Expand description
Cargo’s config system.
The Config object contains general information about the environment,
and provides access to Cargo’s configuration files.
Config value API
The primary API for fetching user-defined config values is the
Config::get method. It uses serde to translate config values to a
target type.
There are a variety of helper types for deserializing some common formats:
value::Value: This type provides access to the location where the config value was defined.ConfigRelativePath: For a path that is relative to where it is defined.PathAndArgs: Similar toConfigRelativePath, but also supports a list of arguments, useful for programs to execute.StringList: Get a value that is either a list or a whitespace split string.
Map key recommendations
Handling tables that have arbitrary keys can be tricky, particularly if it
should support environment variables. In general, if possible, the caller
should pass the full key path into the get() method so that the config
deserializer can properly handle environment variables (which need to be
uppercased, and dashes converted to underscores).
A good example is the [target] table. The code will request
target.$TRIPLE and the config system can then appropriately fetch
environment variables like CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER.
Conversely, it is not possible do the same thing for the cfg() target
tables (because Cargo must fetch all of them), so those do not support
environment variables.
Try to avoid keys that are a prefix of another with a dash/underscore. For
example build.target and build.target-dir. This is OK if these are not
structs/maps, but if it is a struct or map, then it will not be able to
read the environment variable due to ambiguity. (See ConfigMapAccess for
more details.)
Internal API
Internally config values are stored with the ConfigValue type after they
have been loaded from disk. This is similar to the toml::Value type, but
includes the definition location. The get() method uses serde to
translate from ConfigValue and environment variables to the caller’s
desired type.
Structs
Configuration for build.target.
Configuration information for cargo. This is not specific to a build, it is information relating to cargo itself.
Internal error for serde errors.
Key for a configuration variable.
Use with the get API to fetch a string that will be converted to a
PathBuf. Relative paths are converted to absolute paths based on the
location of the config file.
A config type that is a program to run.
A type to deserialize a list of strings from a toml file.
Config definition of a [target.'cfg(…)'] table.
Config definition of a [target] table or [host].
StringList automatically merges config values with environment values, this instead follows the precedence rules, so that eg. a string list found in the environment will be used instead of one in a config file.
A type which can be deserialized as a configuration value which records where it was deserialized from.
Enums
Location where a config value is defined.
Configuration for ssl-version in http section
There are two ways to configure: