218 lines
11 KiB
Markdown
218 lines
11 KiB
Markdown
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
|
||
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
|
||
**Table of Contents** *generated with [DocToc](https://github.com/thlorenz/doctoc)*
|
||
|
||
- [FAQ](#faq)
|
||
|
||
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
|
||
|
||
# FAQ
|
||
|
||
**Q:** How do you pronounce Leiningen?
|
||
**A:** It's LINE-ing-en. ['laɪnɪŋən]
|
||
|
||
**Q:** What's a group ID? How do snapshots work?
|
||
**A:** See the
|
||
[tutorial](https://github.com/technomancy/leiningen/blob/stable/doc/TUTORIAL.md)
|
||
for background.
|
||
|
||
**Q:** How should I pick my version numbers?
|
||
**A:** Use [semantic versioning](http://semver.org).
|
||
|
||
**Q:** What if my project depends on jars that aren't in any repository?
|
||
**A:** You will need to get them in a repository. The
|
||
[deploy guide](https://github.com/technomancy/leiningen/blob/stable/doc/DEPLOY.md)
|
||
explains how to set up a private repository. In general it's easiest
|
||
to deploy them to a static HTTP server or a private S3 bucket. Once
|
||
the repo is set up, `lein deploy private-repo com.mycorp/somejar
|
||
1.0.0 somejar.jar pom.xml` will push the artifacts out. If you don't
|
||
have a pom, you can create a dummy project with `lein new` and
|
||
generate a pom from that. If you are just doing exploratory coding
|
||
you can deploy to `file:///$HOME/.m2/repository` and the jars will
|
||
be available locally.
|
||
|
||
**Q:** I want to hack a project and one of its dependencies, but it's annoying to switch between them.
|
||
**A:** Leiningen provides a feature called *checkout dependencies* to
|
||
make this smoother. See the
|
||
[tutorial](https://github.com/technomancy/leiningen/blob/stable/doc/TUTORIAL.md)
|
||
to learn more.
|
||
|
||
**Q:** Is it possible to exclude indirect dependencies?
|
||
**A:** Yes. Some libraries, such as log4j, depend on projects that are
|
||
not included in public repositories and unnecessary for basic
|
||
functionality. Projects listed as `:dependencies` may exclude
|
||
any of their dependencies by using the `:exclusions` key. See
|
||
`lein help sample` for details.
|
||
|
||
**Q:** I specified a dependency on version X but am getting version Y; what's up?
|
||
**A:** One of your dependencies' dependencies has declared a
|
||
dependency on a hard version range, which overrides your "soft"
|
||
declaration. Running `lein deps :tree` will identify which of your
|
||
dependencies are responsible for the version range. You can add an
|
||
`:exclusions` clause to prevent that from affecting the rest of your
|
||
dependencies. See `lein help sample` for how exclusions work. You
|
||
may also want to report a bug with the dependency that uses hard
|
||
version ranges as they cause all kinds of problems and exhibit
|
||
unintuitive behaviour.
|
||
|
||
**Q:** I have two dependencies, X and Y, which depends on Z. How is the version
|
||
of Z decided?
|
||
**A:** The decision depends on which depth and which order the dependencies come
|
||
in the `:dependencies` vector: The dependency at the lowest depth will be
|
||
picked. If there are multiple versions of a single group/artifact at that
|
||
depth, the first of those will be picked. For instance, in the dependency
|
||
graph
|
||
|
||
[Z "1.0.9"]
|
||
[X "1.3.2"]
|
||
[Z "2.0.1"]
|
||
|
||
the direct dependency (`[Z "1.0.9"]`) is picked, as it is closest to the root.
|
||
For the dependency graph
|
||
|
||
[X "1.3.2"]
|
||
[Z "2.0.1"]
|
||
[Y "1.0.5"]
|
||
[Z "2.1.3"]
|
||
|
||
the dependency X comes first, and therefore `[Z "2.0.1"]` is picked. If we
|
||
place Y before X however, `[Z "2.1.3"]` will be picked.
|
||
|
||
Note that this only applies to soft dependencies, and `lein deps :tree` will
|
||
only warn if the latest version is not chosen.
