Error Handling with Expressions in Power Automate

⚠️ Error Handling with Expressions in Power Automate

Error handling with expressions in Power Automate is crucial for building resilient flows that can gracefully respond to issues like missing data, failed actions, or null values. Expressions let you anticipate, catch, and respond to runtime errors — without interrupting the entire flow.

With the right combination of functions and logic, you can catch potential errors, return fallback values, or route the flow differently to avoid failure.

📚 Why Error Handling Matters in Power Automate

Power Automate flows may break due to:

Missing or invalid data
Null or undefined values
API failures or timeouts
Division by zero or string parsing issues
Skipped or failed actions

Using error handling with expressions in Power Automate, you can:

Prevent flows from terminating unexpectedly
Display user-friendly error messages
Route errors to alternate logic branches
Log issues to SharePoint, email, or Dataverse

🧰 Error Handling Expression Functions Reference

Function	Description	Example	Result
`coalesce(a, b)`	Returns the first non-null value	`coalesce(null, 'Default')`	`'Default'`
`if(condition, true, false)`	Conditional check	`if(equals(1,1),'OK','Fail')`	`'OK'`
`equals(a, b)`	Checks for equality	`equals(5,5)`	`true`
`empty(value)`	Checks if value is empty	`empty(triggerBody()?['Email'])`	`true/false`
`contains(text, value)`	Checks if string contains value	`contains('abc', 'a')`	`true`
`hasProperty(object, key)`	Checks if a property exists	`hasProperty(triggerBody(), 'email')`	`true/false`
`tryCatch()` (via scopes)	Manual try-catch logic	–	Error-safe branching
`isNull(value)`	Returns true if value is null	`isNull(null)`	`true`
`int()`, `float()`, etc.	Safe type conversion	`int('abc')`	Error-prone unless checked

💼 Real-World Use Cases

Scenario	Expression	Purpose
Handle missing user email	`coalesce(triggerBody()?['Email'], 'default@email.com')`	Prevent null failure
Log failed step status	`outputs('Get_Item')?['statusCode']`	Detect 400/500 errors
Route based on success/failure	`if(equals(outputs('HTTP')?['statusCode'], 200), 'Success', 'Fail')`	Control flow
Check if a value exists	`hasProperty(triggerBody(), 'email')`	Prevent runtime errors
Use fallback value	`if(empty(triggerBody()?['Comments']), 'No comments', triggerBody()?['Comments'])`	Better UX

🧪 Examples of Error Handling with Expressions in Power Automate

1. Fallback Email Address with `coalesce()`

coalesce(triggerBody()?['Email'], 'default@email.com')

Use Case: Prevents null reference if Email isn’t provided.

2. Detecting Empty Fields

if(empty(triggerBody()?['Notes']), 'No notes available', triggerBody()?['Notes'])

Use Case: Prevents empty display values in approval emails.

3. Handling Action Failures Gracefully

if(equals(outputs('HTTP')?['statusCode'], 200), 'Success', 'API Failed')

Use Case: Log or respond differently based on API result.

4. Check for Missing Properties

if(hasProperty(triggerBody(), 'Manager'), triggerBody()?['Manager'], 'N/A')

Use Case: Prevents flow from breaking when a field is missing.

5. Avoid Division by Zero

if(equals(variables('Denominator'), 0), 'Undefined', div(variables('Numerator'), variables('Denominator')))

Use Case: Prevents runtime error when dividing numbers.

✅ Best Practices for Error Handling with Expressions

✅ Use coalesce() to provide safe default values
✅ Always check for null or empty() values before using them
✅ Use hasProperty() before referencing dynamic properties
✅ Wrap risky logic (like division or conversion) in if() statements
✅ Combine with Configure Run After to control action failures
✅ Use Scopes to build try/catch logic with Success/Failure/Timeout branches

⚠️ Common Pitfalls and How to Avoid Them

Pitfall	Cause	Fix
Flow fails on null value	Directly accessing undefined fields	Use `coalesce()` or `hasProperty()`
Unexpected output in emails	Empty strings or nulls in content	Use fallback logic with `if()`
Breaking on failed actions	Not using `Configure Run After`	Use failure paths in scopes
Expression not evaluating	Wrong property path	Use Peek Code to verify structure
Error on conversion	Invalid string in `int()` or `float()`	Wrap with `if()` or validate first

📘 Summary: Mastering Error Handling with Expressions in Power Automate

Use error handling with expressions in Power Automate to:

Create fail-proof flows that don’t crash on invalid or missing data
Provide clear, helpful messages or fallback outputs
Log and trace failures to improve visibility
Adapt flow behavior dynamically using metadata and condition checks

Curriculum

Error Handling with Expressions in Power Automate