[ExecMojo]Add getShebang method to correctly set the command line executable name (#487)

* [ExecMojo]Add `getShebang` method to correctly set the command line executable name

- Update description of environmentScript
- Make getShebang package private
- Add shebang line into env.sh

Author: uchenily

src/it/projects/envscript/src/build/env.sh

@@ -1,2 +1,2 @@
-MY_ENV_SCRIPT_SET_A_VAR_TO=something
-export MY_ENV_SCRIPT_SET_A_VAR_TO
+#!/bin/sh
+export MY_ENV_SCRIPT_SET_A_VAR_TO=something

src/main/java/org/codehaus/mojo/exec/ExecMojo.java

@@ -20,6 +20,7 @@
  */
 
 import java.io.BufferedOutputStream;
+import java.io.BufferedReader;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.FileWriter;
@@ -277,9 +278,11 @@ public class ExecMojo extends AbstractExecMojo {
     private Map<String, String> environmentVariables = new HashMap<>();
 
     /**
-     * Environment script to be merged with <i>environmentVariables</i> This script is platform specifics, on Unix its
-     * must be Bourne shell format. Use this feature if you have a need to create environment variable dynamically such
-     * as invoking Visual Studio environment script file
+     * Environment script to be merged with <i>environmentVariables</i>. on Unix-like system if the script
+     * contains a shebang line, the executable filename is read from the shebang line; otherwise,
+     * Bourne shell format is used.
+     * Use this feature if you have a need to create environment variable dynamically such as invoking
+     * Visual Studio environment script file.
      *
      * @since 1.4.0
      */
@@ -1013,6 +1016,22 @@ private void createArgFile(String filePath, List<String> lines) throws IOExcepti
         }
     }
 
+    String getShebang(File script) {
+        if (script == null || !script.canRead()) {
+            getLog().warn("Cannot read script file " + script);
+            return null;
+        }
+        try (BufferedReader reader = Files.newBufferedReader(script.toPath())) {
+            String line = reader.readLine();
+            if (line != null && line.startsWith("#!")) {
+                return line.substring(2).trim();
+            }
+        } catch (IOException e) {
+            getLog().warn("Could not read shebang from " + script.getAbsolutePath(), e);
+        }
+        return null;
+    }
+
     protected Map<String, String> createEnvs(File envScriptFile) throws MojoExecutionException {
         Map<String, String> results = null;
 
@@ -1023,7 +1042,16 @@ protected Map<String, String> createEnvs(File envScriptFile) throws MojoExecutio
             Commandline cl = new Commandline(); // commons-exec instead?
             cl.setExecutable(tmpEnvExecFile.getAbsolutePath());
             if (!OS.isFamilyWindows()) {
-                cl.setExecutable("sh");
+                String shebang = getShebang(envScriptFile);
+                if (shebang != null && !shebang.isEmpty()) {
+                    String[] parts = shebang.split("\\s+");
+                    cl.setExecutable(parts[0]);
+                    for (int i = 1; i < parts.length; i++) {
+                        cl.createArg().setValue(parts[i]);
+                    }
+                } else {
+                    cl.setExecutable("sh");
+                }
                 cl.createArg().setFile(tmpEnvExecFile);
             }
 
@@ -1077,8 +1105,13 @@ protected File createEnvWrapperFile(File envScript) throws IOException {
         } else {
             tmpFile = Files.createTempFile("env", ".sh").toFile();
             // tmpFile.setExecutable( true );//java 6 only
+            String shebang = getShebang(envScript);
             try (PrintWriter writer = new PrintWriter(tmpFile)) {
-                writer.append("#! /bin/sh").println();
+                if (shebang != null && !shebang.isEmpty()) {
+                    writer.append("#!").append(shebang).println();
+                } else {
+                    writer.append("#!/bin/sh").println();
+                }
                 writer.append(". ").append(envScript.getCanonicalPath()).println(); // works on all unix??
                 writer.append("echo " + EnvStreamConsumer.START_PARSING_INDICATOR)
                         .println();

