Example of an expandable code block in an issue

[int3h]

When you have a long block of code (or other text) in an issue that you don't want to clutter up the page with, you can use an expandable code block.

To do so, you use the standard HTML5 <details> and tags <summary> tags. <summary> contains the placeholder line the user clicks to expand, and the subsequent content inside the <details> is the content shown when expanded (text or MarkDown content). GitHub allows you to just write HTML tags in your markdown, and will embed them in the rendered HTML as-is (assuming they're not a security vulnerability).

Example:

<details>
<summary>This line of text is the placeholder that a user can click to expand the full block</summary>
```cpp
/*
 * Copyright (C) 2014 Apple Inc. All rights reserved.
 *
...(a ton of text follows)...
```
</details>

This line of text is the placeholder that a user can click to expand the full block

/*
 * Copyright (C) 2014 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "ContentExtensionsBackend.h"

#if ENABLE(CONTENT_EXTENSIONS)

#include "CompiledContentExtension.h"
#include "ContentExtension.h"
#include "ContentExtensionsDebugging.h"
#include "DFABytecodeInterpreter.h"
#include "Document.h"
#include "DocumentLoader.h"
#include "ExtensionStyleSheets.h"
#include "Frame.h"
#include "FrameLoaderClient.h"
#include "MainFrame.h"
#include "ResourceLoadInfo.h"
#include "URL.h"
#include "UserContentController.h"
#include <wtf/NeverDestroyed.h>
#include <wtf/text/CString.h>

namespace WebCore {

namespace ContentExtensions {

void ContentExtensionsBackend::addContentExtension(const String& identifier, RefPtr<CompiledContentExtension> compiledContentExtension)
{
    ASSERT(!identifier.isEmpty());
    if (identifier.isEmpty())
        return;

    if (!compiledContentExtension) {
        removeContentExtension(identifier);
        return;
    }

    RefPtr<ContentExtension> extension = ContentExtension::create(identifier, adoptRef(*compiledContentExtension.leakRef()));
    m_contentExtensions.set(identifier, WTFMove(extension));
}

void ContentExtensionsBackend::removeContentExtension(const String& identifier)
{
    m_contentExtensions.remove(identifier);
}

void ContentExtensionsBackend::removeAllContentExtensions()
{
    m_contentExtensions.clear();
}

Vector<Action> ContentExtensionsBackend::actionsForResourceLoad(const ResourceLoadInfo& resourceLoadInfo) const
{
#if CONTENT_EXTENSIONS_PERFORMANCE_REPORTING
    double addedTimeStart = monotonicallyIncreasingTime();
#endif
    if (resourceLoadInfo.resourceURL.protocolIsData())
        return Vector<Action>();

    const String& urlString = resourceLoadInfo.resourceURL.string();
    ASSERT_WITH_MESSAGE(urlString.containsOnlyASCII(), "A decoded URL should only contain ASCII characters. The matching algorithm assumes the input is ASCII.");
    const CString& urlCString = urlString.utf8();

    Vector<Action> finalActions;
    ResourceFlags flags = resourceLoadInfo.getResourceFlags();
    for (auto& contentExtension : m_contentExtensions.values()) {
        RELEASE_ASSERT(contentExtension);
        const CompiledContentExtension& compiledExtension = contentExtension->compiledExtension();

        DFABytecodeInterpreter withoutDomainsInterpreter(compiledExtension.filtersWithoutDomainsBytecode(), compiledExtension.filtersWithoutDomainsBytecodeLength());
        DFABytecodeInterpreter::Actions withoutDomainsActions = withoutDomainsInterpreter.interpret(urlCString, flags);

        String domain = resourceLoadInfo.mainDocumentURL.host();
        DFABytecodeInterpreter withDomainsInterpreter(compiledExtension.filtersWithDomainsBytecode(), compiledExtension.filtersWithDomainsBytecodeLength());
        DFABytecodeInterpreter::Actions withDomainsActions = withDomainsInterpreter.interpretWithDomains(urlCString, flags, contentExtension->cachedDomainActions(domain));

        const SerializedActionByte* actions = compiledExtension.actions();
        const unsigned actionsLength = compiledExtension.actionsLength();

        bool sawIgnorePreviousRules = false;
        const Vector<uint32_t>& universalWithDomains = contentExtension->universalActionsWithDomains(domain);
        const Vector<uint32_t>& universalWithoutDomains = contentExtension->universalActionsWithoutDomains();
        if (!withoutDomainsActions.isEmpty() || !withDomainsActions.isEmpty() || !universalWithDomains.isEmpty() || !universalWithoutDomains.isEmpty()) {
            Vector<uint32_t> actionLocations;
            actionLocations.reserveInitialCapacity(withoutDomainsActions.size() + withDomainsActions.size() + universalWithoutDomains.size() + universalWithDomains.size());
            for (uint64_t actionLocation : withoutDomainsActions)
                actionLocations.uncheckedAppend(static_cast<uint32_t>(actionLocation));
            for (uint64_t actionLocation : withDomainsActions)
                actionLocations.uncheckedAppend(static_cast<uint32_t>(actionLocation));
            for (uint32_t actionLocation : universalWithoutDomains)
                actionLocations.uncheckedAppend(actionLocation);
            for (uint32_t actionLocation : universalWithDomains)
                actionLocations.uncheckedAppend(actionLocation);
            std::sort(actionLocations.begin(), actionLocations.end());

