Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for pushed-based package distribution. In one aspect, a method combines accepting a plurality of persistent connections in which each connection is initiated by a different client, determining a version of a package for each of the clients, and distributing the package version to the clients.

Abstract: A matching library of a code analysis system defines a number of predicates applicable to an abstract syntax tree (AST) corresponding to program code being analyzed. The predicates represent whether or not nodes of the program code's AST have corresponding properties, such as representing a class that inherits from another given class. The code analysis system obtains an AST to analyze, a predicate expression query that includes predicates of the matching library, and action code. The code analysis system identifies nodes of the AST that match the predicate expression query by executing code of the matching library and executes the action code against the identified nodes.

Abstract: A build system and method, including receiving attribute rules and new rules, wherein the attribute rules correspond to one or more predefined default actions of the build system, wherein the new rules specify new actions that are to be added to the build system. A graph is generated to include files specified as attributes in the attributes rules and the one or more predefined default actions that correspond to the attributes rules. A request to enable at least one of the new rules is received. Action listener rules are received, wherein the action listener rules indicate default actions and corresponding new rules of the one or more new rules. The graph is checked for default actions that are indicated in the action listener rules. Additional actions are added to the graph for new rules based on the default actions indicated in the action listener rules.