src/test/java/org/codehaus/mojo/exec/ExecMojoTest.java

@@ -356,4 +356,80 @@ private String getCommandLineAsString(CommandLine commandline) {
         }
         return result;
     }
+
+    public void testGetShebang() throws Exception {
+        ExecMojo execMojo = new ExecMojo();
+
+        // without shebang
+        File noShebang = Files.createTempFile("noShebang", ".sh").toFile();
+        Files.write(noShebang.toPath(), Arrays.asList("echo hello"), StandardCharsets.UTF_8);
+        assertNull(execMojo.getShebang(noShebang));
+        noShebang.delete();
+
+        // with shebang
+        File withShebang = Files.createTempFile("withShebang", ".sh").toFile();
+        Files.write(withShebang.toPath(), Arrays.asList("#!/bin/bash -x", "echo hello"), StandardCharsets.UTF_8);
+        assertEquals("/bin/bash -x", execMojo.getShebang(withShebang));
+        withShebang.delete();
+
+        // with shebang but no args
+        File withShebangNoArgs =
+                Files.createTempFile("withShebangNoArgs", ".sh").toFile();
+        Files.write(
+                withShebangNoArgs.toPath(),
+                Arrays.asList("#!/usr/bin/env python3", "print('hello')"),
+                StandardCharsets.UTF_8);
+        assertEquals("/usr/bin/env python3", execMojo.getShebang(withShebangNoArgs));
+        withShebangNoArgs.delete();
+    }
+
+    public void testCreateEnvWrapperFile() throws Exception {
+        ExecMojo execMojo = new ExecMojo();
+
+        // without shebang
+        File envScript = Files.createTempFile("envScript", ".sh").toFile();
+        Files.write(envScript.toPath(), Arrays.asList("export TEST_VAR=test_value"), StandardCharsets.UTF_8);
+        File wrapper = execMojo.createEnvWrapperFile(envScript);
+        List<String> lines = Files.readAllLines(wrapper.toPath(), StandardCharsets.UTF_8);
+
+        if (OS.isFamilyWindows()) {
+            assertEquals("@echo off", lines.get(0));
+            assertTrue(lines.get(1).startsWith("call \""));
+            assertTrue(lines.get(1).endsWith(envScript.getCanonicalPath() + "\""));
+            assertEquals("echo " + EnvStreamConsumer.START_PARSING_INDICATOR, lines.get(2));
+            assertEquals("set", lines.get(3));
+        } else {
+            assertEquals("#!/bin/sh", lines.get(0));
+            assertEquals(". " + envScript.getCanonicalPath(), lines.get(1));
+            assertEquals("echo " + EnvStreamConsumer.START_PARSING_INDICATOR, lines.get(2));
+            assertEquals("env", lines.get(3));
+        }
+        wrapper.delete();
+        envScript.delete();
+
+        // with shebang
+        File envScriptWithShebang =
+                Files.createTempFile("envScriptWithShebang", ".sh").toFile();
+        Files.write(
+                envScriptWithShebang.toPath(),
+                Arrays.asList("#!/bin/bash", "export TEST_VAR=test_value"),
+                StandardCharsets.UTF_8);
+        File wrapper2 = execMojo.createEnvWrapperFile(envScriptWithShebang);
+        List<String> lines2 = Files.readAllLines(wrapper2.toPath(), StandardCharsets.UTF_8);
+
+        if (OS.isFamilyWindows()) {
+            assertEquals("@echo off", lines2.get(0));
+            assertTrue(lines2.get(1).startsWith("call \""));
+            assertTrue(lines2.get(1).endsWith(envScriptWithShebang.getCanonicalPath() + "\""));
+            assertEquals("echo " + EnvStreamConsumer.START_PARSING_INDICATOR, lines2.get(2));
+            assertEquals("set", lines2.get(3));
+        } else {
+            assertEquals("#!/bin/bash", lines2.get(0));
+            assertEquals(". " + envScriptWithShebang.getCanonicalPath(), lines2.get(1));
+            assertEquals("echo " + EnvStreamConsumer.START_PARSING_INDICATOR, lines2.get(2));
+            assertEquals("env", lines2.get(3));
+        }
+        wrapper2.delete();
+        envScriptWithShebang.delete();
+    }
 }