enrich-classpath

A library (and Leiningen plugin) that, as its main feature, automatically downloads all available .jars with Java sources and javadocs for a given project, so that various tooling (typically IDEs) can access it.

It behaves gracefully even in face of :managed-dependencies, :pedantic?, in- and inter-process parallel invocations of Lein, etc.

For efficiency, it has caching that is shared across projects, and dependency resolution is parallel.

Importantly, it does not mutate the classpath via classloaders in any way, yielding a simple solution that guaranteed to work across all JDKs.

This is the set of things that enrich-classpath can add to the classpath, when needed (depending on your JDK and build tool of choice):

• third-party source/javadocs .jars
• the sources for a given JDK
  • e.g. the sources for the Thread class.
• the :java-source-paths from a Leiningen project
  • this way, IDE-like functionality will also work for classes you might be developing.
• tools.jar.

A sample use case

As a quick example of you can do with it:

(defn class->source [class-object]
  {:pre [(class? class-object)]}
  (-> class-object pr-str munge (string/replace "." "/") (str ".java") (io/resource) slurp))

;; Usage: (-> Thread class->source println)

All what the plugin does is placing a source (and/or javadoc) .jar in the classpath, so that (io/resource) will return it (else it would return nil).

A great real-world lib that would be enhanced by this program is Orchard's source-info.

Installation prerequisites

• If using cider-nrepl, the minimum required version is 0.26.0.
• If using Orchard, the minimum required version is 0.7.1.

Installation and usage

Leiningen

Add the following somewhere in your ~/.lein/profiles.clj (aka your user-wide profile):

;; Installing this plugin under the :repl profile is most recommended for best performance,
;; especially if you work with a monorepo with a complex build process.  
:repl {:middleware [cider.enrich-classpath/middleware]
       :plugins    [[mx.cider/enrich-classpath "1.15.2"]]
       ;; Optional - you can use this option to specify a different set (e.g. a smaller set like #{"sources"} is more performant)
       :enrich-classpath {:classifiers #{"sources" "javadoc"}}}

If adding this middleware on a per-project basis, make sure it's not turned on by default, simply because other people might not appreciate a slower (first) dependency resolution for a functionality that they might not use. Profiles help.

After that, lein repl and similar commands will download each artifact of your dependency tree with "sources" and "javadoc" Maven classifiers, if such an artifact exists (normally these only exist for Java dependencies, not Clojure ones), and place it in the classpath for your REPL process.

tools.deps

enrich-classpath has a distinct artifact intended for tools.deps usage:

mx.cider/tools.deps.enrich-classpath {:mvn/version "1.15.2"}

Usage is still TBD.

Notes on caching

Running this program for the first time on a given project will be slow (think: anything between 1-3m). The more dependencies your project has, especially Java ones, the slower this run will be.

Each time a source or javadoc .jar is found, the found artifact will be logged, so that you can see that the program is in fact doing something:

:cider.enrich-classpath/found [org.clojure/clojure "1.10.1" :classifier "sources"]

After a successful run, a cache file is written to ~/.enrich-classpath-cache. This file is shared across all projects, and will automatically grow via merge. So the first few runs in a variety of projects will result in a slow dependency resolution, and after that it will stabilize in those projects (and best-case scenario, also in other projects)

Given a project with 100% cache hits (which eventually will be the case in all your projects, after a while), this program's runtime overhead will be essentially zero.

The ~/.enrich-classpath-cache file has a stable format. You can version-control it, so that if you setup a new machine you won't have cache misses.

Options

This program observes a number of Lein configuration options under the :enrich-classpath key:

:shorten

Default: false.

If true, most classpath entries will be added as a single, very thin .jar file, which contents will consist of a single MANIFEST.MF file which will point of all those classpath entries.

This results in a shorter java process name, which avoids incurring into the length limitations that Linux programs can be subject to.

There isn't a visible difference in behavior around using this option: with or without it, entries will be added to the classpath effectively in the same way, and e.g. clojure.java.io/resource will keep pointing to the right jar (i.e. the final one, not the thin one that points to it).

:classifiers

By default, both sources and javadocs will be fetched. By specifying only sources to be fetched, one gets a 2x performance improvement (because 0.5x as many items will be attempted to be resolved):

:enrich-classpath {:classifiers #{"sources"}}

You can also specify classifiers other than "sources", "javadoc", if that is useful to you.

:failsafe

By default, this program runs within a try/catch block and within a timeout. This wrapping is called the 'failsafe' and it has the goal of preventing the plugin from possibly disrupting REPL/IDE startup.

If an error or timeout occurs, REPL startup will continue, although no entries will be added to the classpath.

Generally you want to keep this default. By specifying :failsafe false, you can disable this wrapping, which might ease troubleshooting.

:timeout

This is the timeout value in seconds that :failsafe uses. It defaults to 215.

:repositories

The Maven repositories that this program will query, in search of sources and javadocs.

Defaults to your project's Lein :repositories, typically Maven Central + Clojars + any custom repositories you may have specified.

If you specify :repositories, they will replace Lein's entirely.

In all cases, repositories detected as unreachable (because of DNS, auth, etc) will be removed.

Troubleshooting

If this program is not behaving as it should, you can debug it in isolation with the following command:

DEBUG=true lein with-profile +repl deps

The following entries can be possibly logged:

• :cider.enrich-classpath/resolving - a request is being performed for resolving a specific dependency (of any kind: plain, source or javadoc)
• :cider.enrich-classpath/found - a source/jar artifact has been found, and will be added to the classpath.
• :cider.enrich-classpath/resolved - a request has succeeded in resolving a specific dependency (of any kind: plain, source or javadoc)
• :cider.enrich-classpath/timed-out - a given dependency request has timed out, or the program as a whole has timed out (per the :failsafe option).
• :cider.enrich-classpath/failed-to-resolve - the request for resolving a given dependency failed.
• :cider.enrich-classpath/omitting-empty-source - a given source artifact (.jar) was found, but it didn't have actual Java sources in it, so it won't be added to the classpath.
• :cider.enrich-classpath/no-jdk-sources-found - no JDK sources could be found. Your JDK distribution (on apt, rpm, etc) probably didn't include any sources, and they should be installed separately (e.g. sudo apt install openjdk-11-source).

If you wish to start from a clean slate (given that resolutions are cached, even in face of timeout), you can remove the ~/.enrich-classpath-cache file.

License

This program and the accompanying materials are made available under the terms of the Eclipse Public License 2.0.