[JGIT PATCH 17/28] Support automatic command line parsing for TextBuiltin subclasses

[JGIT PATCH 17/28] Support automatic command line parsing for TextBuiltin subclasses

[Shawn O. Pearce]

By default the execute method will parse the supplied arguments
and then invoke run().  Newer style builtins will override the
run method, rather than the execute method, and take advantage of
the standard parsing support.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
---
 .../src/org/spearce/jgit/pgm/TextBuiltin.java      |   69 +++++++++++++++++++-
 1 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/org.spearce.jgit.pgm/src/org/spearce/jgit/pgm/TextBuiltin.java b/org.spearce.jgit.pgm/src/org/spearce/jgit/pgm/TextBuiltin.java
index 0f39f11..c4a55f4 100644
--- a/org.spearce.jgit.pgm/src/org/spearce/jgit/pgm/TextBuiltin.java
+++ b/org.spearce.jgit.pgm/src/org/spearce/jgit/pgm/TextBuiltin.java
@@ -43,9 +43,13 @@ import java.io.IOException;
 import java.io.OutputStreamWriter;
 import java.io.PrintWriter;
 
+import org.kohsuke.args4j.CmdLineException;
+import org.kohsuke.args4j.Option;
 import org.spearce.jgit.lib.Constants;
 import org.spearce.jgit.lib.ObjectId;
 import org.spearce.jgit.lib.Repository;
+import org.spearce.jgit.pgm.opt.CmdLineParser;
+import org.spearce.jgit.revwalk.RevWalk;
 
 /**
  * Abstract command which can be invoked from the command line.
@@ -67,12 +71,18 @@ public abstract class TextBuiltin {
 
 	private String commandName;
 
+	@Option(name = "--help", usage = "display this help text", aliases = { "-h" })
+	private boolean help;
+
 	/** Stream to output to, typically this is standard output. */
 	protected PrintWriter out;
 
 	/** Git repository the command was invoked within. */
 	protected Repository db;
 
+	/** RevWalk used during command line parsing, if it was required. */
+	protected RevWalk argWalk;
+
 	/**
 	 * Set the name this command can be invoked as on the command line.
 	 * 
@@ -94,7 +104,7 @@ public abstract class TextBuiltin {
 	}
 
 	/**
-	 * Perform the action(s) of this command.
+	 * Parse arguments and run this command.
 	 * 
 	 * @param args
 	 *            command line arguments passed after the command name.
@@ -103,7 +113,62 @@ public abstract class TextBuiltin {
 	 *             framework will catch the exception and print a message on
 	 *             standard error.
 	 */
-	public abstract void execute(String[] args) throws Exception;
+	public void execute(String[] args) throws Exception {
+		parseArguments(args);
+		run();
+	}
+
+	/**
+	 * Parses the command line arguments prior to running.
+	 * <p>
+	 * This method should only be invoked by {@link #execute(String[])}, prior
+	 * to calling {@link #run()}. The default implementation parses all
+	 * arguments into this object's instance fields.
+	 * 
+	 * @param args
+	 *            the arguments supplied on the command line, if any.
+	 */
+	protected void parseArguments(final String[] args) {
+		final CmdLineParser clp = new CmdLineParser(this);
+		try {
+			clp.parseArgument(args);
+		} catch (CmdLineException err) {
+			if (!help) {
+				System.err.println("fatal: " + err.getMessage());
+				System.exit(1);
+			}
+		}
+
+		if (help) {
+			System.err.print("jgit ");
+			System.err.print(commandName);
+			clp.printSingleLineUsage(System.err);
+			System.err.println();
+
+			if (help) {
+				System.err.println();
+				clp.printUsage(System.err);
+				System.err.println();
+			}
+			System.exit(1);
+		}
+
+		argWalk = clp.getRevWalkGently();
+	}
+
+	/**
+	 * Perform the actions of this command.
+	 * <p>
+	 * This method should only be invoked by {@link #execute(String[])}.
+	 * 
+	 * @throws Exception
+	 *             an error occurred while processing the command. The main
+	 *             framework will catch the exception and print a message on
+	 *             standard error.
+	 */
+	protected void run() throws Exception {
+		throw die("Override either execute (legacy) or run (new style).");
+	}
 
 	/**
 	 * @return the repository this command accesses.
-- 
1.5.6.3.569.ga9185

Re: [JGIT PATCH 17/28] Support automatic command line parsing for TextBuiltin subclasses

[Florian Köberle]

Hi Shawn

to use args4j was really a great idea. I had a patch, implementing
something similar to args4j in my repository, but using a library is
always better. *thumb up*


I had a short look at the files and noticed that the inner "if (help) {"
is unnecessary:

+		if (help) {
+			System.err.print("jgit ");
+			System.err.print(commandName);
+			clp.printSingleLineUsage(System.err);
+			System.err.println();
+
+			if (help) {
+				System.err.println();
+				clp.printUsage(System.err);
+				System.err.println();
+			}
+			System.exit(1);
+		}

Also a cool function which you may want to use is:

public <U> Class<? extends U> asSubclass(Class<U> clazz)

With that method of Class<?> you can do the cast before you actually
create the object.
You could for example make use of them in SubcommandHandler:
l. 124			cmd = (TextBuiltin) cons.newInstance();

Best regards,
Florian Köberle

Re: [JGIT PATCH 17/28] Support automatic command line parsing for TextBuiltin subclasses

[Shawn O. Pearce]

Florian KKKberle <FloriansKarten@web.de> wrote:
> I had a short look at the files and noticed that the inner "if (help) {"
> is unnecessary:
>
> +		if (help) {
> +			System.err.print("jgit ");
> +			System.err.print(commandName);
> +			clp.printSingleLineUsage(System.err);
> +			System.err.println();
> +
> +			if (help) {

Gaaah.  Good catch, thanks.  I copied and pasted that block from the
global option parser to the per-command parser, and then refactored
it a little and missed removing this unnecessary inner if test.
I'll fix with a rebase.

-- 
Shawn.