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Improve your Craft CMS skills

Troubleshooting Guide: An Error Occurred When Rendering A Template In Craft CMS

10 min read
Shape April 2022 HR 202

Template errors in Craft CMS can bring sites crashing down, yet debugging vague error messages often proves frustrating. This guide arms developers with actionable troubleshooting techniques to efficiently diagnose those obscure 'template not found' and 'unexpected tag' gremlins. Learn systematic workflows to resolve errors and delve into practical debugging tools. Soon, you'll tackle tedious template issues with confidence.

When debugging template errors in Craft CMS, systematically check full error messages, validate file paths and variables set, eliminate caching issues, fix diagnosed syntax and context problems. Learning debugging skills and documenting issues prevents future errors.

Troubleshooting Template Errors in Craft CMS

Overview of Templating in Craft CMS

Craft CMS utilizes the versatile Twig templating engine to render templates on the front-end of sites. Twig syntax enables the use of variables, filters, tags, and other functionality to build dynamic templates. Common Twig features used in Craft include:

  • Variables to output content from fields, categories, assets, etc.

  • Filters to modify variables

  • Tags like {% if %} and {% for %} for logic and looping

  • Macros to reuse code

  • Blocks to extend layouts

With the power of Twig comes complexity. Template errors like incorrect syntax, wrong paths, infinite loops, etc. are common. Caching can also lead to misleading issues if outdated templates are served. Carefully debugging errors is crucial.

Importance of Troubleshooting Template Issues

Thoroughly troubleshooting template errors in Craft is critical for a smooth site experience. Unlike a static HTML site, a minor typo in a Craft template can break an entire page or site section. Front-end issues also directly impact end users.

For example, an incorrect variable could cause a blank page, destroying conversion rates. An infinite loop may crash the server. Layout problems will frustrate users. Without debugging, locating the source of these errors is difficult.

Methodically testing templates locally and reviewing Craft logs can identify bugs. For syntax issues, the Twig documentation is invaluable. Stack Overflow often has fixes for common errors. When bugs arise on live sites, it's essential to calmly debug instead of making rushed changes.

Patience and systematically ruling out causes using Craft and Twig resources will uncover most template gremlins. Leaving issues unresolved affects site stability and user experience, so persistently yet carefully debugging is key. With complex sites, bugs are inevitable but identifying root causes through troubleshooting will lead to robust templates.

Identifying and Analyzing Template Error Messages

Examining the Full Error Message

When a template error occurs in Craft CMS, the first step is examining the full error message. Instead of just the brief frontend output, check template-related error logs and stacks for the complete message text.

The specific wording provides vital clues for troubleshooting. For example, a "syntax error" indicates a problem with Twig formatting or variables. A "file not found" error points to an incorrect path or missing template. Errors about infinite loops or max executions suggest an endless loop.

Carefully reading the error text identifies the actual issue. Phrases like "unknown variable" or "unexpected '" characterize the error for debugging. Code excerpts also help pinpoint problem spots in templates. Decode and research the specifics from the message rather than relying on the error title only.

Searching Support Forums and Documentation

With the full error text, search Craft CMS support forums, Stack Overflow, and Twig documentation for potential solutions. Generic searches like "Craft template error" are less effective than the specific message. For common errors, existing fixes will appear.

For example, searching for "Twig syntax error unexpected ''" provides tweaks to try in that situation. If the error text is unique, look for related issues that could share causes. Approach new errors methodically, as existing answers may already solve it. Leverage the solutions others have shared.

Troubleshooting Related Error Messages

Look for error messages involving similar issues that could share causes. A missing asset and missing template error may stem from the same incorrect path. Different syntax errors could originate from one formatting problem. Identify the commonalities between errors.

Even for unique error messages, search on partial text. A "class not found" error may match a "method not found" issue. Isolate and research the generic phrases within the message, as fixes for related terms can provide clues. Template issues often group into similar categories and tracing those helps uncover solutions.

