ErrorRecord.Grammar.md

• Inline throw
• Function: Error.Record() signature
• See Also
• Examples from the Docs
• Extra Requirements Specific to Try Catch
• Try Expression Types
  • Try catch (e) =>
  • Try catch () =>
  • Try otherwise
  • Try
• yaml summary

Inline throw

error is the name of a language keyword that throws an exception. There's a built in function named Error.Record to construct the argument record for you

error [
  Reason = "Business Rule Violated", 
  Message = "Item codes must start with a letter", 
  Detail = "Non-conforming Item Code: 456"
]

To get a GUID to easily filter query tracing, you can Table.AddColumn() a guid for traces using trace specific rows to specific Diagnostics.ActivityId() as text

= Diagnostics.ActivityId()

Function: Error.Record() signature

Creates the record to throw

Error.Record(
    reason as text,
    optional message as nullable text,
    optional detail as any,
    optional parameters as nullable list) as record

See Also

• what's new: New Power Query M Language Keyword: catch
• pq docs Error.Record()
• Diagnostics.Trace()
• Diagnostics.ActivityId() as text
• what's new: bengribaudo.com: Structured Error Messages
• bengribaudo.com: power-query-m-primer-part-15-error-handling
• Power Query Formal Language Specs.pdf

Examples from the Docs

The Ellipsis expression is sugar for throwing this expression

x =...

is equivalent to

x = error Error.Record("Expression.Error", "Not Implemented")

This expression

x = error Error.Record(
    "FileNotFound", "File my.txt not found", "my.txt")

is equivalent to

x = error [
    Reason = "FileNotFound",
    Message = "File my.txt not found",
    Detail  = "my.txt"
]

more examples

Extra Requirements Specific to Try Catch

• The catch function must be defined inline, so a reference to a function cannot be used.
• each cannot be used to define the catch-function
• the function defintion cannot include any type constraints

Try Expression Types

Try catch (e) =>

= Table.AddColumn(
Source, 
    "Clean Standard Rate",
    each 
        try [Standard Rate]
        catch (e) =>
            if e[Message] = "Invalid cell value '#REF!'." then [Special Rate] * 2
            else if e[Message] = "Invalid cell value '#DIV/0!'." then [Special Rate] / 3
            else 0
)

Try catch () =>

Functionally equivalent to try <e> otherwise <e>

let
    x = try 1 / 0
        catch () => "null"
in 
    x

Try otherwise

let
    x = try 1 / 0 
        otherwise "null"
in 
    x

Try

let
    x = try "A"
in
    if x[HasError] then x[Error] else x[Value]

yaml summary

returns:
    type: record
reason: 
    type: text
    default: "Expression.Error"
    notes: . | 
        the default value isn't mandatory, may be implementation details and change
message:
    type: optional nullable text

detail:
    type: optional detail as any

parameters:
    type: optional nullable list