[build] Don't use ls(1) to find JDK paths

Fixes: dotnet/android#1493

On some machines, `make prepare` fails:

	build-tools/scripts/jdk.mk:130: *** missing separator.  Stop.
	make: *** [prepare-external] Error 2

Eventually, we "found" the "cause": This make fragment:

	$(shell ls -dtr $(_DARWIN_JDK_FALLBACK_DIRS) | sort | tail -1)

was dying a terrible horrible no good death:

	_DARWIN_JDK_ROOT=/Library/Java/JavaVirtualMachines/jdk1.8.0_161.jdk
	kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkin/sh: 49m: command not found

[Turns Out™][0], **ls**(1) should be *avoided*, as its output is
*unsafe* (I'm not sure *why*, and I'm not able to repro the above
failure on my machine, but it's *clearly* bad).

[0]: http://mywiki.wooledge.org/ParsingLs

Why are we using **ls**(1)?  To sort by timestamp, via `ls -dtr`.
What's the recommended replacement?

> If you truly need a list of all the files in a directory in order
> by mtime so that you can process them in sequence, switch to perl,
> and have your perl program do its own directory opening and sorting

LOL?

Which brings us to the solution: we don't want to use Perl -- we
*want* something plausibly cross-platform -- so let's use our existing
cross-platform dependency: MSBuild!

Add a new `<JdkDirectoryFinder/>` task, to which we provide a
"JDKs Root" directory -- the directory which contains JDKs -- and the
`<JdkDirectoryFinder/>` task will open that directory, sort the
contents, skip the "out of version range" JDK versions
(`$(JI_JDK_MAX)`; commit 55c56f7), and return the "best" JDK root
directory from those available.

Author: jonpryor

Makefile

@@ -53,7 +53,10 @@ xa-all: $(PACKAGES) $(XA_INTEGRATION_OUTPUTS)
 
 run-all-tests: run-tests run-test-jnimarshal run-test-generator-core run-ptests
 
-prepare:: prepare-external
+prepare:: prepare-bootstrap prepare-external
+
+prepare-bootstrap:
+	$(MSBUILD) $(MSBUILD_FLAGS) src/Java.Interop.BootstrapTasks/Java.Interop.BootstrapTasks.csproj
 
 prepare-external: $(PACKAGES) $(NUNIT_CONSOLE)
 	git submodule update --init --recursive
@@ -64,8 +67,8 @@ clean:
 	-rm src/Java.Runtime.Environment/Java.Runtime.Environment.dll.config
 
 include build-tools/scripts/mono.mk
-include build-tools/scripts/jdk.mk
 include build-tools/scripts/msbuild.mk
+include build-tools/scripts/jdk.mk
 
 $(PACKAGES) $(NUNIT_CONSOLE):
 	nuget restore

build-tools/scripts/jdk.mk

@@ -32,16 +32,6 @@ JI_JAR_PATH   = jar
 JI_JDK_BIN_PATH = $(dir $(shell which java))
 
 
-# Filter on <= JI_MAX_JDK
-ifneq ($(JI_MAX_JDK),)
-_VERSION_MAX  := | awk '$$1 <= $(JI_MAX_JDK)'
-endif #JI_MAX_JDK
-
-# Sort numerically on version numbers with `sort -n`, filtering on $(JI_MAX_JDK) if needed
-# Replace each line so it starts with a number (sed 's/...'\1 &/), sort on the leading number, then remove the leading number.
-# Grab the last path name printed.
-_VERSION_SORT := sed 's/[^0-9]*\([0-9.]*\)/\1 &/' $(_VERSION_MAX) | sort -n | sed 's/^[0-9.]* //g' | tail -1
-
 ifeq ($(OS),Darwin)
 
 _MONO_BITNESS = $(shell file `which $(word 1, $(RUNTIME))` | awk 'BEGIN { val = "32-bit" } /64-bit/ { val = "64-bit" } END { print val; }')
@@ -51,6 +41,12 @@ ifeq ($(_MONO_BITNESS),32-bit)
 JI_JVM_PATH	= /System/Library/Frameworks/JavaVM.framework/JavaVM
 endif # 32-bit
 
+# $(call FindJdkDirectory,dir)
+define FindJdkDirectory
+	$(MSBUILD) $(MSBUILD_FLAGS) build-tools/scripts/jdk.targets /nologo /v:minimal /t:GetPreferredJdkRoot \
+		/p:JdksRoot="$(1)" $(if $(JI_MAX_JDK),"/p:MaximumJdkVersion=$(JI_MAX_JDK)")
+endef
+
 # Darwin supports three possible search locations:
 #
 # 1. `/Library/Java/JavaVirtualMachines/jdk*`
@@ -62,7 +58,7 @@ endif # 32-bit
 #
 # 3. A "locally" hosted .pkg, in case Xcode.app isn't installed.
 
