def _go_template_impl(ctx): input = ctx.files.srcs output = ctx.outputs.out args = ["-o=%s" % output.path] + [f.path for f in input] ctx.actions.run( inputs = input, outputs = [output], mnemonic = "GoGenericsTemplate", progress_message = "Building Go template %s" % ctx.label, arguments = args, executable = ctx.executable._tool, ) return struct( types = ctx.attr.types, opt_types = ctx.attr.opt_types, consts = ctx.attr.consts, opt_consts = ctx.attr.opt_consts, deps = ctx.attr.deps, file = output, ) """ Generates a Go template from a set of Go files. A Go template is similar to a go library, except that it has certain types that can be replaced before usage. For example, one could define a templatized List struct, whose elements are of type T, then instantiate that template for T=segment, where "segment" is the concrete type. Args: name: the name of the template. srcs: the list of source files that comprise the template. types: the list of generic types in the template that are required to be specified. opt_types: the list of generic types in the template that can but aren't required to be specified. consts: the list of constants in the template that are required to be specified. opt_consts: the list of constants in the template that can but aren't required to be specified. deps: the list of dependencies. """ go_template = rule( attrs = { "srcs": attr.label_list( mandatory = True, allow_files = True, ), "deps": attr.label_list(allow_files = True), "types": attr.string_list(), "opt_types": attr.string_list(), "consts": attr.string_list(), "opt_consts": attr.string_list(), "_tool": attr.label( executable = True, cfg = "host", default = Label("//tools/go_generics:go_merge"), ), }, outputs = { "out": "%{name}_template.go", }, implementation = _go_template_impl, ) def _go_template_instance_impl(ctx): template = ctx.attr.template output = ctx.outputs.out # Check that all required types are defined. for t in template.types: if t not in ctx.attr.types: fail("Missing value for type %s in %s" % (t, ctx.attr.template.label)) # Check that all defined types are expected by the template. for t in ctx.attr.types: if (t not in template.types) and (t not in template.opt_types): fail("Type %s it not a parameter to %s" % (t, ctx.attr.template.label)) # Check that all required consts are defined. for t in template.consts: if t not in ctx.attr.consts: fail("Missing value for constant %s in %s" % (t, ctx.attr.template.label)) # Check that all defined consts are expected by the template. for t in ctx.attr.consts: if (t not in template.consts) and (t not in template.opt_consts): fail("Const %s it not a parameter to %s" % (t, ctx.attr.template.label)) # Build the argument list. args = ["-i=%s" % template.file.path, "-o=%s" % output.path] args += ["-p=%s" % ctx.attr.package] if len(ctx.attr.prefix) > 0: args += ["-prefix=%s" % ctx.attr.prefix] if len(ctx.attr.suffix) > 0: args += ["-suffix=%s" % ctx.attr.suffix] args += [("-t=%s=%s" % (p[0], p[1])) for p in ctx.attr.types.items()] args += [("-c=%s=%s" % (p[0], p[1])) for p in ctx.attr.consts.items()] args += [("-import=%s=%s" % (p[0], p[1])) for p in ctx.attr.imports.items()] ctx.actions.run( inputs = [template.file], outputs = [output], mnemonic = "GoGenericsInstance", progress_message = "Building Go template instance %s" % ctx.label, arguments = args, executable = ctx.executable._tool, ) # TODO: How can we get the dependencies out? return struct( files = depset([output]) ) """ Instantiates a Go template by replacing all generic types with concrete ones. Args: name: the name of the template instance. template: the label of the template to be instatiated. prefix: a prefix to be added to globals in the template. suffix: a suffix to be added to global in the template. types: the map from generic type names to concrete ones. consts: the map from constant names to their values. imports: the map from imports used in types/consts to their import paths. package: the name of the package the instantiated template will be compiled into. """ go_template_instance = rule( attrs = { "template": attr.label( mandatory = True, providers = ["types"], ), "prefix": attr.string(), "suffix": attr.string(), "types": attr.string_dict(), "consts": attr.string_dict(), "imports": attr.string_dict(), "package": attr.string(mandatory = True), "out": attr.output(mandatory = True), "_tool": attr.label( executable = True, cfg = "host", default = Label("//tools/go_generics"), ), }, implementation = _go_template_instance_impl, )