Methodically analyzing error messages provides a framework for troubleshooting. Rather than getting frustrated, embrace error text as an aid for iterative debugging. Support forums, documentation, and past experience will help decipher and resolve Craft CMS template errors over time.

Verifying Template Paths, Files and Settings

Checking Template Paths and Filenames

Many template errors relate to incorrect paths or filenames. Always verify these reference the right location. Check for typos like misspelled folder names or missing extensions. Confirm files exist on the disk at those paths.

Use Twig's dump() and source() functions to output real paths used. Try temporary test templates to isolate issues. Path problems can originate from front-end links, different environments, or moved files.

When including other templates, validate the relative paths. Use aliases in config/general.php for reusable paths. For assets and other variables, test exact paths passed. Eliminate doubt about referenced locations by thoroughly checking paths and filenames.

Reviewing Template Settings and Configuration

Look over template settings that could cause conflicts. Ensure caching is disabled locally and stale templates aren't being served. Review inheritance chains and possible overrides like base templates.

Check template folder configurations like isFrontend flags. Confirm Craft recognizes files as templates and prefixes like _ aren't blocking them. Overlooked settings around versions, caching, or locations can lead to misleading errors.

Confirming Template Version and File Permissions

Verify the template file contents match the current version control commit if using Git. Local changes or outdated pulls can make errors seem unexplained. Ensure proper permissions are set on template files so Craft can access them.

Check that files exist on disk as expected at the specified paths and aren't missing.

Environments may differ in what's deployed. Double-check folder case sensitivity. Confirming core assumptions around file existence, versions, and access resolves obscure errors.

Carefully inspecting paths, settings, files, and configurations eliminates many misleading issues. Template errors often stem from incorrect references or unexpected environments. Tracing the references down to their real locations takes time but avoids endless debugging cycles.

Debugging Template Context and Variables

Verifying Context Variables Are Set

Many template errors originate from missing or incorrect context variables. Verify controllers and services properly set all variables required in templates.

Pass temporary test variables from controllers to isolate issues. Check variable types match expectations, like ensuring an array rather than string is passed. Test with hard-coded values to pinpoint problems.

Examine the template logic to confirm the required context variables are actually used. It's possible unused legacy variables remain set incorrectly. Understanding exactly what templates need streamlines debugging efforts.

Enabling Dev Mode for Variable Inspection

Enable Craft's devMode configuration to inspect all variables made available to templates during execution. This helps identify variables that are missing or unexpected.

With devMode, use Twig's dump() function liberally in templates to output variables. Look for undefined variables or incorrect values being set in the context. DevMode exposes ambiguity around what templates actually receive.

Logging Variable State During Execution

Complement devMode by logging context variables at key points in templates before issues occur. Track state flows to catch variable changes leading to errors.

Log when variables are set in controllers and again right before use in templates. Differences in values indicate where problems arise.

Logging also clarifies complex template execution flows across multiple includes, macros, and blocks. Tracing variable flows using logging shines light on obscure logic bugs.

Carefully confirming expected variables are set and logging values during execution helps uncover template issues that may not directly manifest as errors. A missing variable can lead to blank pages rather than crashes. Meticulous debugging principles pay dividends for complex template troubleshooting.

Checking Caching, Assets and Environments

Clearing Caches and Rebuilding Assets

A common troubleshooting step is clearing all Craft CMS caches and rebuilding front-end assets. Stale cached templates can cause confusing errors unrelated to code changes.

Clear the data, template, and asset caches in the Craft admin. Then rebuild assets to invalidate any outdated front-end caches. Test after clearing to see if errors persist.

Caching provides performance but obscures problems. Eliminate it as a factor when debugging errors. Force freshly parsed templates by rebuilding caches.

Comparing Working and Failing Setups

For intermittent errors, compare environments between working and failing setups. Differences in PHP versions, web servers, OS, plugins etc. can cause issues.

