babashka/doc/dev.md

Developing Babashka

You need lein for running JVM tests and/or producing uberjars. For building binaries you need GraalVM. Currently we use java8-19.3.1.

Clone repository

To work on Babashka itself make sure Git submodules are checked out.

$ git clone https://github.com/borkdude/babashka --recursive

To update later on:

$ git submodule update --recursive

REPL

lein repl will get you a standard REPL/nREPL connection. To work on tests use lein with-profiles +test repl.

Adding libraries and classes

When adding libraries to babashka, consider these evaluation criteria:

• Adding the library or class extends the reach of babashka to more libraries in the Clojure eco-system.
• The library or class useful for general purpose scripting or accomplishing useful devops tasks.
• The functionality can't be met by shelling out to another CLI or can't be written as a small layer over an existing CLI (like babashka.curl) instead.

If none of the criteria are met, but adding a feature is still useful to a particular company or niche audience, it can still be added when hidden behind a feature flag. This is the case for next.jdbc and the PostgresQL and HSQLDB database drivers. Companies interested in these features can compile an instance of babashka themselves, instead of using the standard distributed version.

Adding classes

Add necessary classes to babashka/impl/classes.clj. For every addition, write a unit test, so it's clear why it is added and removing it will break the tests. Try to reduce the size of the binary by only adding the necessary parts of a class in :instance-check, :constructors, :methods, :fields or :custom.

The reflection.json file that is needed for GraalVM compilation is generated with:

lein with-profiles +reflection run

Test

Test on the JVM (for development):

script/test

Test the native version:

BABASHKA_TEST_ENV=native script/test

Build

See build.md.

JDBC

Findings from various experiments with JDBC drivers in babashka:

• Postgres: adds 3MB to the binary. It seems the maintainers have put in effort to make the driver compatible with Graal. The driver is part of bb since v0.0.89.
• Sqlite: I feel like I'm close to a working solution, but it hangs. It adds 20MB to the binary. Since sqlite has a nice CLI we could also just shell out to it (there's an example in the examples dir). We could also build a babashka.sqlite namespace around the CLI maybe similar to babashka.curl. See #385 for details.
• HSQLDB: easy to get going with Graalvm. Adds 10 MB to the binary. It's under a feature flag right now on master. See build.md for details. Derby and H2 are known to not work with GraalVM, so far this is the "best" embedded option from a Graal perspective. Setting the -Xmx value for Docker to 4500m got it to crash. 4800m did work, but it took 17 minutes (compared to 10 minutes without this feature).
• MySQL / MariaDB: can't get those to work yet. Work in progress in issue #387.

To progress work on sqlite and mySQL, I need a working Clojure example. If you want to contribute, consider making a an example Clojure GraalVM CLI that puts something in a sqlite / mysql DB and reads something from it.

Binary size

Keep notes here about how adding libraries and classes to Babashka affects the binary size. We're registering the size of the macOS binary (as built on CircleCI).

2020/04/23 Added next.jdbc and postgres JDBC driver: (- 51019836 48099780) = 2920kb added

2020/04/23 Added BigDecimal (- 48103868 47857732) = 246kb added

2020/04/18 Added clojure.data.xml 47808572 - 45923028 = 1886kb added.

2020/03/29 Added clj-yaml for parsing and generating yaml. 45196996 - 42626884 = 2570kb added.

2020/03/28 Added java.nio.file.FileSystem(s) to support extracting zip files 42562284 - 42021244 = 541kb added.

2020/03/22 Added java.io.FileReader 42025276 - 42008876 = 16kb added.

2020/03/20 Added transit write, writer, read, reader 42004796 - 41025212 = 980kb added (305kb zipped).

2020/03/19 Added java.lang.NumberFormatException, java.lang.RuntimeException, java.util.MissingResourceException and java.util.Properties to support cprop. 41025180 - 40729908 = 295kb added.

2020/02/21 Added java.time.temporal.ChronoUnit 40651596 - 40598260 = 53kb added.

2020/02/19, e43727955a Added fipp.edn/pprint 40598268 - 39744804 = 853kb added.

2020/02/09, c8fd1c7931 Added java.lang.BigInteger and java.security.MessageDigest. 39281972 - 39072764 = 209kb added.

2020/04/02 v0.0.69 38883676

2020/01/24, 43eef7075f: 38.3mb, 11.1mb zipped Added hierarchies (derive, isa?, etc).

2020/01/23, 485fef7df5: 37.4mb / 10.9mb zipped Added: StringBuilder, java.io.{Reader,Writer,PrinterWriter,PushbackReader}

2020/01/08, 303ca9e825: 36.9mb / 10.8mb zipped

Removing cheshire from bb: 36.2mb / 10.5mb zipped.