What Not To Do: When Letting Your Code Breathe Goes Bad

White Space before a function call is allowed

Whitespace between function calls and the name are allowed. Including newlines
These are equivalent statements:

= DoStuff( args )

// and
= DoStuff

                                ( 
args )

Record lookups also allow whitespace.
This is totally valid syntax wise. Not necessarily morally though.

let
    Func = () => [ 
        user = [ Name = "bob" ] 
    ]
in 
    Func  


(

              )
                            
                                             [    
     user  



]

Misleading Comments inside Lists, Records, and Function Calls are allowed

Comments do not affect parsing or execution.
Without syntax highlighting it looks like 4 is the final item in the list

let
    num = List.Count( { 0
                     ..
       5 } & { 3, 4                                                  /*
    }) /* fake ending here  here * /
                
    without syntax highlighting, it looks like the func call ended
    
    later, secretly do more
*/                                                  ,99 } )

in num

Now it’s slightly easier

let
    num = List.Count( { 0
                     ..
       5 } & { 3, 4                                                  /*
    }) /* fake ending here  here * /
                
    without syntax highlighting, it looks like the func call ended
    
    later, secretly do more
*/                                                  ,99 } )

in num

The list operator .. allows a lot of expressions

• See: powerquery-m/m-spec-consolidated-grammar#list-expression

You can use inline comments, resuming the list expression later

let
    num = List.Count( { 0
..
           5 } & { 3, 4 /*
    now do more */ } )
in num

You don’t have to wrap the try-catch expressions in parenthesis.

let l = { 
          try "foo" + 99 catch (e) => 3           ..
          try File.Contents( "invalid" ) catch () => 7 } 
in 
    l = { 3..7 } // is true

This version gave an interesting error. I thought perhaps try-catch expressions doesn’t work for inline list indices ?

let g = { 
          try 10 catch (e) => 3           ..
          try 27 / 0 catch () => 53 }

in g

Expression.Error: The number is out of range of a 32 bit integer value.
Details:
    Infinity

But then realized division by 0 in power query does not throw an error record. It has the type number.