[SQLLINE-394] Make script engine configurable via new scriptEngine property

This compensates for the fact that Nashorn is not available
on JDK 15 and higher.

Close #422

Author: snuyanzin

src/docbkx/manual.xml

@@ -3507,6 +3507,13 @@ java.sql.SQLException: ORA-00942: table or view does not exist
           Defaults to 0, which is interpreted as fetching all rows.
         </para>
       </sect1>
+      <sect1 id="setting_scriptengine">
+        <title>scriptengine</title>
+        <para>
+          A script engine to use to evaluate scripts for
+          instance from promptScript. Defaults to nashorn.
+        </para>
+      </sect1>
       <sect1 id="setting_showcompletiondesc">
         <title>showcompletiondesc</title>
         <para>

src/main/java/sqlline/Application.java

@@ -19,13 +19,16 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Properties;
 import java.util.ServiceLoader;
 import java.util.Set;
 import java.util.TreeSet;
+import javax.script.ScriptEngineFactory;
+import javax.script.ScriptEngineManager;
 
 import org.jline.builtins.Completers.FileNameCompleter;
 import org.jline.reader.Completer;
@@ -373,6 +376,38 @@ public String getDefaultInteractiveMode() {
   public Map<String, TableOutputFormatStyle> getName2TableOutputFormatStyle() {
     return BuiltInTableOutputFormatStyles.BY_NAME;
   }
+
+  /**
+   * Override this method to modify available script engine names.
+   *
+   * <p>If method is not overridden, current set of engine names will
+   * contain first non intersected values (ordered by abc).
+   *
+   * @return Set of available script engine names
+   */
+  public Set<String> getAvailableScriptEngineNames() {
+    final Set<String> result = new HashSet<>();
+    final Map<String, Set<String>> fName2Aliases = new HashMap<>();
+    final List<ScriptEngineFactory> factories =
+        new ScriptEngineManager().getEngineFactories();
+    for (ScriptEngineFactory factory: factories) {
+      fName2Aliases.put(factory.getEngineName(),
+          new HashSet<>(factory.getNames()));
+    }
+    for (Map.Entry<String, Set<String>> fEntry: fName2Aliases.entrySet()) {
+      Set<String> aliases = new TreeSet<>(fEntry.getValue());
+      for (Map.Entry<String, Set<String>> fEntry2: fName2Aliases.entrySet()) {
+        if (fEntry.getKey().equals(fEntry2.getKey())) {
+          continue;
+        }
+        aliases.removeAll(fEntry2.getValue());
+      }
+      if (!aliases.isEmpty()) {
+        result.add(aliases.iterator().next());
+      }
+    }
+    return result;
+  }
 }
 
 // End Application.java

src/main/java/sqlline/BuiltInProperty.java

@@ -87,6 +87,8 @@ public enum BuiltInProperty implements SqlLineProperty {
   RIGHT_PROMPT("rightPrompt", Type.STRING, ""),
   ROW_LIMIT("rowLimit", Type.INTEGER, 0),
   SHOW_ELAPSED_TIME("showElapsedTime", Type.BOOLEAN, true),
+  SCRIPT_ENGINE("scriptEngine", Type.STRING, "nashorn", true, false,
+      new Application().getAvailableScriptEngineNames()),
   SHOW_COMPLETION_DESCR("showCompletionDesc", Type.BOOLEAN, true),
   SHOW_HEADER("showHeader", Type.BOOLEAN, true),
   SHOW_LINE_NUMBERS("showLineNumbers", Type.BOOLEAN, false),

src/main/java/sqlline/PromptHandler.java

@@ -61,11 +61,26 @@ public class PromptHandler {
 
   protected final SqlLine sqlLine;
 
-  static final Supplier<ScriptEngine> SCRIPT_ENGINE_SUPPLIER =
-      new MemoizingSupplier<>(() -> {
-        final ScriptEngineManager engineManager = new ScriptEngineManager();
-        return engineManager.getEngineByName("nashorn");
-      });
+  final Supplier<ScriptEngine> scriptEngineSupplier =
+      getEngineSupplier();
+
+  MemoizingSupplier<ScriptEngine> getEngineSupplier() {
+    return new MemoizingSupplier<>(() -> {
+      final ScriptEngineManager engineManager = new ScriptEngineManager();
+      String engineName = sqlLine.getOpts().get(BuiltInProperty.SCRIPT_ENGINE);
+      ScriptEngine scriptEngine = engineManager.getEngineByName(engineName);
+      if (scriptEngine == null) {
+        if (engineManager.getEngineFactories().isEmpty()) {
+          sqlLine.error(sqlLine.loc("not-supported-script-engine-no-available",
+              engineName));
+        } else {
+          sqlLine.error(sqlLine.loc("not-supported-script-engine",
+              engineName, BuiltInProperty.SCRIPT_ENGINE.getAvailableValues()));
+        }
+      }
+      return scriptEngine;
+    });
+  }
 
