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Experiment Getting-Started Power BI Uncategorized

Inspecting Function “subtypes” in Power Query

PowerQuery has metadata that you don’t normally see. For example, take the function Table.FromRecords

Create a new blank query, and set the value to a function’s name. When you reference a function without arguments or parenthesis, it displays documentation. ( It’s mostly the same as the online docs )

Where does this come from? A lot of it is generated by metadata on the function’s type itself.

Let’s start drilling down. Using the function Value.Type you can view the type’s definition

It doesn’t seem very useful at first. The data we want is from the metadata, the Ascribed types.

Metadata of the function type

The first level describes the function using specific field names that the UI looks for . The UI renders some Html from the [Documentation.LongDescription] value.

You can drill down to [Documentation.Examples] , which is a list of records.

Viewing Documenation.Examples

FunctionParameters Types

There can be data defined for the arguments themselves. Parameters that are type any may have more information in their metadata.

Parameters’s may have metadata
Sometimes the metadata, of a parameter’s metadata — has more metadata!

Your First Function types

How do you document your own functions? Here’s a medium example. The function declared further below starts with this definition:

Text.ReplacePartialMatches_impl = (
        source as text, mapping as table
    ) as text => ...

To create the type, you start your function type almost the exact same as the definition. Then wrap it inside a type function

Text.ReplacePartialMatches.Type = type function(
        source as text,
        mapping as table
    ) as text meta [ .. ]

Next you start adding records to the final type’s metadata. If you haven’t seen the meta operator, check out Ben’s series:

The part that comes after meta operator is a regular record

let
    Text.ReplacePartialMatches = Value.ReplaceType( Text.ReplacePartialMatches_impl, Text.ReplacePartialMatches.Type ),
    Text.ReplacePartialMatches.Type = type function(
        source as text,
        mapping as Table.Type
    ) as text meta [
        Documentation.Name = "Text.ReplacePartialMatches",
        Documentation.LongDescription = Text.Combine({
            "Test strings for partial text matches. Replace the entire cell/value with the new replacement text.",
            "",
            "Mapping table requires two columns: <code>[Partial]</code> and <code>[New Value]</code> "

        }, "<br>")
    ],

    Text.ReplacePartialMatches_impl = ( source as text, mapping as table ) as text =>
        // todo: performance, exit early on first replacement
        let
            mappingList = Table.ToRecords( mapping ),
            result = List.Accumulate(
                mappingList,
                source,
                (state, cur) =>
                    if Text.Contains( state, cur[Partial], Comparer.OrdinalIgnoreCase )
                    then cur[New Value] else state
            )
        in result

in
    Text.ReplacePartialMatches

Query For the Screenshot

let
    Custom1 = Value.Type( Value.Type( Table.FromRecords ) ),
    fn_typeMeta = Value.Metadata( Value.Type( Table.FromRecords ) ),
    fn_typeMeta_example = ( Value.Metadata( Value.Type( Table.FromRecords ) )[Documentation.Examples]){1},
    t_fnParams = Type.FunctionParameters( Value.Type( Table.FromRecords ) ),
    fn_metaType = Value.Metadata( Type.FunctionParameters( Value.Type( Table.FromRecords ) ) ),
    type_ofFuncType = Value.Type( Type.FunctionParameters( Value.Type( Table.FromRecords ) ) [missingField] ),
    type_param_ofFuncType = Value.Metadata( Type.FunctionParameters( Value.Type( Table.FromRecords ) )[missingField] ),
    required_ofFuncType = Type.FunctionRequiredParameters( Value.Type( Table.FromRecords ) ) ,
    type_ofRequiredType = Value.Type( Type.FunctionRequiredParameters( Value.Type( Table.FromRecords ) ) ),
    type_ofType_ofRequiredType = Value.Metadata( Value.Type( Type.FunctionRequiredParameters( Value.Type( Table.FromRecords ) ) ) )
    
in
    type_ofType_ofRequiredType

See More

Functions

Categories
Command Line Experiment Formatting

Experiments of 2022-09

Power BI / Power Query

Things to note

  • options is an record, when used this way it’s similar to Python’s kwargs
  • Merging two records with update the existing fields, adding new fields, if they do not yet exist
  • (in PowerQuery) the order of steps don’t change the final result (order of execution is the same) That’s why defaults after config works
  • Sometimes readability improves when placing large “blocks” like values_list out of order so the logic is on top
  • I replaced values *before* converting them to text so you have more control (before coercion )
Text.JoinSpecialValues_impl = (source as list, optional options as nullable record) as text =>
    let
            config = Record.Combine({defaults, options ?? []}),
            defaults = [
                Separator = "|",
                UseSpecialSymbols = true
            ],
            text_list = List.Transform( values_list, Text.From),
            joined_string =  Text.Combine( text_list, config[Separator] ),
            values_list  = if not config[UseSpecialSymbols] then source else
                List.ReplaceMatchingItems( source,
                    {
                        // replace true null, and true empty strings (vs whitespace)
                        { null, "␀"},
                        { "#(cr,lf)", "#(240d)␤" }, // is #(2424)" }
                        { "#(lf)", "␤" }, // is #(2424)" }
                        {"", "␠"}
                    } ) 

        in
            joined_string,
Power Query and Report.pbix (permalink) at github://ninmonkey

Powershell

Goto Everything

Goto /c/foo/bar

# go back
> Goto -Back
> Goto '-'    # normal cd history works too
> Goto '+'

# Goto the world
$Profile            | goto  # go to string's path
Get-Item $PROFILE   | goto  # cd to the FileItem's path
gcm EditFunc        | goto  # jump to function declaration
gmo NameIt          | Goto  # go to module's folder
[CompletionResult]  | goto  # to docs for
# <https://docs.microsoft.com/en-us/dotnet/api/System.Management.Automation.CompletionResult>

# Open git repos in browser
goto git microsoft/powerquery-parser | goto
goto git@github.com:microsoft/powerquery-parser.git | goto 

# goto the newest log
Get-ChildItem 'c:\root\manyLogs' -Recurse
| Sort LastWriteTime -desc -top 1 | goto

Pwsh Cli

Display all parameters
My favorite hotkey, ctrl+spacebar

s

Breaking Formatting

2, 40, 100, 200, 400, <#700, 2000,#> 20000 | %{ $i=$_;
  0..10 | %{ $j = $_;
    0..3000 | Get-Random -Count 300 | %{ $k = $_
      [pscustomobject]@{ DisplayString = [string]$_ }} | fw -Column $i }
        "Was: $i"
        sleep -sec 0.7 }

Is it a bug, or, is the extra y-axis padding working as intended in a situation where intended is not intended ( ie: column count orders of magnitude larger than the terminal’s column count )

Excel functions: What’s New

https://insider.office.com/en-us/blog/text-and-array-manipulation-functions-in-excel

  • [ ] new array ops, make a query like
  • = a1: e1 , except new functions could dynamically change the selection based on variable