NonGNU-devel ELPA - geiser-kawa


Kawa scheme support for Geiser
geiser-kawa- (.sig), 2024-Mar-31, 190 KiB
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To install this package from Emacs, use package-install or list-packages.

Full description

1. geiser-kawa

1.1. Project description

geiser-kawa adds support for Kawa Scheme to Geiser.

It has 2 parts:

  • geiser-kawa: elisp package inside the elisp directory that gives the name to the whole project.
  • kawa-geiser: included maven project written using Kawa's Java API. When it's imported from a Kawa scheme REPL, procedures needed by geiser-kawa are added to the Kawa environment.

1.2. Supported Kawa versions

Only versions of Kawa > 3.1 are supported, mostly due to the fact that before the 3.1 release some necessary Kawa classes were private.

1.3. Supported features

1.4. Unsupported features

  • geiser-related:
    • find-file
    • symbol-location
    • module-location
    • symbol-documentation
    • module-exports
    • callers
    • callees
    • generic-methods

1.5. Try geiser-kawa without modifying your emacs configuration

  1. Prerequisites:
    • java, emacs and cask available through your $PATH
    • $JAVA_HOME environment variable set
  2. Clone this repository

    git clone ""
  3. cd into the cloned dir:

    cd geiser-kawa
  4. Tell cask to install emacs dependencies:

    cask install
  5. Pull kawa-geiser's maven dependencies (the first time takes ~1 minute), compile them and start geiser-kawa's scratch buffer and repl:

    cask emacs -Q --load quickstart.el
  6. You should now have an emacs frame containing a scratch buffer in geiser-mode and a repl buffer, both with geiser-kawa support

To try geiser-kawa you need neither Maven nor Kawa:

  • mvnw (maven-wrapper) takes care of downloading a project-specific Maven version
  • kawa-geiser has Kawa's master branch as one of its dependencies. When quickstart.el calls ./mvnw package (wrapped by geiser-kawa-deps-mvnw-package), it produces a jar that includes kawa-geiser and all its dependencies, including Kawa itself.

1.6. Manual Installation

  1. Prerequisites:
    • emacs
    • java available through your $PATH
    • $JAVA_HOME environment variable set
  2. Install the geiser package in Emacs
  3. Clone this repository

    git clone ""
  4. Package java dependencies:
    1. cd into geiser-kawa
    2. run ./mvnw package
  5. Add the elisp directory inside this project to Emacs' load-path:

    (add-to-list 'load-path "<path-to-geiser-kawa/elisp>")
  6. Require geiser-kawa:

    (require 'geiser-kawa)
  7. Either:
    • Set the geiser-kawa-use-included-kawa variable to non-nil: to use the Kawa version included in geiser-kawa
    • Get Kawa and either:
      • set the geiser-kawa-binary variable
      • add kawa to $PATH
  8. Run kawa:

    M-x run-kawa

1.7. Install using MELPA

  1. Prerequisites:
    • emacs
    • java available through your $PATH
    • $JAVA_HOME environment variable set
  2. Install geiser-kawa using MELPA
  3. Package java dependencies:

    =M-x geiser-kawa-deps-mvnw-package=
  4. Require geiser-kawa

    (require 'geiser-kawa)
  5. Either:
    • Set the geiser-kawa-use-included-kawa variable to non-nil: to use the Kawa version included in geiser-kawa
    • Get Kawa and either:
      • set the geiser-kawa-binary variable
      • add kawa to $PATH
  6. Run kawa:

    M-x run-kawa

1.8. About manual lookup

To use the geiser-doc-lookup-manual feature you need a copy of the Kawa manual. You can either compile it from the Kawa source code or extract it from the pre-compiled Kawa release available on the Kawa website:

Once you have the manual in .info or .epub format, set the geiser-kawa-manual-path elisp variable to the path of the file.

1.9. About Autodoc

Double quotes around parameters: the reason why the arguments are enclosed in double quotes in autodoc is because special characters (e.g. ]) aren't read as part of a symbol by the elisp reader that geiser relies on to display autodoc data. To work-around this limitation parameters are represented by strings instead of symbols.

Parameter names: parameter names are retrieved using the gnu.bytecode package (included in Kawa) for reading local variables in Java methods' bytecode. Since parameters are not always present in bytecode as local variables (especially for methods written in Java), when not available the parameter name defaults to argN, where N is a number.

LangObjType objects: these are special objects that may behave like procedures. When these are called as procedures, a java method that returns a new object is called. This method does not have the same name as the symbol you insert in Kawa, so I thought it was a good idea to show the method name as part of the displayed module, preceded by a colon. Maybe I was wrong, in that case the behavior it's easy to change.

Autodoc for macros: not supported. I don't know how get parameters for macros in Kawa.

