Replace help syntax form with ,doc REPL command.

fusioncli/build.gradle.kts

@@ -33,7 +33,7 @@ tasks.jacocoTestCoverageVerification {
     violationRules {
         rule {
             limit {
-                minimum = "0.40".toBigDecimal()
+                minimum = "0.45".toBigDecimal()
             }
         }
     }

fusioncli/src/main/fusion/modules/fusion/private/cli/repl.fusion

@@ -7,18 +7,11 @@
 Helper forms for the REPL.
   '''
 
-  (require "/fusion/ffi/java")
+  (require
+    "/fusion/private/syntax")
 
   (provide
-    help
+    quote_syntax   // Needed by ,doc
   )
 
-  (define help
-    '''
-    (help ident ...)
-
-Prints documentation for the given bindings, if available.
-    '''
-    (java_new "dev.ionfusion.fusion._Private_HelpForm"))
-
 )

fusioncli/src/main/java/dev/ionfusion/fusioncli/repl/RepLoop.java

@@ -7,6 +7,7 @@
 
 import com.amazon.ion.IonException;
 import dev.ionfusion.fusioncli.framework.CommandSuite;
+import dev.ionfusion.fusioncli.repl.cmd.DocCmd;
 import dev.ionfusion.fusioncli.repl.cmd.ExitCmd;
 import dev.ionfusion.fusioncli.repl.cmd.ReplHelpCmd;
 import dev.ionfusion.runtime.base.FusionException;
@@ -34,8 +35,10 @@ public abstract class RepLoop
         myOut = stdout;
 
         CommandSuite commands = new CommandSuite(new ExitCmd(),
-                                                 new ReplHelpCmd());
-        ReplContext context = new ReplContext(commands, stdout);
+                                                 new ReplHelpCmd(),
+                                                 new DocCmd());
+        ReplContext context = new ReplContext(commands, myTopLevel, stdout);
+
         myCli = new ReplCli(context);
     }
 
@@ -70,7 +73,8 @@ private void welcome()
         red("\nWelcome to Fusion!\n\n");
         myOut.println("Type...");
         myOut.println("  ,exit  to exit. ^D should work too.");
-        myOut.println("  ,help  for see all REPL commands. Try `,help help`!");
+        myOut.println("  ,doc   to view documentation for a Fusion feature");
+        myOut.println("  ,help  to view a list of more REPL commands. Try `,help help`!");
         myOut.println();
     }
 

fusioncli/src/main/java/dev/ionfusion/fusioncli/repl/ReplContext.java

@@ -5,20 +5,28 @@
 
 import dev.ionfusion.fusioncli.framework.CommandContext;
 import dev.ionfusion.fusioncli.framework.CommandSuite;
+import dev.ionfusion.runtime.embed.TopLevel;
 import java.io.PrintWriter;
 
 public class ReplContext
     extends CommandContext
 {
+    private   final TopLevel    myTopLevel;
     protected final PrintWriter myOut;
 
-    public ReplContext(CommandSuite suite, PrintWriter out)
+    public ReplContext(CommandSuite suite, TopLevel topLevel, PrintWriter out)
     {
         super(suite);
+        myTopLevel = topLevel;
         myOut = out;
     }
 
 
+    public TopLevel top()
+    {
+        return myTopLevel;
+    }
+
     public PrintWriter out()
     {
         return myOut;

