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Dependencies

LuaRocks handles dependencies on Lua modules — rocks can specify other rocks it depends on, and attempts to fulfill those dependencies at install time. A rock will only be installed if all its dependencies can be fulfilled.

LuaRocks also supports verification of dependencies on external libraries. A rock can specify an external package it depends on (for example, a C library), and give to LuaRocks hints on how to detect if it is present, typically as C header or library filenames. LuaRocks then looks for these files in a pre-configured search path and, if found, assumes the dependency is fulfilled. If not found, an error message is reported and the user can then install the missing external dependency (using the tools provided by their operating system) or inform LuaRocks of the location of the external dependency in case it was installed and LuaRocks failed to find it.

Dependencies of a rock are specified in its rockspec file. See the complete specification of the dependency syntax in the Rockspec format page and examples in rockspec files of the public rocks server.

Dependency modes

Since 2.0.12, the LuaRocks command-line tool supports different "dependency modes". These are useful to specify how it should behave on the presence of multiple rocks trees specified in the config file:

  • one
  • all
  • order
  • none

This can be set through the configuration file, using the string variable deps_mode (example: deps_mode="order") or through the command-line, using the --deps-mode flag (example: --deps-mode=order).

one

This is the default, conservative behavior. LuaRocks only takes one rocks tree into account when checking dependencies. For example, if you have two rocks trees configured (rocks_trees={home.."/.luarocks", "/usr"}) and you try to install a rock in $HOME/.luarocks, it will check that all required dependencies are installed _in that tree_. If the dependency rock is already installed under /usr, it will ignore that copy.

This is conservative because it ensures that a rock and all its dependencies are installed under the same tree. So, if another user modifies the other tree, there's no risk that the rock installed in your home tree might stop working.

all

LuaRocks scans all configured rocks trees to search for dependencies. If the required rock for a dependency is available in any tree, it will consider that dependency fulfilled, and will not install that again.

However, note for example that if you install a rock in /usr and its dependency was installed in your $HOME tree, the installed rock will work for your user account (which has access to the /usr tree and your home tree), but will probably not work for other users, if they don't have a compatible dependency installed in their own home trees.

order

LuaRocks uses the order of the list of rocks trees to determine if a rocks tree should be used as a valid provider of dependencies or not. LuaRocks will only use rocks from either the tree it is installing to, or trees that appear below the rock that's in use in the rocks_trees array. So, if your rocks_trees array looks like {home.."/.luarocks", "/usr/local", "/usr"}, installing a rock under your $HOME directory will accept dependencies from any of the three trees. Installing into /usr/local will use dependencies from /usr but not from the $HOME directory. Installing into /usr will use rocks from that tree only.

So, by carefully ordering your array of rocks trees in the configuration file, you can use the same configuration file for both your administrator account and your regular user account.

Note, however, that like in the "all" mode, an administrator can break a rock you installed in your home account by removing a dependency rock from the global tree.

none

LuaRocks does not use any tree, or install any dependencies. This means, of course, that installed rocks may be installed with missing dependencies and may simply not work. This mode is not recommended for general use, but it is useful in some specific scenarios (incorrect dependencies, batch recompilation, etc.)

This is equivalent to the old --nodeps option.

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