/*
 * Copyright 2013-present Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License. You may obtain
 * a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package com.facebook.buck.rules.coercer;

import com.facebook.buck.rules.BuildRuleFactoryParams;
import com.facebook.buck.rules.BuildRuleResolver;
import com.facebook.buck.util.BuckConstant;
import com.facebook.buck.util.ProjectFilesystem;

import java.nio.file.Path;
import java.nio.file.Paths;

public class PathTypeCoercer extends LeafTypeCoercer<Path> {

  @Override
  public Class<Path> getOutputClass() {
    return Path.class;
  }

  @Override
  public Path coerce(
      BuildRuleResolver buildRuleResolver,
      ProjectFilesystem filesystem,
      Path pathRelativeToProjectRoot,
      Object object) throws CoerceFailedException {
    if (object instanceof String) {
      String path = (String) object;
      if (path.startsWith(BuildRuleFactoryParams.GENFILE_PREFIX)) {
        path = path.substring(BuildRuleFactoryParams.GENFILE_PREFIX.length());

        // A genfile is created during the build, so it's legit that it might not exist.
        return Paths.get(BuckConstant.GEN_DIR)
            .resolve(pathRelativeToProjectRoot)
            .resolve(path)
            .normalize();
      } else {
        Path normalizedPath = pathRelativeToProjectRoot.resolve(path).normalize();
        // Verify that the path exists
        filesystem.getPathForRelativeExistingPath(normalizedPath);

        return normalizedPath;
      }
    } else {
      throw CoerceFailedException.simple(pathRelativeToProjectRoot, object, getOutputClass());
    }
  }
}

@@ -1711,24 +1711,40 @@
    %7D else %7B%0A
+        try %7B%0A  
         Path
@@ -1822,16 +1822,18 @@
         
+ 
+ 
 // Verif
@@ -1855,16 +1855,18 @@
  exists%0A
+  
         
@@ -1929,24 +1929,26 @@
 );%0A%0A        
+  
 return norma
@@ -1958,16 +1958,124 @@
 edPath;%0A
+        %7D catch (RuntimeException e) %7B%0A          throw new CoerceFailedException(e.getMessage());%0A        %7D%0A
       %7D%0A

Convert a RuntimeException to a CoerceException in the PathTypeCoercer