[reportlab-users] Fwd: [reportlab-support] ReportLab Pylance Bug

[Robin Becker]

-------- Forwarded Message --------
Subject: Re: [reportlab-support] ReportLab Pylance Bug
Date: Mon, 5 Sep 2022 10:15:10 +0100
From: Robin Becker <support at reportlab.com>
To: Natalie Jackson <jackson.natalie at gmail.com>
CC: For users of Reportlab open source software <reportlab-users at lists2.reportlab.com>

Hi Natalie,

thanks for the report, but as you note the conclusion drawn by Pylance is clearly wrong; perhaps there's something wrong 
with the instance of reportlab that you are running so that Pylance concludes there's always an exception thrown.


1) reportlab.graphics.renderbase.Renderer class implements undefined methods eg drawString

2) The function reportlab.graphics.renderPDF.draw is

     def draw(drawing, canvas, x, y, showBoundary=rl_config._unset_):
         """As it says"""
         R = _PDFRenderer()
         R.draw(renderScaledDrawing(drawing), canvas, x, y, showBoundary=showBoundary)

so it is using class reportlab.graphics.renderPDF._PDFRenderer.

3) class _PDFRenderer(Renderer):
        .......
inherits from reportlab.graphics.renderbase.Renderer, but as is expected this class does override all the needed methods 
including eg
	def drawString(self, stringObj):
		textRenderMode = getattr(stringObj,'textRenderMode',0)
		needFill = textRenderMode in (0,2,4,6)
		needStroke = textRenderMode in (1,2,5,6)
		.......

so as you find yourself there's no forced exception in renderbase.Renderer

It seems clear that the analysis of bschnurr is wrong. No decorator is needed on _PDFRenderer, standard python 
inheritance is sufficient.

If you wish to continue the discussion by all means do so, but please do so at the reportlab-users list which you can 
easily join at https://pairlist2.pair.net/mailman/listinfo/reportlab-users.
--
Robin Becker

On 01/09/2022 19:02, Natalie Jackson wrote:
> Hi,
> 
> When I call the method reportlab.graphics.renderPDF.draw(), Pylance in VS
> Code interprets the subsequent code as unreachable, though the subsequent
> code runs.
> 
> I posted this issue to Pylance issues on github, and a Microsoft member
> responded with some advice, including that I file an issue with the library
> maintainer, hence this message to you now.
> 
> Copied from https://github.com/microsoft/pylance-release/issues/3270 :
> natajacks <https://github.com/natajacks> commented 2 hours ago
> <https://github.com/microsoft/pylance-release/issues/3270#issue-1359059212>
> Environment data
> 
>     - Language Server version: 2022.8.50
>     - OS and version: Windows 10 Enterprise, Version 21H
>     - Python version (& distribution if applicable, e.g. Anaconda): 3.8.6
>     - reportlab version: 3.6.5 (pip install reportlab)
> 
> Code Snippet
> 
> from reportlab.graphics import renderPDF
> ...
> renderPDF.draw(
> my_reportlab_graphics_object,
> my_canvas,
> 70, # x pixels from left on pdf page (reportlab Canvas)
> 30 # y pixels from bottom on pdf page (reportlab Canvas)
> )
> 
> code_after_renderPDFdraw_marked_unreachable_but_it_runs()
> [image: @github-actions] <https://github.com/apps/github-actions>
> github-actions <https://github.com/apps/github-actions> bot added the
> triage-needed
> <https://github.com/microsoft/pylance-release/labels/triage-needed> label 2
> hours ago
> <https://github.com/microsoft/pylance-release/issues/3270#event-7306542796>
> [image: @bschnurr] <https://github.com/bschnurr>
> Member
> bschnurr <https://github.com/bschnurr> commented 1 hour ago
> <https://github.com/microsoft/pylance-release/issues/3270#issuecomment-1234531092>
>   •
> edited
> 
> thanks for the issue.
> 
> seems there are two class
> parent Renderer
> child _PDFRenderer
> 
> child's instance calls the parents draw, which calls applyStateChanges and
> the parent's version always throws an exception.
> 
> maybe _PDFRenderer is missing an @override decorator
> [image: @bschnurr] <https://github.com/bschnurr>
> Member
> bschnurr <https://github.com/bschnurr> commented 1 hour ago
> <https://github.com/microsoft/pylance-release/issues/3270#issuecomment-1234540153>
>   •
> edited
> 
> ah..
> 
> in renderbase.py
> 
> add @abstractmethod to
> 
> @abstractmethoddef drawNode(self, node):
> @abstractmethoddef applyStateChanges(self, delta, newState):
> 
> and any funciton that calls self.undefined("drawString")
> [image: @bschnurr] <https://github.com/bschnurr>
> Member
> bschnurr <https://github.com/bschnurr> commented 1 hour ago
> <https://github.com/microsoft/pylance-release/issues/3270#issuecomment-1234540949>
> 
> please file an issue with the library maintainer
> 
> 
> 
> 
> 
> 
> Let me know if I can provide more information, thanks,
> 
> 
> - Natalie
> 
> 
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