Xamarin.forms: [Bug] XAMLC breaks if Binding contains apostrophe " ' " [V4.5.0 Pre Release 1]

[JKennedy24]

Breaks with V4.5.0 Pre Release 1

Description

I have a binding like so:

Colors="{styling:ColorList 'AccentButtonTextColour' }"

but I get the error:

Empty value string in markup expression

I could remove the apostrophes, but If I have a binding with a comma in it then I can't like so:

Colors="{styling:ColorList 'AccentButtonTextColour,AccentButtonTextColour2' }"

Works again if I downgrade to stable

[StephaneDelcroix]

please provide your markup extension code. thanks

[JKennedy24]

@StephaneDelcroix

My Markup code is:

[ContentProperty("Text")]
public class ColorListExtension : IMarkupExtension
{
    public string Text { get; set; }

    //This errors on a page "Specified Cast is invalid". and doesnt work in a style
    public object ProvideValue(IServiceProvider serviceProvider)
    {
        if (Text == null)
            throw new Exception("No Colors Provided");

        return StylingLookup.GetColorList(Text);
    }
}

[JKennedy24]

extra info: think this happens more when the extension is used on the property of a control in a datatemplate?

[JKennedy24]

BTW this is also a regression from 4.4.0. May help when triaging

[dirivero]

This also prevents from using StringFormat in bindings:

<Label Text="{Binding Amount, StringFormat='$ {0}'}" />

[solomonfried]

One way around this issue is to use a String Resource in your XAML
For my case where I had
<ColumnDefinition Width="{Binding IsDashboardFullScreen, Converter={StaticResource BoolToGridLengthConverter}, ConverterParameter='0,1'}" />

I was able to replace it with
```

```

[StephaneDelcroix]

I'm unable to reproduce this issue on 4.4.0 (as expected), 4.5.0-pre1 or the HEAD of the 4.5.0 branch.

I pushed a unit test for this on the 4.5.0 branch https://github.com/xamarin/Xamarin.Forms/commit/8205d408462aa7a5f6f2e99936640fa2fb98b73e

@JKennedy24 @dirivero if you think this bug still exists, I'd need a small and contained reproduction project for it. Thanks.

[dirivero]

@StephaneDelcroix it only happens with 4.5. In previous versions it did work as far as I know.

I've run a few more tests because I couldn't reproduce the issue with my own sample Label above (sorry about that). I've found that the problem happens if you add a white space after the '.

Works:

<Label Text="{Binding Amount, StringFormat='$ {0}'}" />

Doesn't work (error: Empty value string in markup expression)

<Label Text="{Binding Amount, StringFormat='$ {0}' }" />

It also fails with a new line (the one after 'iOS'):

    <Label Text="{
        OnPlatform
            Android='android',
            iOS='iOS'
        }" />

If you update your test case XAML code by adding a white space at the end it should fail as well:

<Label x:Name="label" Text="{local:Gh9212Markup 'Foo, Bar' }" />

Repro project here Issue9212.zip

Thanks!

[JKennedy24]

@dirivero It could be the added whitespace that is causing it! I could never work out why some views were fine and others wouldn't compile.

Only happened on version greater than 4.5.0-Pre1

[solomonfried]

@dirivero It could be the added whitespace that is causing it! I could never work out why some views were fine and others wouldn't compile.
Only happened on version greater than 4.5.0-Pre1

Whitespace seems to be the issue. Great catch!!!

This fails (note the space between the end apostrophe and the last closing bracket)
<ColumnDefinition Width="{Binding IsDashboardFullScreen, Converter={StaticResource BoolToGridLengthConverter}, ConverterParameter='0,*' }"

This works!
<ColumnDefinition Width="{Binding IsDashboardFullScreen, Converter={StaticResource BoolToGridLengthConverter}, ConverterParameter='0,*'}"

[StephaneDelcroix]

thx for the additional tests @dirivero, the trailing space is indeed what causes the issue. working on it

[StephaneDelcroix]

bug introduced by #8980

[tossingc]

@StephaneDelcroix Thank you for addressing this! Two questions:

1. will this fix also address line breaks in binding definitions?
   _I need to upgrade to XF 4.5, but most of my Bindings are defined using line breaks to increase trackability of changes within the individual binding properties_
2. when will this be released to NuGet?

[hitaspdotnet]

When will this be released to NuGet?

[tossingc]

Confirmed fix is out in 4.5.0-sr2 (4.5.0.495 out on nuget)! 🙌
https://docs.microsoft.com/en-us/xamarin/xamarin-forms/release-notes/4.5/4.5.0-sr2

And yes, it does also handle newlines. 😊

Thanks @StephaneDelcroix !