Improve script quoting

src/main/java/io/github/ascopes/protobufmavenplugin/dependency/JvmPluginResolver.java

@@ -20,6 +20,7 @@
 import io.github.ascopes.protobufmavenplugin.system.Digests;
 import io.github.ascopes.protobufmavenplugin.system.FileUtils;
 import io.github.ascopes.protobufmavenplugin.system.HostSystem;
+import io.github.ascopes.protobufmavenplugin.system.Shlex;
 import java.io.IOException;
 import java.nio.charset.Charset;
 import java.nio.file.Files;
@@ -151,70 +152,27 @@ private Path writeWindowsBatchScript(
   ) throws IOException {
     var fullScriptPath = resolvePluginScriptPath().resolve(scriptNamePrefix + ".bat");
 
-    var script = new StringBuilder()
-        .append("@echo off\r\n");
-    for (var arg : argLine) {
-      quoteBatchArg(script, arg);
-      script.append(' ');
-    }
-    script.append("\r\n");
+    var script = "@echo off\r\n"
+        + Shlex.quoteBatchArgs(argLine)
+        + "\r\n";
 
     Files.writeString(fullScriptPath, script, Charset.defaultCharset());
     return fullScriptPath;
   }
 
-  private void quoteBatchArg(StringBuilder sb, String arg) {
-    for (var i = 0; i < arg.length(); ++i) {
-      var c = arg.charAt(i);
-      switch (c) {
-        case '\\':
-        case '"':
-        case '\'':
-        case ' ':
-        case '\r':
-        case '\t':
-        case '^':
-        case '&':
-        case '<':
-        case '>':
-        case '|':
-          sb.append('^');
-      }
-
-      sb.append(c);
-    }
-  }
-
   private Path writeShellScript(
       String scriptNamePrefix,
       List<String> argLine
   ) throws IOException {
     var fullScriptPath = resolvePluginScriptPath().resolve(scriptNamePrefix + ".sh");
 
-    var script = new StringBuilder()
-        .append("#!/usr/bin/env sh\n")
-        .append("set -eux\n");
-    for (var arg : argLine) {
-      quoteShellArg(script, arg);
-      script.append(' ');
-    }
-    script.append('\n');
+    var script = "#!/usr/bin/env sh\n"
+        + "set -eu\n"
+        + Shlex.quoteShellArgs(argLine)
+        + "\n";
 
     Files.writeString(fullScriptPath, script, Charset.defaultCharset());
     FileUtils.makeExecutable(fullScriptPath);
     return fullScriptPath;
   }
-
-  private void quoteShellArg(StringBuilder sb, String arg) {
-    sb.append('\'');
-    for (var i = 0; i < arg.length(); ++i) {
-      var c = arg.charAt(i);
-      if (c == '\'') {
-        sb.append("'\"'\"'");
-      } else {
-        sb.append(c);
-      }
-    }
-    sb.append('\'');
-  }
 }

src/main/java/io/github/ascopes/protobufmavenplugin/execute/CommandLineExecutor.java

@@ -15,6 +15,7 @@
  */
 package io.github.ascopes.protobufmavenplugin.execute;
 
+import io.github.ascopes.protobufmavenplugin.system.Shlex;
 import java.io.IOException;
 import java.io.InterruptedIOException;
 import java.util.List;
@@ -39,7 +40,7 @@ public CommandLineExecutor() {
   }
 
   public boolean execute(List<String> args) throws IOException {
-    log.info("Calling protoc with the following command line: {}", args);
+    log.info("Calling protoc with the following command line: {}", Shlex.quoteShellArgs(args));
 
     var procBuilder = new ProcessBuilder(args);
     procBuilder.environment().putAll(System.getenv());

src/main/java/io/github/ascopes/protobufmavenplugin/system/Shlex.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2023 - 2024, Ashley Scopes.
+ *
+ * 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 io.github.ascopes.protobufmavenplugin.system;
+
+import java.util.function.BiConsumer;
+
+/**
+ * Shell/batch file quoting.
+ *
+ * <p>Losely based on Python's {@code shlex} module.
+ *
+ * @author Ashley Scopes
+ */
+public final class Shlex {
+
+  private Shlex() {
+    // Static-only class
+  }
+
+  public static String quoteShellArgs(Iterable<String> args) {
+    return quote(args, Shlex::quoteShellArg);
+  }
+
+  public static String quoteBatchArgs(Iterable<String> args) {
+    return quote(args, Shlex::quoteBatchArg);
+  }
+
+  private static String quote(Iterable<String> args, BiConsumer<StringBuilder, String> quoter) {
+    var iter = args.iterator();
+    var sb = new StringBuilder();
+    quoter.accept(sb, iter.next());
+
+    while (iter.hasNext()) {
+      sb.append(' ');
+      quoter.accept(sb, iter.next());
+    }
+
+    return sb.toString();
+  }
+
+  private static void quoteShellArg(StringBuilder sb, String arg) {
+    if (isSafe(arg)) {
+      sb.append(arg);
+      return;
+    }
+
+    sb.append('\'');
+    for (var i = 0; i < arg.length(); ++i) {
+      var c = arg.charAt(i);
+      if (c == '\'') {
+        sb.append("'\"'\"'");
+      } else {
+        sb.append(c);
+      }
+    }
+    sb.append('\'');
+  }
+
+  private static void quoteBatchArg(StringBuilder sb, String arg) {
+    if (isSafe(arg)) {
+      sb.append(arg);
+      return;
+    }
+
+    for (var i = 0; i < arg.length(); ++i) {
+      var c = arg.charAt(i);
+      switch (c) {
+        case '\\':
+        case '"':
+        case '\'':
+        case ' ':
+        case '\r':
+        case '\t':
+        case '^':
+        case '&':
+        case '<':
+        case '>':
+        case '|':
+          sb.append('^');
+      }
+
+      sb.append(c);
+    }
+  }
+
+  private static boolean isSafe(String arg) {
+    for (var i = 0; i < arg.length(); ++i) {
+      var c = arg.charAt(i);
+      var safe = 'A' <= c && c <= 'Z'
+          || 'a' <= c && c <= 'z'
+          || '0' <= c && c <= '9'
+          || c == '-'
+          || c == '/'
+          || c == '_'
+          || c == '.'
+          || c == '=';
+
+      if (!safe) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+}