   public PromptHandler(SqlLine sqlLine) {
     this.sqlLine = sqlLine;
@@ -112,16 +127,20 @@ public AttributedString getPrompt() {
   private String getPromptFromScript(SqlLine sqlLine,
       String promptScript) {
     try {
-      final ScriptEngine engine = SCRIPT_ENGINE_SUPPLIER.get();
-      final Bindings bindings = new SimpleBindings();
-      final ConnectionMetadata meta = sqlLine.getConnectionMetadata();
-      bindings.put("connectionIndex", meta.getIndex());
-      bindings.put("databaseProductName", meta.getDatabaseProductName());
-      bindings.put("userName", meta.getUserName());
-      bindings.put("url", meta.getUrl());
-      bindings.put("currentSchema", meta.getCurrentSchema());
-      final Object o = engine.eval(promptScript, bindings);
-      return String.valueOf(o);
+      final ScriptEngine engine = scriptEngineSupplier.get();
+      if (engine == null) {
+        return ">";
+      } else {
+        final Bindings bindings = new SimpleBindings();
+        final ConnectionMetadata meta = sqlLine.getConnectionMetadata();
+        bindings.put("connectionIndex", meta.getIndex());
+        bindings.put("databaseProductName", meta.getDatabaseProductName());
+        bindings.put("userName", meta.getUserName());
+        bindings.put("url", meta.getUrl());
+        bindings.put("currentSchema", meta.getCurrentSchema());
+        final Object o = engine.eval(promptScript, bindings);
+        return String.valueOf(o);
+      }
     } catch (ScriptException e) {
       e.printStackTrace();
       return ">";

src/main/java/sqlline/SqlLineOpts.java

@@ -23,6 +23,8 @@
 import java.util.regex.Pattern;
 import java.util.regex.PatternSyntaxException;
 import java.util.stream.Collectors;
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineManager;
 
 import org.jline.builtins.Completers;
 import org.jline.keymap.KeyMap;
@@ -75,6 +77,7 @@
 import static sqlline.BuiltInProperty.PROPERTIES_FILE;
 import static sqlline.BuiltInProperty.RIGHT_PROMPT;
 import static sqlline.BuiltInProperty.ROW_LIMIT;
+import static sqlline.BuiltInProperty.SCRIPT_ENGINE;
 import static sqlline.BuiltInProperty.SHOW_COMPLETION_DESCR;
 import static sqlline.BuiltInProperty.SHOW_ELAPSED_TIME;
 import static sqlline.BuiltInProperty.SHOW_HEADER;
@@ -130,6 +133,7 @@ public class SqlLineOpts implements Completer {
               put(NUMBER_FORMAT, SqlLineOpts.this::setNumberFormat);
               put(OUTPUT_FORMAT, SqlLineOpts.this::setOutputFormat);
               put(PROPERTIES_FILE, SqlLineOpts.this::setPropertiesFile);
+              put(SCRIPT_ENGINE, SqlLineOpts.this::setScriptEngine);
               put(SHOW_COMPLETION_DESCR,
                   SqlLineOpts.this::setShowCompletionDesc);
               put(TABLE_STYLE, SqlLineOpts.this::setTableStyle);
@@ -523,7 +527,8 @@ public void set(SqlLineProperty key, Object value) {
           ? (String) value : String.valueOf(value);
       valueToSet = DEFAULT.equalsIgnoreCase(strValue)
           ? key.defaultValue() : value;
-      if (!key.getAvailableValues().isEmpty()
+      if (!DEFAULT.equalsIgnoreCase(strValue)
+          && !key.getAvailableValues().isEmpty()
           && !key.getAvailableValues().contains(valueToSet.toString())) {
         sqlLine.error(
             sqlLine.loc("unknown-value",
@@ -1083,6 +1088,24 @@ public Pattern getCompiledConfirmPattern() {
   public String getHistoryFlags() {
     return get(HISTORY_FLAGS);
   }
+
+  public String getScriptEngine() {
+    return get(SCRIPT_ENGINE);
+  }
+
+  public void setScriptEngine(String engineName) {
+    if (DEFAULT.equalsIgnoreCase(engineName)) {
+      set(SCRIPT_ENGINE, SCRIPT_ENGINE.defaultValue());
+      return;
+    }
+    final ScriptEngineManager engineManager = new ScriptEngineManager();
+    ScriptEngine scriptEngine = engineManager.getEngineByName(engineName);
+    if (scriptEngine == null && engineManager.getEngineFactories().isEmpty()) {
+      sqlLine.error(sqlLine.loc("not-supported-script-engine-no-available",
+          engineName));
+    }
+    set(SCRIPT_ENGINE, engineName);
+  }
 }
 