            // Add actions in reverse order to properly deal with IgnorePreviousRules.
            for (unsigned i = actionLocations.size(); i; i--) {
                Action action = Action::deserialize(actions, actionsLength, actionLocations[i - 1]);
                action.setExtensionIdentifier(contentExtension->identifier());
                if (action.type() == ActionType::IgnorePreviousRules) {
                    sawIgnorePreviousRules = true;
                    break;
                }
                finalActions.append(action);
            }
        }
        if (!sawIgnorePreviousRules) {
            finalActions.append(Action(ActionType::CSSDisplayNoneStyleSheet, contentExtension->identifier()));
            finalActions.last().setExtensionIdentifier(contentExtension->identifier());
        }
    }
#if CONTENT_EXTENSIONS_PERFORMANCE_REPORTING
    double addedTimeEnd = monotonicallyIncreasingTime();
    dataLogF("Time added: %f microseconds %s \n", (addedTimeEnd - addedTimeStart) * 1.0e6, resourceLoadInfo.resourceURL.string().utf8().data());
#endif
    return finalActions;
}

StyleSheetContents* ContentExtensionsBackend::globalDisplayNoneStyleSheet(const String& identifier) const
{
    const auto& contentExtension = m_contentExtensions.get(identifier);
    return contentExtension ? contentExtension->globalDisplayNoneStyleSheet() : nullptr;
}

BlockedStatus ContentExtensionsBackend::processContentExtensionRulesForLoad(ResourceRequest& request, ResourceType resourceType, DocumentLoader& initiatingDocumentLoader)
{
    if (m_contentExtensions.isEmpty())
        return BlockedStatus::NotBlocked;

    Document* currentDocument = nullptr;
    URL mainDocumentURL;

    if (Frame* frame = initiatingDocumentLoader.frame()) {
        currentDocument = frame->document();

        if (initiatingDocumentLoader.isLoadingMainResource()
            && frame->isMainFrame()
            && resourceType == ResourceType::Document)
            mainDocumentURL = request.url();
        else if (Document* mainDocument = frame->mainFrame().document())
            mainDocumentURL = mainDocument->url();
    }

    ResourceLoadInfo resourceLoadInfo = { request.url(), mainDocumentURL, resourceType };
    Vector<ContentExtensions::Action> actions = actionsForResourceLoad(resourceLoadInfo);

    bool willBlockLoad = false;
    for (const auto& action : actions) {
        switch (action.type()) {
        case ContentExtensions::ActionType::BlockLoad:
            willBlockLoad = true;
            break;
        case ContentExtensions::ActionType::BlockCookies:
            request.setAllowCookies(false);
            break;
        case ContentExtensions::ActionType::CSSDisplayNoneSelector:
            if (resourceType == ResourceType::Document)
                initiatingDocumentLoader.addPendingContentExtensionDisplayNoneSelector(action.extensionIdentifier(), action.stringArgument(), action.actionID());
            else if (currentDocument)
                currentDocument->extensionStyleSheets().addDisplayNoneSelector(action.extensionIdentifier(), action.stringArgument(), action.actionID());
            break;
        case ContentExtensions::ActionType::CSSDisplayNoneStyleSheet: {
            StyleSheetContents* styleSheetContents = globalDisplayNoneStyleSheet(action.stringArgument());
            if (styleSheetContents) {
                if (resourceType == ResourceType::Document)
                    initiatingDocumentLoader.addPendingContentExtensionSheet(action.stringArgument(), *styleSheetContents);
                else if (currentDocument)
                    currentDocument->extensionStyleSheets().maybeAddContentExtensionSheet(action.stringArgument(), *styleSheetContents);
            }
            break;
        }
        case ContentExtensions::ActionType::MakeHTTPS: {
            const URL originalURL = request.url();
            if (originalURL.protocolIs("http") && (!originalURL.hasPort() || isDefaultPortForProtocol(originalURL.port(), originalURL.protocol()))) {
                URL newURL = originalURL;
                newURL.setProtocol("https");
                if (originalURL.hasPort())
                    newURL.setPort(defaultPortForProtocol("https"));
                request.setURL(newURL);

                if (resourceType == ResourceType::Document && initiatingDocumentLoader.isLoadingMainResource()) {
                    // This is to make sure the correct 'new' URL shows in the location bar.
                    initiatingDocumentLoader.request().setURL(newURL);
                    initiatingDocumentLoader.frameLoader()->client().dispatchDidChangeProvisionalURL();
                }
                if (currentDocument)
                    currentDocument->addConsoleMessage(MessageSource::ContentBlocker, MessageLevel::Info, makeString("Content blocker promoted URL from ", originalURL.string(), " to ", newURL.string()));
            }
            break;
        }
        case ContentExtensions::ActionType::IgnorePreviousRules:
        case ContentExtensions::ActionType::InvalidAction:
            RELEASE_ASSERT_NOT_REACHED();
        }
    }

    if (willBlockLoad) {
        if (currentDocument)
            currentDocument->addConsoleMessage(MessageSource::ContentBlocker, MessageLevel::Info, makeString("Content blocker prevented frame displaying ", mainDocumentURL.string(), " from loading a resource from ", request.url().string()));
        return BlockedStatus::Blocked;
    }
    return BlockedStatus::NotBlocked;
}

const String& ContentExtensionsBackend::displayNoneCSSRule()
{
    static NeverDestroyed<const String> rule(ASCIILiteral("display:none !important;"));
    return rule;
}

} // namespace ContentExtensions

} // namespace WebCore

#endif // ENABLE(CONTENT_EXTENSIONS)