Revert "Revert QgsBlockingNetworkRequest"

With recent changes in QgsNetworkAccessManager this should be
safe to resurrect (fingers crossed!). Also simplify code a lot,
because now QgsNetworkAccessManager handles waking the worker
thread after the auth request is handled.

Add a lot more tests

python/core/auto_generated/qgsblockingnetworkrequest.sip.in

@@ -0,0 +1,146 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsblockingnetworkrequest.h                                 *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+class QgsBlockingNetworkRequest : QObject
+{
+%Docstring
+A thread safe class for performing blocking (sync) network requests, with full support for QGIS proxy
+and authentication settings.
+
+This class should be used whenever a blocking network request is required. Unlike implementations
+which rely on QApplication.processEvents() or creation of a QEventLoop, this class is completely
+thread safe and can be used on either the main thread or background threads without issue.
+
+Redirects are automatically handled by the class.
+
+After completion of a request, the reply content should be retrieved by calling getReplyContent().
+This method returns a QgsNetworkReplyContent container, which is safe and cheap to copy and pass
+between threads without issue.
+
+.. versionadded:: 3.6
+%End
+
+%TypeHeaderCode
+#include "qgsblockingnetworkrequest.h"
+%End
+  public:
+
+    enum ErrorCode
+    {
+      NoError,
+      NetworkError,
+      TimeoutError,
+      ServerExceptionError,
+    };
+
+    explicit QgsBlockingNetworkRequest();
+%Docstring
+Constructor for QgsBlockingNetworkRequest
+%End
+
+    ~QgsBlockingNetworkRequest();
+
+    ErrorCode get( QNetworkRequest &request, bool forceRefresh = false, QgsFeedback *feedback = 0 );
+%Docstring
+Performs a "get" operation on the specified ``request``.
+
+If ``forceRefresh`` is false then previously cached replies may be used for the request. If
+it is set to true then a new query is always performed.
+
+If an authCfg() has been set, then any authentication configuration required will automatically be applied to
+``request``. There is no need to manually apply the authentication to the request prior to calling
+this method.
+
+The optional ``feedback`` argument can be used to abort ongoing requests.
+
+The method will return NoError if the get operation was successful. The contents of the reply can be retrieved
+by calling reply().
+
+If an error was encountered then a specific ErrorCode will be returned, and a detailed error message
+can be retrieved by calling errorMessage().
+
+.. seealso:: :py:func:`post`
+%End
+
+    ErrorCode post( QNetworkRequest &request, const QByteArray &data, bool forceRefresh = false, QgsFeedback *feedback = 0 );
+%Docstring
+Performs a "post" operation on the specified ``request``, using the given ``data``.
+
+If ``forceRefresh`` is false then previously cached replies may be used for the request. If
+it is set to true then a new query is always performed.
+
+If an authCfg() has been set, then any authentication configuration required will automatically be applied to
+``request``. There is no need to manually apply the authentication to the request prior to calling
+this method.
+
+The optional ``feedback`` argument can be used to abort ongoing requests.
+
+The method will return NoError if the get operation was successful. The contents of the reply can be retrieved
+by calling reply().
+
+If an error was encountered then a specific ErrorCode will be returned, and a detailed error message
+can be retrieved by calling errorMessage().
+
+.. seealso:: :py:func:`get`
+%End
+
+    QString errorMessage() const;
+%Docstring
+Returns the error message string, after a get() or post() request has been made.\
+%End
+
+    QgsNetworkReplyContent reply() const;
+%Docstring
+Returns the content of the network reply, after a get() or post() request has been made.
+%End
+
+    QString authCfg() const;
+%Docstring
+Returns the authentication config id which will be used during the request.
+
+.. seealso:: :py:func:`setAuthCfg`
+%End
+
+    void setAuthCfg( const QString &authCfg );
+%Docstring
+Sets the authentication config id which should be used during the request.
+
+.. seealso:: :py:func:`authCfg`
+%End
+
+  public slots:
+
+    void abort();
+%Docstring
+Aborts the network request immediately.
+%End
+
+  signals:
+
+    void downloadProgress( qint64, qint64 );
+%Docstring
+Emitted when when data arrives during a request.
+%End
+
+    void downloadFinished();
+%Docstring
+Emitted once a request has finished downloading.
+%End
+
+};
+
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsblockingnetworkrequest.h                                 *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/core/auto_generated/qgsnetworkaccessmanager.sip.in

@@ -11,6 +11,7 @@
 
 
 
+
 class QgsNetworkRequestParameters
 {
 %Docstring
@@ -251,6 +252,52 @@ Sets the maximum timeout ``time`` for network requests, in milliseconds.
 
 .. seealso:: :py:func:`timeout`
 
+.. versionadded:: 3.6
+%End
+
+    static QgsNetworkReplyContent blockingGet( QNetworkRequest &request, const QString &authCfg = QString(), bool forceRefresh = false, QgsFeedback *feedback = 0 );
+%Docstring
+Posts a GET request to obtain the contents of the target request and returns a new QgsNetworkReplyContent object for reading.
+The current thread will be blocked until the request is returned.
+
+This method is safe to call in either the main thread or a worker thread.
+
+If ``forceRefresh`` is false then previously cached replies may be used for the request. If
+it is set to true then a new query is always performed.
+
+If an ``authCfg`` has been specified, then that authentication configuration required will automatically be applied to
+``request``. There is no need to manually apply the authentication to the request prior to calling
+this method.
+
+The optional ``feedback`` argument can be used to abort ongoing requests.
+
+The contents of the reply will be returned after the request is completed or an error occurs.
+
+.. seealso:: :py:func:`blockingPost`
+
+.. versionadded:: 3.6
+%End
+
+    static QgsNetworkReplyContent blockingPost( QNetworkRequest &request, const QByteArray &data, const QString &authCfg = QString(), bool forceRefresh = false, QgsFeedback *feedback = 0 );
+%Docstring
+Posts a POST request to obtain the contents of the target ``request``, using the given ``data``, and returns a new
+QgsNetworkReplyContent object for reading. The current thread will be blocked until the request is returned.
+
+This method is safe to call in either the main thread or a worker thread.
+
+If ``forceRefresh`` is false then previously cached replies may be used for the request. If
+it is set to true then a new query is always performed.
+
+If an ``authCfg`` has been specified, then that authentication configuration required will automatically be applied to
+``request``. There is no need to manually apply the authentication to the request prior to calling
+this method.
+
+The optional ``feedback`` argument can be used to abort ongoing requests.
+
+The contents of the reply will be returned after the request is completed or an error occurs.
+
+.. seealso:: :py:func:`blockingGet`
+
 .. versionadded:: 3.6
 %End
 

python/core/auto_generated/qgsnetworkreply.sip.in

@@ -109,6 +109,10 @@ Returns the unique ID identifying the original request which this response was f
 Returns the original network request.
 %End
 
+    void setContent( const QByteArray &content );
+
+    QByteArray content() const;
+
 };
 
 /************************************************************************

python/core/core_auto.sip

@@ -318,6 +318,7 @@
 %Include auto_generated/qgsactionscoperegistry.sip
 %Include auto_generated/qgsanimatedicon.sip
 %Include auto_generated/qgsauxiliarystorage.sip
+%Include auto_generated/qgsblockingnetworkrequest.sip
 %Include auto_generated/qgsbrowsermodel.sip
 %Include auto_generated/qgsbrowserproxymodel.sip
 %Include auto_generated/qgscoordinatereferencesystem.sip

src/app/qgisapp.cpp

@@ -1589,6 +1589,10 @@ QgisApp::~QgisApp()
   qDeleteAll( mCustomDropHandlers );
   qDeleteAll( mCustomLayoutDropHandlers );
 
+  // replace gui based network access managers with failing only ones
+  QgsNetworkAccessManager::instance()->setSslErrorHandler( qgis::make_unique< QgsSslErrorHandler >() );
+  QgsNetworkAccessManager::instance()->setAuthHandler( qgis::make_unique< QgsNetworkAuthenticationHandler >() );
+
   const QList<QgsMapCanvas *> canvases = mapCanvases();
   for ( QgsMapCanvas *canvas : canvases )
   {

src/core/CMakeLists.txt

@@ -153,6 +153,7 @@ SET(QGIS_CORE_SRCS
   qgsattributeeditorelement.cpp
   qgsauxiliarystorage.cpp
   qgsbearingutils.cpp
+  qgsblockingnetworkrequest.cpp
   qgsbrowsermodel.cpp
   qgsbrowserproxymodel.cpp
   qgscachedfeatureiterator.cpp
@@ -602,6 +603,7 @@ SET(QGIS_CORE_MOC_HDRS
   qgsactionscoperegistry.h
   qgsanimatedicon.h
   qgsauxiliarystorage.h
+  qgsblockingnetworkrequest.h
   qgsbrowsermodel.h
   qgsbrowserproxymodel.h
   qgscoordinatereferencesystem.h