Locate docker and docker-compose using the path variable.

This searches through the path variable's directories for the docker
commands, instead of looking in predetermined OS-specific locations or
requiring new environmental variables to be set.

This also renames DockerCommandLocations to DockerCommandLocator, which better
reflects what it is.

.baseline/findbugs/excludeFilter.xml

@@ -9,7 +9,7 @@
     <!-- Ignore the following bug patterns in test code -->
     <!-- (i.e., classes ending in 'Test' or 'Tests', and inner classes of same) -->
     <Match>
-        <Class name="~.*\.*Tests?(\$.*)?" />
+        <Class name="~.*\.*(Test|Tests|Should)?(\$.*)?" />
         <Or>
             <Bug pattern="NP_NONNULL_FIELD_NOT_INITIALIZED_IN_CONSTRUCTOR"/> <!-- common in tests to have non-final variables instantiated in @Before methods, which FindBugs can't detect -->
             <Bug pattern="NP_NULL_ON_SOME_PATH_FROM_RETURN_VALUE"/> <!-- if a null is dereferenced, test will fail anyway. Plus assertNotNull() is often a bad pattern. -->

docker-compose-rule-core/src/main/java/com/palantir/docker/compose/execution/DockerCommandLocator.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2016 Palantir Technologies, Inc. All rights reserved.
+ *
+ * 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.palantir.docker.compose.execution;
+
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Map;
+import java.util.regex.Pattern;
+
+import org.apache.commons.lang3.SystemUtils;
+
+public class DockerCommandLocator
+{
+    private static final Pattern PATH_SPLITTER = Pattern.compile(File.pathSeparator);
+
+    private final String command;
+
+    public DockerCommandLocator(String command) {
+        this.command = command;
+    }
+
+    public String getLocation() {
+        // Get path variable, ignoring the case of its name
+        String path = getEnv().entrySet().stream()
+                .filter(e -> e.getKey().equalsIgnoreCase("path"))
+                .findFirst()
+                .map(Map.Entry::getValue)
+                .orElseThrow(() -> new IllegalStateException("Could not find path variable in env"));
+
+        // The filename is the same as the command, except on Windows where it ends with ".exe"
+        String filename = isWindows() ? command + ".exe" : command;
+
+        // Look through the directories in path for the given command which must exist and be executable
+        return PATH_SPLITTER.splitAsStream(path)
+                .map(p -> Paths.get(p, filename))
+                .filter(Files::exists)
+                .findFirst()
+                .map(Path::toString)
+                .orElseThrow(() -> new IllegalStateException("Could not find " + command + " in path"));
+    }
+
+    protected Map<String, String> getEnv() {
+        return System.getenv();
+    }
+
+    protected boolean isWindows() {
+        return SystemUtils.IS_OS_WINDOWS;
+    }
+
+    @Override
+    public String toString() {
+        return "DockerCommandLocator{command=" + command + "}";
+    }
+}

docker-compose-rule-core/src/main/java/com/palantir/docker/compose/execution/DockerComposeExecutable.java

@@ -29,19 +29,9 @@
 public abstract class DockerComposeExecutable implements Executable {
     private static final Logger log = LoggerFactory.getLogger(DockerComposeExecutable.class);
 
-    private static final DockerCommandLocations DOCKER_COMPOSE_LOCATIONS = new DockerCommandLocations(
-            System.getenv("DOCKER_COMPOSE_LOCATION"),
-            "/usr/local/bin/docker-compose",
-            "/usr/bin/docker-compose"
-    );
-
     private static String defaultDockerComposePath() {
-        String pathToUse = DOCKER_COMPOSE_LOCATIONS.preferredLocation()
-                .orElseThrow(() -> new IllegalStateException(
-                        "Could not find docker-compose, looked in: " + DOCKER_COMPOSE_LOCATIONS));
-
+        String pathToUse = new DockerCommandLocator("docker-compose").getLocation();
         log.debug("Using docker-compose found at " + pathToUse);
-
         return pathToUse;
     }
 

docker-compose-rule-core/src/main/java/com/palantir/docker/compose/execution/DockerExecutable.java