 // End SqlLineOpts.java

src/main/resources/sqlline/SqlLine.properties

@@ -37,6 +37,8 @@ column: Column
 new-size-after-resize: New size: height = {0}, width = {1}
 empty-value-not-supported: Empty value for type {0} not supported
 no-file: File {0} does not exist or is a directory
+not-supported-script-engine: Not found script engine "{0}", available values: {1}
+not-supported-script-engine-no-available: Not found script engine "{0}", no available script engines
 
 jdbc-level: JDBC level
 compliant: Compliant
@@ -151,6 +153,7 @@ variables:\
 \nrightPrompt     pattern    Format right prompt\
 \nrowLimit        integer    Maximum number of rows returned from a query; zero\
 \n                           means no limit\
+\nscriptEngine    String     Script engine name\
 \nshowCompletionDesc true/false Display help for completions\
 \nshowElapsedTime true/false Display execution time when verbose\
 \nshowHeader      true/false Show column names in query results\
@@ -340,6 +343,7 @@ cmd-usage: Usage: java sqlline.SqlLine \n \
 \  --autoCommit=[true/false]       enable/disable automatic transaction commit\n \
 \  --readOnly=[true/false]         enable/disable readonly connection\n \
 \  --verbose=[true/false]          show verbose error messages and debug info\n \
+\  --scriptEngine=[string]         script engine name\n \
 \  --showCompletionDesc=[true/false] display help for completions\n \
 \  --showLineNumbers=[true/false]  show line numbers while multiline queries\n \
 \  --showTime=[true/false]         display execution time when verbose\n \

src/main/resources/sqlline/manual.txt

@@ -104,6 +104,8 @@ schemas
 schemas — List all the schemas in the database
 script
 script — Save executed commands to a file
+scriptengine
+scriptengine - script engine name
 set
 set — Set a preference
 showconfconnections
@@ -258,6 +260,8 @@ scan
 scan — Scan class path for JDBC drivers
 script
 script — Save executed commands to a file
+scriptengine
+scriptengine - script engine name
 set
 set — Set a preference
 showconfconnections
@@ -502,6 +506,8 @@ scan
 scan — Scan class path for JDBC drivers
 script
 script — Save executed commands to a file
+scriptengine
+scriptengine - script engine name
 set
 set — Set a preference
 showconfconnections
@@ -1223,6 +1229,7 @@ propertiesFile  path       File from which SQLLine reads properties on
 rightPrompt     pattern    Format right prompt
 rowLimit        integer    Maximum number of rows returned from a query; zero
                            means no limit
+scriptEngine    string     Script engine name
 showCompletionDesc true/false Display help for completions
 showElapsedTime true/false Display execution time when verbose
 showHeader      true/false Show column names in query results
@@ -2411,6 +2418,10 @@ rowlimit
 
 The maximum number of rows to fetch per query. Defaults to 0, which is interpreted as fetching all rows.
 
+scriptengine
+
+A script engine to use to evaluate scripts for instance from promptScript. Defaults to nashorn.
+
 showheader
 
 If true, display the names of the columns when displaying results. Defaults to true.

src/test/java/sqlline/PromptTest.java

@@ -15,6 +15,7 @@
 import java.text.SimpleDateFormat;
 import java.util.Date;
 import java.util.Locale;
+import javax.script.ScriptEngineManager;
 
 import org.jline.utils.AttributedString;
 import org.jline.utils.AttributedStringBuilder;
@@ -221,8 +222,9 @@ public void testPromptWithSchema() {
    * The `promptscript` property is broken on JDK 15 and higher</a>. */
   @Test
   public void testPromptScript() {
-    Assumptions.assumeTrue(getJavaMajorVersion() < 15,
-        "promptscript fails on JDK 15 and higher; "
+    Assumptions.assumeTrue(
+        !new ScriptEngineManager().getEngineFactories().isEmpty(),
+        "promptscript fails if there is no script engines; "
             + "see ");
 
     sqlLine.getOpts().set(BuiltInProperty.PROMPT_SCRIPT, "'hel' + 'lo'");