diff --git a/kube/prototext.libsonnet b/kube/prototext.libsonnet new file mode 100644 index 00000000..419a511c --- /dev/null +++ b/kube/prototext.libsonnet @@ -0,0 +1,76 @@ +// An untyped prototext marshaller. Like std.manifestJson, but when you want to +// emit proto-but-not-really. +// +// This supports recursively nested objects/arrays with string, number and bool +// leaves. All hidden object fields are ignored. The given value must be an +// object. +// +// One unintuitive aspect of proto(text) is that you cannot have +// multidimensional arrays, ie. the following is forbidden: +// +// manifestProtoText({foo: [[1, 2]]}) +// +// RUNTIME ERROR: manifestProtoText: at .foo[0]: double nested arrays are +// unsupported by prototext + +{ + local top = self, + + // manifestProtoText takes an object and returns a serialized prototext + // representation of it. If indentation is "", then a single-line prototext + // will be emitted, otherwise a multi-line prototext will be emitted with + // each object depth being indented by the indentation value. + manifestProtoText:: function(value, indentation=" ") top.recurse(value, indentation, 0, [""]), + + // Available as std.repeat in jsonnet 0.15 + repeat:: function(str, count) if count <= 0 then "" else (str + top.repeat(str, count-1)), + + emit:: function(str, indentation, nindent) ( + top.repeat(indentation, nindent) + str + (if indentation == "" then " " else "\n") + ), + + fatal:: function(str, path) error "manifestProtoText: at %s: %s" % [std.join("", path), str], + + // objectField emits a rendered `k: v` object field, potentially recursing + // back into recurse for printing the value of object. The value must not + // be an array, these are handled/flattened by recurse. + objectField:: function(name, value, indentation, nindent, path) ( + if std.isObject(value) then ( + top.emit("%s <" % [name], indentation, nindent) + + top.recurse(value, indentation, nindent+1, path) + + top.emit(">", indentation, nindent) + ) else if std.isArray(value) then ( + top.fatal("double nested arrays are unsupported by prototext", path) + ) else if std.isFunction(value) then ( + top.fatal("cannot manifest functions", path) + ) else if std.isBoolean(value) then ( + top.emit("%s: %s" % [name, if value then "true" else "false"], indentation, nindent) + ) else if std.isNumber(value) then ( + top.emit("%s: %s" % [name, std.toString(value)], indentation, nindent) + ) else if std.isString(value) then ( + // Atempt to properly escape strings via JSON manifestation. Not + // entirely sure this always works. + top.emit("%s: %s" % [name, std.manifestJson(value)], indentation, nindent) + ) else ( + top.fatal("unknown type %s" % [std.type(value)], path) + ) + ), + + // recurse returns the string representation of an object as prototext. + recurse:: function(value, indentation, nindent, path) ( + if std.isObject(value) then std.join("", [ + ( + local field = value[fieldName]; + if std.isArray(field) then std.join("", std.mapWithIndex(function(i, el) ( + local newPath = path + ["."+fieldName, "[%d]" % [i]]; + top.objectField(fieldName, el, indentation, nindent, newPath) + ), field)) else ( + local newPath = path + ["."+fieldName]; + top.objectField(fieldName, field, indentation, nindent, newPath) + ) + ) + for fieldName in std.objectFields(value) + ]) else + top.fatal("manifestProtoText can only manifest objects", path) + ), +}