML is not just an aesthetic preference; it’s a cornerstone of efficient development, collaboration, and maintenance when working with this ubiquitous data format. Visual Studio Code, enhanced by powerful extensions like XML Tools, provides a comprehensive and highly configurable environment for achieving precisely the XML formatting style you need.

By following the steps outlined in this guide—installing an extension, setting it as the default formatter, meticulously configuring options like indentation, attribute splitting, spacing, and empty element handling via the Settings UI or settings.json, and leveraging features like Format on Save—you can transform potentially chaotic XML into clean, structured, and easily understandable documents.

Remember to differentiate between User settings for personal preferences and Workspace settings (.vscode/settings.json) for project-wide standards, ensuring team consistency. Don’t hesitate to experiment with the various configuration options provided by XML Tools to find the perfect setup for your workflow and project requirements. Taking the time to configure XML formatting properly in VS Code is an investment that pays dividends in clarity, reduced errors, and improved productivity. Happy formatting!

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