fusioncli/src/main/java/dev/ionfusion/fusioncli/repl/cmd/DocCmd.java

@@ -0,0 +1,130 @@
+// Copyright Ion Fusion contributors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package dev.ionfusion.fusioncli.repl.cmd;
+
+import static dev.ionfusion.fusion.FusionSyntax.isIdentifier;
+import static dev.ionfusion.fusion._Private_Trampoline.findBindingDoc;
+
+import dev.ionfusion.fusioncli.framework.Command;
+import dev.ionfusion.fusioncli.framework.Executor;
+import dev.ionfusion.fusioncli.framework.UsageException;
+import dev.ionfusion.fusioncli.repl.ReplContext;
+import dev.ionfusion.fusioncli.repl.ReplExecutor;
+import dev.ionfusion.runtime._private.doc.BindingDoc;
+import dev.ionfusion.runtime.base.FusionException;
+import dev.ionfusion.runtime.embed.TopLevel;
+import java.io.PrintWriter;
+
+public class DocCmd
+    extends Command<ReplContext>
+{
+    private static final String HELP_ONE_LINER =
+        "Print documentation for a given identifier";
+
+    private static final String HELP_USAGE =
+        "doc IDENTIFIER";
+
+    private static final String HELP_BODY =
+        "Resolves the given identifier in the current namespace and prints any associated\n" +
+        "documentation.";
+
+
+    public DocCmd()
+    {
+        super("doc");
+        putHelpText(HELP_ONE_LINER, HELP_USAGE, HELP_BODY);
+    }
+
+    @Override
+    public Executor makeExecutor(ReplContext replContext, String[] args)
+        throws UsageException
+    {
+        assert args.length < 2;
+        if (args.length == 0)
+        {
+            throw usage("Expected an identifier");
+        }
+
+        return new DocExecutor(replContext, args[0]);
+    }
+
+
+    private class DocExecutor
+        extends ReplExecutor
+    {
+        private final String myArg;
+
+        private DocExecutor(ReplContext replContext, String arg)
+        {
+            super(replContext);
+            myArg = arg;
+        }
+
+        @Override
+        public int execute()
+            throws Exception
+        {
+            Object id = determineIdentifier();
+            displayDoc(id);
+
+            return 0;
+        }
+
+        private Object determineIdentifier()
+            throws Exception
+        {
+            TopLevel top = context().top();
+
+            // TODO This assumes the normal binding of `quote_syntax`
+
+            Object stx;
+            try
+            {
+                stx = top.eval("(quote_syntax " + myArg + ")");
+            }
+            catch (FusionException e)
+            {
+                throw usage("Expected an identifier");
+            }
+
+            if (! isIdentifier(top, stx))
+            {
+                throw usage("Expected an identifier");
+            }
+
+            return stx;
+        }
+
+        private void displayDoc(Object id)
+        {
+            PrintWriter out = context().out();
+
+            BindingDoc doc = findBindingDoc(context().top(), id);
+            if (doc == null)
+            {
+                out.println("No documentation available.");
+                return;
+            }
+
+            if (doc.getKind() != null)
+            {
+                out.append("[");
+                // Using enum toString() allows display name to be changed
+                out.append(doc.getKind().toString());
+                out.append("]  ");
+            }
+            if (doc.getUsage() != null)
+            {
+                out.append(doc.getUsage());
+            }
+
+            if (doc.getBody() != null)
+            {
+                out.append('\n');
+                out.append(doc.getBody());
+                out.append('\n');
+            }
+        }
+    }
+}

fusioncli/src/main/java/dev/ionfusion/fusioncli/repl/cmd/ExitCmd.java

@@ -11,7 +11,7 @@
 public class ExitCmd
     extends Command<ReplContext>
 {
-    static final String HELP_ONE_LINER =
+    private static final String HELP_ONE_LINER =
         "Exit the REPL";
 
     private static final String HELP_USAGE =

fusioncli/src/main/java/dev/ionfusion/fusioncli/repl/cmd/ReplHelpCmd.java

@@ -15,7 +15,7 @@
 public class ReplHelpCmd
     extends Command<ReplContext>
 {
-    static final String HELP_ONE_LINER =
+    private static final String HELP_ONE_LINER =
         "Describe available REPL commands";
 
     private static final String HELP_USAGE =

fusioncli/src/test/java/dev/ionfusion/fusioncli/repl/ReplDocTest.java

@@ -0,0 +1,77 @@
+// Copyright Ion Fusion contributors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package dev.ionfusion.fusioncli.repl;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+public class ReplDocTest
+    extends ReplTestCase
+{
+    @Test
+    public void docWithoutArg()
+        throws Exception
+    {
+        supplyInput(",doc\n");
+        runRepl();
+
+        expectError("Expected an identifier");
+    }
+
+
+    @Test
+    public void docForUnbound()
+        throws Exception
+    {
+        supplyInput(",doc unbound_id\n");
+        runRepl();
+
+        // TODO Distinguish between unbound vars and undocumented bindings.
+        expectError("No documentation available.");
+    }
+
+
+    @Test
+    public void docForBuiltin()
+        throws Exception
+    {
+        supplyInput(",doc  * \n");  // Extra space is intentional.
+        runRepl();
+
+        expectResponse("Returns the product");
+    }
+
+    @Test
+    @Disabled("https://github.com/ion-fusion/fusion-java/issues/510")
+    public void docForLocal()
+        throws Exception
+    {
+        supplyInput("(define (local) '''local docs''' true)\n");
+        supplyInput(",doc local\n");
+        runRepl();
+
+        expectResponse("local docs");
+    }
+
+    @Test
+    public void docForBadSyntax()
+        throws Exception
+    {
+        supplyInput(",doc [\n");  // Extra space is intentional.
+        runRepl();
+
+        expectError("Expected an identifier");
+    }
+
+
+    @Test
+    public void docForNonIdentifier()
+        throws Exception
+    {
+        supplyInput(",doc 12\n");  // Extra space is intentional.
+        runRepl();
+
+        expectError("Expected an identifier");
+    }
+}

fusioncli/src/test/java/dev/ionfusion/fusioncli/repl/ReplTest.java

@@ -69,17 +69,6 @@ public void testFusionSyntaxError()
     }
 
 
-    @Test
-    public void testHelpHelp()
-        throws Exception
-    {
-        supplyInput("(help help)\n");
-        runRepl();
-
-        expectResponse("(help ident ...)");
-    }
-
-
     //==================================================================================
     // Basic comma-commands