|
||
|
||
**Q:** I'm behind an HTTP proxy; how can I fetch my dependencies?
|
||
**A:** Set the `$http_proxy` environment variable in Leiningen 2.x. You can also
|
||
set `$http_no_proxy` for a list of hosts that should be reached directly, bypassing
|
||
the proxy. This is a list of patterns separated by `|` and may start or end with
|
||
a `*` for wildcard, e.g. `localhost|*.mydomain.com`.
|
||
For Leiningen 1.x versions, see the instructions for
|
||
[configuring a Maven proxy](http://maven.apache.org/guides/mini/guide-proxies.html)
|
||
using `~/.m2/settings.xml`.
|
||
|
||
**Q:** What can be done to speed up launch?
|
||
**A:** The main delay involved in Leiningen comes from starting two
|
||
JVMs: one for your project and one for Leiningen itself. Most people
|
||
use a development cycle that involves keeping a single project REPL
|
||
process running for as long as they're working on that project.
|
||
Depending on your editor you may be able to do this via its Clojure
|
||
integration. (See [nrepl.el](https://github.com/clojure-emacs/cider) or
|
||
[fireplace](https://github.com/tpope/vim-fireplace), for example.)
|
||
Otherwise you can use the basic `lein repl`.
|
||
|
||
**Q:** Still too slow; what else can make startup faster?
|
||
**A:** The wiki has a page covering
|
||
[ways to improve startup time](https://github.com/technomancy/leiningen/wiki/Faster).
|
||
|
||
**Q:** What if I care more about long-term performance than startup time?
|
||
**A:** Leiningen 2.1.0 onward get a speed boost by disabling optimized
|
||
compilation (which only benefits long-running processes). This can
|
||
negatively affect performance in the long run, or lead to inaccurate
|
||
benchmarking results. If want the JVM to fully optimize, you can
|
||
you can switch profiles with `lein with-profiles production run ...`.
|
||
|
||
**Q:** What does "Unrecognized VM option 'TieredStopAtLevel=1'" mean?
|
||
**A:** Old versions of the JVM do not support the directives Leiningen
|
||
uses for tiered compilation which allow the JVM to boot more
|
||
quickly. You can disable this behaviour with `export LEIN_JVM_OPTS=`
|
||
or upgrade your JVM to something more recent. (newer than b25 of Java 6)
|
||
|
||
**Q:** I'm attempting to run a project as a background process (`lein run &`),
|
||
but the process suspends until it is in the foreground. How do I run a program
|
||
in the background?
|
||
**A:** For long-lasting processes, it's better to create an uberjar
|
||
and run that or use `lein trampoline run &`. For short-lived ones,
|
||
both `lein run <&- &` and `bash -c "lein run &"` will work fine.
|
||
|
||
**Q:** I'm getting "could not transfer artifact ... peer not authenticated"
|
||
**A:** This means that either your JVM is not configured with the
|
||
correct certificate authorities, or you're experiencing a
|
||
[man-in-the-middle attack](https://github.com/technomancy/leiningen/issues/1028#issuecomment-32732452)
|
||
on your SSL connection. Leiningen ships with the current Clojars
|
||
public certificate at the time of this writing, so you should be
|
||
able to work around problems with your CA by putting `:certificates
|
||
["clojars.pem"]` in your `:user` profile, assuming the certificate
|
||
that ships with Leiningen hasn't expired.
|
||
|
||
**Q:** How do I determine my project's version at runtime?
|
||
**A:** Leiningen writes a file called `pom.properties` into
|
||
`target/classes` which contains a the version number and current git
|
||
revision of the project. In previous versions of Leiningen this was
|
||
only available when running from jar files, but as of 2.4.1 it's
|
||
available during `lein run ...`, etc. You can read it by running
|
||
this code (replace "group" and "artifact" with values appropriate to
|
||
your project):
|
||
|
||
```clj
|
||
(with-open [pom-properties-reader (io/reader (io/resource "META-INF/maven/group/artifact/pom.properties"))]
|
||
(doto (java.util.Properties.)
|
||
(.load pom-properties-reader)))
|
||
```
|
||
|
||
**Q:** How can I read my project map at runtime?
|
||
**A:** Usually you do not need the complete project map, only a specific subset
|
||
of some values. If you want different configuration based on different tasks,
|
||
then [environ](https://github.com/weavejester/environ) is probably a good fit.
