How to use StoreRequest method of PuppeteerSharp.NetworkEventManager class

Ok, turns out it was a mix of things. The dockerfile needed rearranging and works best without a sandbox. As you'll see, the original code was installing dependencies on the intermediate image rather then the final/base.

For some reason, I couldn't get it to work under a sandboxed user properly, so that was removed. As a result the implementation needed updating to enable the --no-sandbox argument.

Here's the updated code for anyone else struggling to get puppeteer-sharp working with .NET Core 3.1.

dockerfile

#See https://aka.ms/containerfastmode to understand how Visual Studio uses this Dockerfile to build your images for faster debugging.

FROM mcr.microsoft.com/dotnet/core/aspnet:3.1-buster-slim AS base
#####################
#PUPPETEER RECIPE
#####################
# Install latest chrome dev package and fonts to support major charsets (Chinese, Japanese, Arabic, Hebrew, Thai and a few others)
# Note: this installs the necessary libs to make the bundled version of Chromium that Puppeteer
# installs, work.
ARG CHROME_VERSION="81.0.4044.138-1"
RUN apt-get update && apt-get -f install && apt-get -y install wget gnupg2 apt-utils
RUN wget --no-verbose -O /tmp/chrome.deb http://dl.google.com/linux/chrome/deb/pool/main/g/google-chrome-stable/google-chrome-stable_${CHROME_VERSION}_amd64.deb \
&& apt-get update \
&& apt-get install -y /tmp/chrome.deb --no-install-recommends --allow-downgrades fonts-ipafont-gothic fonts-wqy-zenhei fonts-thai-tlwg fonts-kacst fonts-freefont-ttf \
&& rm /tmp/chrome.deb

ENV PUPPETEER_EXECUTABLE_PATH "/usr/bin/google-chrome"
#####################
#END PUPPETEER RECIPE
#####################

WORKDIR /app
EXPOSE 80
EXPOSE 443


FROM mcr.microsoft.com/dotnet/core/sdk:3.1-buster AS build
WORKDIR /src


COPY ["ProjectName.Core/ProjectName.Core.csproj", "ProjectName.Core/"]
RUN dotnet restore "ProjectName.Core/ProjectName.Core.csproj"


COPY . .
WORKDIR "/src/ProjectName.Core"
RUN dotnet build "ProjectName.Core.csproj" -c Release -o /app/build

FROM build AS publish
RUN dotnet publish "ProjectName.Core.csproj" -c Release -o /app/publish

FROM base AS final
WORKDIR /app
COPY --from=publish /app/publish .
ENTRYPOINT ["dotnet", "ProjectName.Core.dll"]

Implementation

public static async Task<Stream> GeneratePdfFromHtml(string html, List<string> styleUrls = null)
{
    await new BrowserFetcher().DownloadAsync(BrowserFetcher.DefaultRevision);

    var browser = await Puppeteer.LaunchAsync(new LaunchOptions
    {
        Args = new[] { "--no-sandbox" },
        Headless = true                
    });

    using (var page = await browser.NewPageAsync())
    {
        await page.SetContentAsync(html);

        if(styleUrls != null)
            foreach (var url in styleUrls)
            {
                await page.AddStyleTagAsync(new AddTagOptions { Path = url });
            }

        return await page.PdfStreamAsync();                
    }
}

It's probably worth noting that the docker implementation of puppeteer-sharp also seems to have a problem with finding stylesheets using a local url (e.g. localhost:1234/lib/bootsrap/bootsrap.min.css). It just hangs and spins forever, hence changing the AddStyleTagAsync() to use filepaths instead. Don't forget, this is found under IHostingEnvironment.WebRootPath to save you a google search.

Hope this helps someone else out there. No doubt it'll cross my path again at some point in the not-so-distant future too!