128 lines
5.3 KiB
Python
128 lines
5.3 KiB
Python
"""Generics support via go_generics.
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A Go template is similar to a go library, except that it has certain types that
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can be replaced before usage. For example, one could define a templatized List
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struct, whose elements are of type T, then instantiate that template for
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T=segment, where "segment" is the concrete type.
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"""
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TemplateInfo = provider(
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"Information about a go_generics template.",
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fields = {
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"unsafe": "whether the template requires unsafe code",
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"types": "required types",
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"opt_types": "optional types",
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"consts": "required consts",
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"opt_consts": "optional consts",
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"deps": "package dependencies",
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"template": "merged template source file",
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},
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)
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def _go_template_impl(ctx):
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srcs = ctx.files.srcs
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template = ctx.actions.declare_file(ctx.label.name + "_template.go")
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args = ["-o=%s" % template.path] + [f.path for f in srcs]
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ctx.actions.run(
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inputs = srcs,
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outputs = [template],
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mnemonic = "GoGenericsTemplate",
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progress_message = "Building Go template %s" % ctx.label,
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arguments = args,
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executable = ctx.executable._tool,
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)
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return [TemplateInfo(
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types = ctx.attr.types,
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opt_types = ctx.attr.opt_types,
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consts = ctx.attr.consts,
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opt_consts = ctx.attr.opt_consts,
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deps = ctx.attr.deps,
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template = template,
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)]
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go_template = rule(
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implementation = _go_template_impl,
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attrs = {
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"srcs": attr.label_list(doc = "the list of source files that comprise the template", mandatory = True, allow_files = True),
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"deps": attr.label_list(doc = "the standard dependency list", allow_files = True, cfg = "target"),
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"types": attr.string_list(doc = "the list of generic types in the template that are required to be specified"),
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"opt_types": attr.string_list(doc = "the list of generic types in the template that can but aren't required to be specified"),
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"consts": attr.string_list(doc = "the list of constants in the template that are required to be specified"),
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"opt_consts": attr.string_list(doc = "the list of constants in the template that can but aren't required to be specified"),
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"_tool": attr.label(executable = True, cfg = "host", default = Label("//tools/go_generics/go_merge")),
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},
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)
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def _go_template_instance_impl(ctx):
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info = ctx.attr.template[TemplateInfo]
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output = ctx.outputs.out
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# Check that all required types are defined.
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for t in info.types:
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if t not in ctx.attr.types:
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fail("Missing value for type %s in %s" % (t, ctx.attr.template.label))
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# Check that all defined types are expected by the template.
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for t in ctx.attr.types:
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if (t not in info.types) and (t not in info.opt_types):
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fail("Type %s is not a parameter to %s" % (t, ctx.attr.template.label))
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# Check that all required consts are defined.
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for t in info.consts:
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if t not in ctx.attr.consts:
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fail("Missing value for constant %s in %s" % (t, ctx.attr.template.label))
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# Check that all defined consts are expected by the template.
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for t in ctx.attr.consts:
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if (t not in info.consts) and (t not in info.opt_consts):
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fail("Const %s is not a parameter to %s" % (t, ctx.attr.template.label))
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# Build the argument list.
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args = ["-i=%s" % info.template.path, "-o=%s" % output.path]
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if ctx.attr.package:
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args.append("-p=%s" % ctx.attr.package)
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if len(ctx.attr.prefix) > 0:
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args.append("-prefix=%s" % ctx.attr.prefix)
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if len(ctx.attr.suffix) > 0:
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args.append("-suffix=%s" % ctx.attr.suffix)
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args += [("-t=%s=%s" % (p[0], p[1])) for p in ctx.attr.types.items()]
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args += [("-c=%s=%s" % (p[0], p[1])) for p in ctx.attr.consts.items()]
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args += [("-import=%s=%s" % (p[0], p[1])) for p in ctx.attr.imports.items()]
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if ctx.attr.anon:
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args.append("-anon")
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ctx.actions.run(
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inputs = [info.template],
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outputs = [output],
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mnemonic = "GoGenericsInstance",
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progress_message = "Building Go template instance %s" % ctx.label,
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arguments = args,
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executable = ctx.executable._tool,
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)
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return [DefaultInfo(
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files = depset([output]),
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)]
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go_template_instance = rule(
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implementation = _go_template_instance_impl,
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attrs = {
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"template": attr.label(doc = "the label of the template to be instantiated", mandatory = True),
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"prefix": attr.string(doc = "a prefix to be added to globals in the template"),
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"suffix": attr.string(doc = "a suffix to be added to globals in the template"),
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"types": attr.string_dict(doc = "the map from generic type names to concrete ones"),
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"consts": attr.string_dict(doc = "the map from constant names to their values"),
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"imports": attr.string_dict(doc = "the map from imports used in types/consts to their import paths"),
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"anon": attr.bool(doc = "whether anoymous fields should be processed", mandatory = False, default = False),
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"package": attr.string(doc = "the package for the generated source file", mandatory = False),
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"out": attr.output(doc = "output file", mandatory = True),
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"_tool": attr.label(executable = True, cfg = "host", default = Label("//tools/go_generics")),
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},
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)
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