Extract wsl tool to get info from registry

* WSLDistributionWithRoot wraps WSLDistribution and uses registry to get basepath
* WSL#getWindowsPath capitalizes disk letter
* WSLDistributionWithRoot applies "toCanonicalPath" to its argument

platform/platform-impl/src/com/intellij/execution/wsl/WSLDistribution.java

@@ -29,6 +29,7 @@ import java.util.stream.Collectors;
  * Represents a single linux distribution in WSL, installed after <a href="https://blogs.msdn.microsoft.com/commandline/2017/10/11/whats-new-in-wsl-in-windows-10-fall-creators-update/">Fall Creators Update</a>
  *
  * @see WSLUtil
+ * @see WSLDistributionWithRoot
  */
 public class WSLDistribution {
   static final String WSL_MNT_ROOT = "/mnt/";

platform/platform-impl/src/com/intellij/execution/wsl/WSLDistributionWithRoot.java

@@ -0,0 +1,79 @@
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.execution.wsl;
+
+import com.intellij.openapi.diagnostic.Logger;
+import com.intellij.openapi.util.AtomicNotNullLazyValue;
+import com.intellij.openapi.util.io.FileUtil;
+import com.intellij.openapi.util.io.WindowsRegistryUtil;
+import com.intellij.util.containers.ContainerUtil;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Wraps {@link WSLDistribution} and fetches data from registry to find base path of distro on Windows
+ */
+public class WSLDistributionWithRoot extends WSLDistribution {
+  private final static Logger LOG = Logger.getInstance(WSLDistributionWithRoot.class);
+  private static final AtomicNotNullLazyValue<Map<String, String>> DISTRIBUTION_TO_ROOTFS =
+    AtomicNotNullLazyValue.createValue(() -> {
+      final Map<String, String> result = ContainerUtil.newHashMap();
+
+      final String lxss = "HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Lxss";
+      final List<String> distributions = WindowsRegistryUtil.readRegistryBranch(lxss);
+
+      LOG.debug("Processing Lxss registry: " + distributions.size());
+      for (String distribution : distributions) {
+        final String name = WindowsRegistryUtil.readRegistryValue(lxss + "\\" + distribution, "DistributionName");
+        final String path = WindowsRegistryUtil.readRegistryValue(lxss + "\\" + distribution, "BasePath");
+        LOG.debug(name + ": " + path);
+
+        if (path != null) {
+          result.put(name, path + "\\rootfs");
+        }
+      }
+      return Collections.unmodifiableMap(result);
+    });
+  @Nullable private final String myWslRootInHost;
+
+  public WSLDistributionWithRoot(@NotNull WSLDistribution wslDistribution) {
+    super(wslDistribution);
+    String wslRootInHost = DISTRIBUTION_TO_ROOTFS.getValue().get(wslDistribution.getMsId());
+
+    if (wslRootInHost == null) {
+      LOG.warn("WSL rootfs is null");
+    }
+    else if (!FileUtil.exists(wslRootInHost)) {
+      LOG.warn("WSL rootfs doesn't exist: " + wslRootInHost);
+      wslRootInHost = null;
+    }
+    myWslRootInHost = wslRootInHost;
+  }
+
+  @Nullable
+  @Override
+  public String getWslPath(@NotNull String windowsPath) {
+    String canonicalPath = FileUtil.toCanonicalPath(windowsPath);
+    if (myWslRootInHost != null && FileUtil.isAncestor(myWslRootInHost, canonicalPath, true)) {  // this is some internal WSL path
+      return FileUtil.toSystemIndependentName(canonicalPath.substring(myWslRootInHost.length()));
+    }
+    return super.getWslPath(canonicalPath);
+  }
+
+  @Nullable
+  @Override
+  public String getWindowsPath(@NotNull String wslPath) {
+    String windowsPath = super.getWindowsPath(wslPath);
+    if (windowsPath != null) {
+      return windowsPath;
+    }
+
+    if (myWslRootInHost == null) {
+      return null;
+    }
+    return FileUtil.toSystemDependentName(myWslRootInHost + FileUtil.toCanonicalPath(wslPath));
+  }
+}

platform/platform-impl/src/com/intellij/execution/wsl/WSLUtil.java

@@ -150,6 +150,6 @@ public class WSLUtil {
     if (slashIndex < wslPath.length() && wslPath.charAt(slashIndex) != '/') {
       return null;
     }
-    return FileUtil.toSystemDependentName(wslPath.charAt(driveLetterIndex) + ":" + wslPath.substring(slashIndex));
+    return FileUtil.toSystemDependentName(Character.toUpperCase(wslPath.charAt(driveLetterIndex)) + ":" + wslPath.substring(slashIndex));
   }
 }