1.10. About completion for Java package and class members (packages, classes, methods, fields)

The whole project is in a persistent "experimental" state, but this part even more so because it's based on assumptions that:

  • I'm not sure about
  • May not hold anymore if/when the Kawa compiler changes how accessing packages and class members is represented in its AST/Expression tree

The main interactive elisp function is geiser-kawa-devutil-complete-at-point. By default, it's not bound to any key.

Supported forms (with issues) are:

  • completion for package and class names: dot notation, like in java
  • completion for field and method names:
    • field, slot-ref
    • static-field
    • invoke
    • invoke-static
    • colon notation

Unsupported forms:

  • Kawa's star-colon notation (e.g: (*:getClass "foobar"))

How it works:

  1. A region of the current buffer and cursor point inside it are sent to a Kawa procedure
  2. kawa-devutil's pattern matching is run on the resulting Expression tree
  3. If a match is found, the data is returned to Emacs

You can find some examples and known issues in kawa-devutil's README.

1.11. Extending geiser-kawa

Since you can get the result of a Kawa expression through geiser you can extend geiser-kawa blending both Elisp and Kawa, with the limitation that it's always strings that are passed back and forth. The rest of this section is an example.

Let's say we wanted to extend geiser-kawa to list all the classes available in the default classloaders.

Since kawa-geiser (the java counterpart of geiser-kawa) has kawa-devutil in its dependencies, we already have Classgraph included in kawa-geiser, shaded to by kawa-devutil itself. This means we can already traverse classpath and classloaders.

This is some simple Kawa scheme code to get a list of all the classes in the default classloaders using the ClassGraph library included in kawa-geiser:

(let* ((cg (
       (scanResult (invoke

Now we can write an interactive elisp function that evaluates the code above each time it's called and then puts the result into an emacs buffer:

(defun my-geiser-kawa-list-all-classes ()
  "A simple function that uses `geiser-kawa' to ask Kawa a list of all
the classes in the default classloaders of the current REPL and then
displays them in a dedicated buffer."
  ;; Switch to dedicated buffer and create it if it doesn't exist.
   (get-buffer-create "*geiser-kawa-classlist*"))
  ;; Clear buffer in case you already run the command once.
  (delete-region (point-min) (point-max))
  ;; Eval our Kawa code and insert result of evaluation in the buffer
  ;; we switched to above.
     ;; The same kawa code as above, quoted so that it's not evaluated
     ;; as elisp.
    '(let* ((cg (
	    (scanResult (invoke

Now every time you use M-x my-geiser-kawa-list-all-classes and have an active Kawa repl associated with the current buffer, after some seconds (there may be tenths of thousands of classes) a new buffer containing the list of available classes will be displayed.

1.12. Adding java dependencies to Kawa / Embedding kawa-geiser in your java application

The easiest way is:

  1. Create a new maven project
  2. Add to the pom.xml:
    • Your dependencies
    • Jitpack resolver:

    • kawa-geiser dependency (you can replace -SNAPSHOT with commit SHA):

  3. Start a Kawa REPL from Java (should have all the dependencies included now):

    String[] kawaArgs = new String[]{"--server", "37146"};
    Scheme scheme = new Scheme();
    scheme.eval("(require <kawageiser.Geiser>)");
  4. Use the geiser-connect command from emacs and insert the port number we specified in the previous step when prompted

1.13. Is Windows supported?

I don't usually use Windows, but it seems to work.

1.14. Difference from geiser-kawa-scheme

This project (geiser-kawa) is a translation/rewrite of geiser-kawa-scheme, which has been my first attempt at writing geiser-kawa. After geiser-kawa-scheme confirmed me that a geiser-kawa implementation was possible I decided to rewrite the Kawa side using Kawa's Java API, for the several reasons:

  • Easier to add as a scripting language in Java projects: just add the jitpack resolver and this project's repository as a dependency
  • Easier to inculde external java libraries via maven central for additional functionalities
  • Tooling for Java is excellent, tooling for Kawa is not
  • Fully static type checking: probably it's because I'm bad at programming, but it helps me a lot
  • The non-elisp part of geiser-kawa-scheme has been split in 2 projects:
    • kawa-devutil: functions that take care of getting data and general functionalities (e.g. output-capturing eval)
    • kawa-geiser:
      • maven project included in geiser-kawa
      • uses kawa-devutil's features to get relevant data and returns it as a scheme structure readable by geiser
  • Possibility to share code between kawa-devutil and other software written in Java (e.g. Kawa itself)
  • Since kawa-devutil is now a project separate from geiser-kawa, one could use it to avoid re-writing the data-getting logic if she/he wanted to implement a Kawa server for a tool other than Geiser (e.g. nrepl, jupyter, swank/slime) or a standalone Java application.

geiser-kawa VS geiser-kawa-scheme - recap table:

  geiser-kawa geiser-kawa-scheme
Kawa side written with Kawa's Java API Kawa Scheme
I'm going to add more features Probably yes Probably not

Old versions

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