-_DARWIN_JDK_FALLBACK_DIRS         = $(wildcard /Library/Java/JavaVirtualMachines/jdk*)
+_DARWIN_JDK_FALLBACK_ROOT         = $(wildcard /Library/Java/JavaVirtualMachines)
 _DARWIN_JDK_JNI_INCLUDE_DIR       = Contents/Home/include
 _DARWIN_JDK_JNI_OS_INCLUDE_DIR    = $(_DARWIN_JDK_JNI_INCLUDE_DIR)/darwin
 
@@ -77,8 +73,8 @@ _LOCAL_JDK_HEADERS                = LocalJDK/System/Library/Frameworks/JavaVM.fr
 # Ancient source for (3)
 _APPLE_JDK6_URL                   = http://adcdownload.apple.com/Developer_Tools/java_for_os_x_2013005_developer_package/java_for_os_x_2013005_dp__11m4609.dmg
 
-ifneq ($(_DARWIN_JDK_FALLBACK_DIRS),)
-_DARWIN_JDK_ROOT      := $(shell ls -dtr $(_DARWIN_JDK_FALLBACK_DIRS) | $(_VERSION_SORT))
+ifneq ($(_DARWIN_JDK_FALLBACK_ROOT),)
+_DARWIN_JDK_ROOT      := $(shell $(call FindJdkDirectory,$(_DARWIN_JDK_FALLBACK_ROOT)) | tr -d '[[:space:]]')
 JI_JDK_BIN_PATH       = $(_DARWIN_JDK_ROOT)/Contents/Home/bin
 JI_JAVAC_PATH         = $(_DARWIN_JDK_ROOT)/Contents/Home/bin/javac
 JI_JAR_PATH           = $(_DARWIN_JDK_ROOT)/Contents/Home/bin/jar
@@ -117,7 +113,7 @@ ifeq ($(OS),Linux)
 # This is for all linux distributions with which and java installed
 _DEFAULT_LINUX_JAVA_ROOT          = $(shell java -XshowSettings:properties -help 2>&1 | grep java.home | sed 's/^.*java.home = //g')/../
 _DEFAULT_LINUX_JAVA_INCLUDE_DIRS  = $(_DEFAULT_LINUX_JAVA_ROOT)/include/
-_LINUX_JAVA_FALLBACK_DIRS         = /usr/lib/jvm/java*
+_LINUX_JAVA_FALLBACK_ROOT         = $(wildcard /usr/lib/jvm)
 _LINUX_JAVA_JNI_INCLUDE_DIR       = include
 _LINUX_JAVA_ROOT                  = $(_DEFAULT_LINUX_JAVA_ROOT)
 _LINUX_JAVA_ARCH_64               = amd64
@@ -130,8 +126,8 @@ _DESKTOP_JAVA_INCLUDE_DIRS  = $(wildcard $(JAVA_HOME)/include)
 _LINUX_JAVA_ROOT            = $(JAVA_HOME)
 endif # No default Java location, $JAVA_HOME check
 
-ifeq ($(wildcard $(_DESKTOP_JAVA_INCLUDE_DIRS)),)
-LATEST_JDK                  := $(shell ls -dtr $(_LINUX_JAVA_FALLBACK_DIRS) | $(_VERSION_SORT))
+ifeq ($(wildcard $(_LINUX_JAVA_FALLBACK_ROOT)),)
+LATEST_JDK                  := $(call FindJdkDirectory,$(_LINUX_JAVA_FALLBACK_ROOT)  | tr -d '[[:space:]]')
 _DESKTOP_JAVA_INCLUDE_DIRS  = $(LATEST_JDK)/$(_LINUX_JAVA_JNI_INCLUDE_DIR)
 _LINUX_JAVA_ROOT            = $(LATEST_JDK)
 endif # No $JAVA_HOME, find the latest version

build-tools/scripts/jdk.targets

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <UsingTask  TaskName="Java.Interop.BootstrapTasks.JdkDirectoryFinder"   AssemblyFile="$(MSBuildThisFileDirectory)..\..\bin\Build$(Configuration)\Java.Interop.BootstrapTasks.dll" />
+  <Target Name="GetPreferredJdkRoot">
+    <JdkDirectoryFinder
+        JdksRoot="$(JdksRoot)"
+        MaximumJdkVersion="$(MaximumJdkVersion)">
+      <Output TaskParameter="PreferredJdkRoot" PropertyName="_JdkRoot"/>
+    </JdkDirectoryFinder>
+    <Message
+        Text="$(_JdkRoot)"
+        Importance="High"
+    />
+  </Target>
+</Project>

src/Java.Interop.BootstrapTasks.tpnitems

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup Condition=" '$(TpnIncludeExternalDependencies)' == 'True' ">
+    <!-- src/Java.Interop.BootstrapTasks/Cadenza/NaturalStringComparer.cs -->
+    <ThirdPartyNotice
+        Condition=" '$(TpnIncludeBuildDependencies)' == 'True' "
+        Include="cadenza/cadenza">
+      <LicenseText>
+        Copyright (c) 2007, 2008 Novell, Inc.
+        and the individuals listed on the ChangeLog entries.
+
+        Permission is hereby granted, free of charge, to any person obtaining
+        a copy of this software and associated documentation files (the
+        "Software"), to deal in the Software without restriction, including
+        without limitation the rights to use, copy, modify, merge, publish,
+        distribute, sublicense, and/or sell copies of the Software, and to
+        permit persons to whom the Software is furnished to do so, subject to
+        the following conditions:
+
+        The above copyright notice and this permission notice shall be
+        included in all copies or substantial portions of the Software.
+
+        THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+        EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+        MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+        NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+        LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+        OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+        WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+      </LicenseText>
+      <SourceUrl>https://github.com/cadenza/cadenza/</SourceUrl>
+    </ThirdPartyNotice>
+  </ItemGroup>
+</Project>

src/Java.Interop.BootstrapTasks/Cadenza/NaturalStringComparer.cs

@@ -0,0 +1,76 @@
+//
+// NaturalStringComparer.cs
+//
+// Authors:
+//	 Jonathan Pryor <[email protected]>
+//
+// Copyright (C) 2008 Novell, Inc (http://www.novell.com)
+//
+// Thanks to wilco` on ##[email protected].
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+// 
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
+
+namespace Cadenza {
+
+	// https://github.com/cadenza/cadenza/blob/master/src/Cadenza/Cadenza/NaturalStringComparer.cs
+	sealed class NaturalStringComparer : IComparer<string>, System.Collections.IComparer
+	{
+
+		static readonly NaturalStringComparer _default = new NaturalStringComparer ();
+
+		private NaturalStringComparer ()
+		{
+		}
+
+		public static NaturalStringComparer Default {
+			get {
+				return _default;
+			}
+		}
+
+		public int Compare (string x, string y)
+		{
+			string left  = x ?? "";
+			string right = y ?? "";
+			return Regex.Replace (left, @"([\d]+)|([^\d]+)",
+					m => (m.Value.Length > 0 && char.IsDigit(m.Value[0]))
+						? m.Value.PadLeft (System.Math.Max(left.Length, right.Length))
+						: m.Value
+			).CompareTo (Regex.Replace(right, @"([\d]+)|([^\d]+)",
+					m => (m.Value.Length > 0 && char.IsDigit(m.Value[0]))
+						? m.Value.PadLeft (System.Math.Max(left.Length, right.Length))
+						: m.Value));
+		}
+
+		int System.Collections.IComparer.Compare (object x, object y)
+		{
+			return Compare (
+					x != null ? x.ToString () : "",
+					y != null ? y.ToString () : "");
+		}
+	}
+}
+

src/Java.Interop.BootstrapTasks/Java.Interop.BootstrapTasks.csproj

@@ -37,11 +37,13 @@
     <Reference Include="Microsoft.Build.Utilities.v4.0" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Cadenza\NaturalStringComparer.cs" />
     <Compile Include="Java.Interop.BootstrapTasks\DownloadUri.cs" />
+    <Compile Include="Java.Interop.BootstrapTasks\JdkDirectoryFinder.cs" />
     <Compile Include="Java.Interop.BootstrapTasks\JdkInfo.cs" />
     <Compile Include="Java.Interop.BootstrapTasks\RegistryEx.cs" />
-    <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Java.Interop.BootstrapTasks\SetEnvironmentVariable.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
 </Project>

src/Java.Interop.BootstrapTasks/Java.Interop.BootstrapTasks/JdkDirectoryFinder.cs

@@ -0,0 +1,62 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.RegularExpressions;
+
+using Cadenza;
+
+using Microsoft.Build.Utilities;
+using Microsoft.Build.Framework;
+
+namespace Java.Interop.BootstrapTasks {
+
+	public class JdkDirectoryFinder : Task {
+
+		[Required]
+		public  string  JdksRoot              { get; set; }
+
+		public  string  MaximumJdkVersion     { get; set; }
+
+		[Output]
+		public  string  PreferredJdkRoot      { get; set; }
+
+		static  Regex   VersionExtractor  = new Regex (@"(?<version>[\d]+(\.\d+)+)", RegexOptions.Compiled);
+
+		public override bool Execute ()
+		{
+			var version = GetMaxJdkVersion ();
+			var dirs    = new List<string>();
+			foreach (var d in Directory.EnumerateDirectories (JdksRoot)) {
+				var n = Path.GetFileName (d);
+				var m = version == null ? null : VersionExtractor.Match (n);
+				Version v;
+
+				if (version == null || !m.Success || !Version.TryParse (m.Groups ["version"].Value, out v)) {
+					dirs.Add (d);
+					continue;
+				}
+				if (v <= version) {
+					dirs.Add (d);
+				}
+			}
+			dirs.Sort (NaturalStringComparer.Default);
+
+			if (dirs.Count > 0) {
+				PreferredJdkRoot = dirs [dirs.Count-1];
+			}
+
+			return true;
+		}
+
+		Version GetMaxJdkVersion ()
+		{
+			if (string.IsNullOrEmpty (MaximumJdkVersion))
+				return null;
+			if (!MaximumJdkVersion.Contains (".")) {
+				MaximumJdkVersion += ".0";
+			}
+			return new Version (MaximumJdkVersion);
+		}
+	}
+}