Recreate the same combination of software if possible. Check server logs for variances as well. Note any patterns around when issues manifest. Isolate the key change leading to failures.

Testing on a Clean Install

As a robust test, install a clean instance of Craft CMS with no plugins or custom code. Replicate only the template causing issues. This completely isolates the problem.

Test on a fresh environment to narrow down any conflicts from plugins, modules, or project code. Strip away complexity and server differences.

Starting clean validates if the issue stems from core Craft, the template, or other factors like caching and environments. Pinpoint the root cause by incrementally adding complexity back.

Eliminating red herrings around caching, assets, environments, and project code allows focusing on the template logic itself. Methodically isolate and validate assumptions to expose the true error source.

Fixing Identified Template Issues

Correcting Template Syntax Errors

Once identified, fix any Twig syntax, formatting, parsing, or logic errors causing template issues. Common problems include incorrect {% set %} naming, missing {% endif %}, extra commas, and invalid operators.

Consult Twig documentation and error messages for tweak guidance. Formatting mistakes can often be corrected quickly once pinpointed. Use an IDE with Twig support to avoid typos.

Fixing syntax and formatting issues improves error resilience and future template editing. Formatting consistency and correctness eliminates frustrating low-level bugs.

Adjusting Template Context Variables

With incorrect context variables diagnosed, adjust templates to expect the actual data provided.

Fix variable names, enable missing values required, massage formats, or default nulls.

Isolate variables into reusable macros to contain impact. Rename any unintuitive variable names sending the wrong data. Normalize data formats like enforcing arrays.

Adapt templates to real world variables rather than expecting ideal data. Defensive coding prevents variable-related bugs emerging later.

Addressing Caching and Asset Issues

For caching and asset issues found, adjust invaliation and versioning schemes. Configure Craft and web server caching correctly for dev/prod environments.

Tune CP asset generation settings and front-end cache headers for optimal debugging and performance. Fix misconfigured, outdated or missing asset and cache settings affecting templates.

Resolve identified caching and asset problems through configuration tuning anddbg courseoutline debugging. Don't let ambient caching obscure fixes and cause confusion.

Adjusting templates to address diagnosed issues such as context, caching, assets, and syntax errors is critical after troubleshooting reveals the specific problems. Fix the identified root causes rather than just the symptoms.

Preventing Future Template Errors

Improving Debugging Skills

Improving debugging skills helps prevent and quickly fix future template errors. Enable DevMode by default during all development for full variable inspection.

Logically place template logging statements to trace execution flows. Master Craft breakpoints and VarDumper for live debugging. Know Twig’s dump, source, and debugging functions.

Solid debugging fundamentals dramatically accelerate troubleshooting. For complex projects, use profilers to identify performance bottlenecks. Learn debugging workflows rather than relying on haphazard efforts.

Implementing Stricter Code Reviews

Enforce diligent code reviews and testing for all new templates before deploying live. Peer review identifies logic gaps, architecture improvements, and potential bugs.

Rigorously review all template code, not just business logic. Template errors often stem from assumptions, typos, and edge cases. Reviews shine light on overlooked issues.

The review process improves code quality and provides knowledge sharing on templates. Taking the time prevents many subtle bugs reaching production.

Learning from Past Template Issues

Keep documentation on previously fixed template errors and their diagnoses. Create a knowledge base of lessons learned during troubleshooting.

Catalog common pitfalls like local vs production path differences. Note obscure caching problems encountered. Internal documentation distills hard-won experience into actionable improvements.

With detailed historical references, similar issues can be rapidly decoded rather than repeating past debugging. Apply the same meticulous methodology against new template problems.

Combining improved skills, reviews, and documentation processes leverages experience into creating resilient templates. A diligent methodology prevents regressing into intractable errors.

Shape April 2022 HR 202
Andy Golpys
- Author

Andy has scaled multiple businesses and is a big believer in Craft CMS as a tool that benefits both Designer, Developer and Client. 

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