@@ -26,12 +26,6 @@
 public abstract class DockerExecutable implements Executable {
     private static final Logger log = LoggerFactory.getLogger(DockerExecutable.class);
 
-    private static final DockerCommandLocations DOCKER_LOCATIONS = new DockerCommandLocations(
-            System.getenv("DOCKER_LOCATION"),
-            "/usr/local/bin/docker",
-            "/usr/bin/docker"
-    );
-
     @Value.Parameter protected abstract DockerConfiguration dockerConfiguration();
 
     @Override
@@ -41,12 +35,8 @@ public final String commandName() {
 
     @Value.Derived
     protected String dockerPath() {
-        String pathToUse = DOCKER_LOCATIONS.preferredLocation()
-                .orElseThrow(() -> new IllegalStateException(
-                        "Could not find docker, looked in: " + DOCKER_LOCATIONS));
-
+        String pathToUse = new DockerCommandLocator("docker").getLocation();
         log.debug("Using docker found at " + pathToUse);
-
         return pathToUse;
     }
 

docker-compose-rule-core/src/test/java/com/palantir/docker/compose/execution/DockerCommandLocatorShould.java

@@ -0,0 +1,115 @@
+/*
+ * Copyright 2016 Palantir Technologies, Inc. All rights reserved.
+ *
+ * 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.palantir.docker.compose.execution;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.spy;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.junit.rules.TemporaryFolder;
+
+public class DockerCommandLocatorShould {
+    private static final String command = "command";
+    private static final String windowsCommand = command + ".exe";
+
+    @Rule public TemporaryFolder folder = new TemporaryFolder();
+
+    @Rule public ExpectedException exception = ExpectedException.none();
+
+    private final DockerCommandLocator locator = spy(new DockerCommandLocator(command));
+
+    private final Map<String, String> env = new HashMap<>();
+
+    private Path emptyFolder;
+
+    private Path firstFolder;
+
+    private Path secondFolder;
+
+    private String commandFile;
+
+    private String windowsCommandFile;
+
+    private String pathString;
+
+    @Before
+    public void setup() throws IOException {
+        emptyFolder = folder.newFolder("empty").toPath();
+        firstFolder = folder.newFolder("first").toPath();
+        secondFolder = folder.newFolder("second").toPath();
+
+        commandFile = Files.createFile(firstFolder.resolve(command)).toString();
+        windowsCommandFile = Files.createFile(firstFolder.resolve(windowsCommand)).toString();
+        Files.createFile(secondFolder.resolve(command));
+        Files.createFile(secondFolder.resolve(windowsCommand));
+
+        pathString = Stream.of(emptyFolder, firstFolder, secondFolder)
+                .map(Path::toString)
+                .collect(Collectors.joining(File.pathSeparator));
+
+        doReturn(env).when(locator).getEnv();
+    }
+
+    @Test public void
+    provide_the_first_command_location() {
+        env.put("path", pathString);
+        doReturn(false).when(locator).isWindows();
+        assertThat(locator.getLocation(), is(commandFile));
+    }
+
+    @Test public void
+    provide_the_first_command_location_using_capitalised_path() {
+        env.put("PATH", pathString);
+        doReturn(false).when(locator).isWindows();
+        assertThat(locator.getLocation(), is(commandFile));
+    }
+
+    @Test public void
+    provide_the_first_command_location_on_windows() {
+        env.put("path", pathString);
+        doReturn(true).when(locator).isWindows();
+        assertThat(locator.getLocation(), is(windowsCommandFile));
+    }
+
+    @Test public void
+    fail_when_no_paths_contain_command() {
+        env.put("path", emptyFolder.toString());
+        exception.expect(IllegalStateException.class);
+        exception.expectMessage("Could not find " + command + " in path");
+        locator.getLocation();
+    }
+
+    @Test public void
+    fail_when_no_path_variable_is_set() {
+        exception.expect(IllegalStateException.class);
+        exception.expectMessage("Could not find path variable in env");
+        locator.getLocation();
+    }
+}