JUST GRAPH FILE(5) | File Formats Manual()

NAME
just-graph-file - The format of the action graph used by justbuild(1)

DESCRIPTION
The file is read as JSON. Any other serialization describing the same JSON object is equivalent. We assume, that in JSON objects, each key occurs at most once; it is implementation defined how repetitions of the same key are treated.

  Artifacts and their serialization
There are four different kind of artifacts. The serialization of the artifact is always a JSON object with two keys: "type" and "data". The value for "type" is always on of the strings "LOCAL", "KNOWN", "ACTION", or "TREE". The value for "data" is a JSON object with keys depending on which type the artifact is of.

•   "LOCAL" artifacts refer to source files in a logical repository. The describing data are

    •   the "repository", given as its global name, and

    •   the "path", given as path relative to the root of that repository.

•   "KNOWN" artifacts are described by the hash of their content. The describing data are

    •   the "file_type", which is a one-letter string,

        •   "f" for regular, non-executable files,

        •   "x" for executable files, or

        •   "t" for trees.

    •   the "id" specifying the (applicable) hash of the file given as its hexadecimal encoding, a string, and

    •   the "size" of the artifact, a number, in bytes.

•   "ACTION" artifacts are the outputs of actions. The defining data are

    •   the "id", a string with the name of the action, and

    •   the "path", specifying the path of this output artifact, relative to the root of the action directory

•   "TREE" artifacts refer to trees defined in the action graph. The defining data are

    •   the "id", a string with the name of the tree.

  Actions and their serialization
Actions are given by the data described in the following sections. For each item a key is associated and the serialization of the action is a JSON object mapping those keys to the respective serialization of the values. For some data items default values are given; if the value for the respective item equals the default, the respective key-value pair may be omitted in the serialization.

•   "command" specifies the command to be executed. It is a non-empty list of strings that forms the argument vector; the first entry is taken as program. This key is mandatory.

•   "env" specifies the environment variables the command should be executed with. It is given as map from strings to strings. The default is the empty map.

•   "input" describes the files available to the action. The action must not modify them in any way. They are specified as map from paths to artifacts (the latter serialized as described). Paths have to be relative paths and are taken relative to the working directory of the action. The default is the empty map.

•   "output" describes the files the action is supposed to generate, if any. It is given as a list of strings, each specifying a file name by a path relative to the working directory of the action. The default is the empty list. However, every action has to produce some form of output, so if "output" is empty, "output_dirs" cannot be empty.

•   "output_dirs" describes the directory output of the action, if any. It is given as a list of strings, each specifying the a directory name by a path relative to the working directory of the action. The "output_dirs" may also specify directories from which individual files are specified as "output". The default value for "output_dirs" is the empty list. However, every action to produce some form of output, so if "output_dirs" is empty, "output" cannot be empty.

•   "may_fail" can either be null or a string. If it is a string, the build should be continued, even if that action returns a non-zero exit state. If the action returns a non-zero exit code, that string should be shown to the user in a suitable way (e.g., printing on the console). Otherwise (i.e., if no "may_fail" string is given), the build should be aborted if the action returns a non-zero exit code. The default for "may_fail" is null, i.e., abort on non-zero exit code.

•   "no_cache" is a boolean. If true, the action should never be cached, not even on success. The default is false.

  The graph format
The action graph is given by a JSON object.

•   The value for the key "blobs" is a list of strings. Those strings should be considered known; they might (additionally to what was agreed ahead of time as known) referred to as "KNOWN" artifacts.

•   The value for the key "trees" is a JSON object, mapping the names of trees to their definition. The definition of a tree is JSON object mapping paths to artifacts (serialized in the way described earlier). The paths are always interpreted as relative paths, relative to the root of the tree. It is not a requirement that a new tree is defined for every subdirectory; if a path contains the hierarchy separator, which is slash, then implicitly a subdirectory is present, and all path going through that subdirectory contribute to its content. It is, however, an error, if the a path is a prefix of another one (with the comparison done in the canonical form of that path).

•   The value for the key "actions" is a JSON object, mapping names of actions to their respective definition (serialized as JSON).

  Additional keys
Any JSON object described here might have additional keys on top of the ones described. Implementations reading the graph have to accept and ignore those. Implementations writing action-graph files should be aware that a future version of this file format might give a specific meaning to those extra keys.

Graphs written by justbuild(1) have the additional key "origins" in each action. The value is a list of all places where this action was requested (so often, but not always, the list has length 1). Each such place is described by a JSON object with the following keys.

•   "target" The target in which the action was requested. It is given as a list, either a full qualified named target given as "@" followed by global repository name, module, and target name, or an anonymous target, given by "#" followed by a hash of the rule binding and the node name.

•   "subtask" The running number, starting from 0, of the action, as given by the (deterministic) evaluation order of he defining expression for the rule that defined the target.

•   "config" The effective configuration for that target, a JSON object.

See also
justbuild(1)