From 3051a367b9de59787c2de7600420d3da378946da Mon Sep 17 00:00:00 2001
From: stakx <stakx@eml.cc>
Date: Sat, 2 May 2020 12:07:06 +0200
Subject: [PATCH] Prefer to run `mono` via Docker

This lets us choose which version of Mono to use without having to
install it.

This is important because the version currently preinstalled on App-
Veyor has a regression that breaks our build, and installing another
Mono version on AppVeyor is both slow and error-prone.
---
 README.md                       |  2 +-
 appveyor.yml                    |  1 -
 build.sh                        | 16 ++++++++++++----
 buildscripts/docker-run-mono.sh |  4 ++++
 4 files changed, 17 insertions(+), 6 deletions(-)
 create mode 100755 buildscripts/docker-run-mono.sh

diff --git a/README.md b/README.md
index d445dc1c3d..562b145ce0 100644
--- a/README.md
+++ b/README.md
@@ -48,7 +48,7 @@ Most of these requirements should be covered by Visual Studio 2017.
 
 Compilation requires an up-to-date .NET Core SDK.
 
-Running the unit tests additionally requires Mono and the .NET Core 1.1 runtime to be installed. We recommend Mono 5.10+, though older versions (4.6.1+) might still work as well.
+Running the unit tests additionally requires the .NET Core 1.1 runtime to be installed, as well as either Docker or Mono. For the latter, we recommend Mono 5.10+, though older versions (4.6.1+) might still work as well.
 
 :information_source: **Mono runtime support:** Castle Core runs with minor limitations and defects on Mono 4.0.2+ (however 4.6.1+ is highly recommended, or 5.10+ if your code uses new C# 7.x language features such as `in` parameters).
 
diff --git a/appveyor.yml b/appveyor.yml
index 926c93a873..5428d4f4f8 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -21,7 +21,6 @@ for:
   # build and run tests
   build_script:
   - uname -a
-  - mono --version
   - ./build.sh
 
   # upload test results
diff --git a/build.sh b/build.sh
index 03519c913e..eea56cc55d 100755
--- a/build.sh
+++ b/build.sh
@@ -13,19 +13,27 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ****************************************************************************
+shopt -s expand_aliases
 
 DOTNETPATH=$(which dotnet)
 if [ ! -f "$DOTNETPATH" ]; then
 	echo "Please install Microsoft/netcore from: https://www.microsoft.com/net/core"
 	exit 1
 fi
-MONOPATH=$(which mono)
 
-if [ ! -f "$MONOPATH" ]; then
-	echo "Please install Xamarin/mono from: http://www.mono-project.com/docs/getting-started/install/"
-	exit 1
+DOCKERPATH=$(which docker)
+if [ -f "$DOCKERPATH" ]; then
+	alias mono="$PWD/buildscripts/docker-run-mono.sh"
+else
+	MONOPATH=$(which mono)
+	if [ ! -f "$MONOPATH" ]; then
+		echo "Please install either Docker, or Xamarin/Mono from http://www.mono-project.com/docs/getting-started/install/"
+		exit 1
+	fi
 fi
 
+mono --version
+
 # Linux/Darwin
 OSNAME=$(uname -s)
 echo "OSNAME: $OSNAME"
diff --git a/buildscripts/docker-run-mono.sh b/buildscripts/docker-run-mono.sh
new file mode 100755
index 0000000000..eb4459f8fd
--- /dev/null
+++ b/buildscripts/docker-run-mono.sh
@@ -0,0 +1,4 @@
+#!/bin/bash
+set -e
+MONO_TAG=${MONO_TAG:-6.0.0.334}
+docker run --rm -v "$PWD":'/project' -w='/project' mono:$MONO_TAG mono "$@"