|
||
If you want information like the project's version number or git revision,
|
||
read the question and answer above.
|
||
|
||
Generally those solutions are sufficient, but if you need more than this, you
|
||
should rather read the `project.clj` yourself. The project map changes based
|
||
on the task you use, and so different tasks (repl, jar, uberjar to name a few)
|
||
will make it hard to make the testing- and production project map identical.
|
||
To add `project.clj` to your classpath, you can add in
|
||
[lein-shell](https://github.com/hyPiRion/lein-shell) and prepend `:prep-tasks`
|
||
with `["shell" "cp" "project.clj" "resources/project.clj"]` and read it
|
||
through e.g.
|
||
|
||
```clj
|
||
(read-string (slurp (io/resource "project.clj")))
|
||
```
|
||
|
||
**Q:** I need to do AOT for an uberjar; can I avoid it during development?
|
||
**A:** A reasonable request. Leiningen supports isolating different
|
||
profiles by their target directory. Simply specify `:target-path
|
||
"target/%s"` in order to have each profile set use a different
|
||
directory for generated files. Then you can put your `:aot`
|
||
settings in the `:uberjar` profile, and the .class files created
|
||
from the AOT process will not affect normal development use. You can
|
||
specify the profile-isolated `:target-path` in your `:user` profile if
|
||
you want it applied across all the projects you work on.
|
||
|
||
**Q:** Is there a way to use an uberjar without AOT?
|
||
**A:** As of Leiningen 2.4.0, if you omit `:main` in `project.clj`,
|
||
your uberjars will use `clojure.main` as their entry point. You can
|
||
launch with `java -jar my-app-standalone.jar -m my.entry.namespace
|
||
arg1 arg2 [...]` without any AOT, but it will take longer to launch.
|
||
|
||
**Q:** Why does `lein jar` package some namespaces from dependencies into my jar?
|
||
**A:** This is likely because you want to AOT-compile namespaces. Any
|
||
AOT-compiled namespace can only depend on AOT-compiled namespaces. Therefore,
|
||
if you depend on a namespace in a dependency that is not AOT-compiled, it will
|
||
be AOT-compiled and bundled with the jar.
|
||
|
||
**Q:** I'd like to have certain config active only on a certain OS.
|
||
**A:** You can do this by using unquote in the `:dev` profile:
|
||
|
||
```clj
|
||
:profiles {:dev [:dev/all ~(leiningen.core.utils/get-os)]
|
||
:dev/all {...}
|
||
:linux {...}
|
||
:windows {...}
|
||
:macosx {...}}
|
||
```
|
||
|
||
You can also check things like `(System/getProperty
|
||
"java.specification.version")` to use the JVM version or any other
|
||
property.
|
||
|
||
**Q:** I get a `java.security.KeyException` or `sun.security.provider.certpath.SunCertPathBuilderException` when running `lein`
|
||
**A:** The `java.security.KeyException` indicates an ssl error when trying to communicate with the HTTPS server via Java. This could be because you need to update the JDK, or some other package (e.g. with old versions of the nss package).
|
||
|
||
* On Fedora, you might just try running a `sudo yum update` to update all of your packages or `sudo yum update nss`.
|
||
* On Debian/Ubuntu, `sudo update-ca-certificates -f` might help, or `sudo /var/lib/dpkg/info/ca-certificates-java.postinst configure`
|
||
* You should also check your system clock and make sure the time is accurate; it's possible to run into SSL connection failures if your clock is way out of sync.
|
||
* If it still doesn't work, please see if any of [these 'ssl' labelled issues](https://github.com/technomancy/leiningen/issues?utf8=%E2%9C%93&q=is%3Aissue%20label%3Assl%20) might help
|
||
|
||
**Q:** `lein`/`lein.bat` won't download `leiningen-x.y.z-SNAPSHOT.jar`
|
||
**A:** You probably downloaded `lein`/`lein.bat` from the [master branch](https://github.com/technomancy/leiningen/tree/master/bin). Unless you plan to build leiningen yourself or help develop it, we suggest you use the latest stable version: [lein](https://raw.githubusercontent.com/technomancy/leiningen/stable/bin/lein)/[lein.bat](https://raw.githubusercontent.com/technomancy/leiningen/stable/bin/lein.bat)
|