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105 lines
3.2 KiB
JavaScript
105 lines
3.2 KiB
JavaScript
"use strict";
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const unreachable = require("@joepie91/unreachable")("jsNix");
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const NoChange = require("../astformer/actions/no-change");
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const { NixAttributeIdentifier, NixAttributeSet, NixBinding } = require("./util/nix-types");
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function isAttributeSet(node) {
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return (node.type === "NixAttributeSet");
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}
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function mergeAttributeSets(a, b) {
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return NixAttributeSet([ ... a.bind, ... b.bind ]);
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}
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function mergeBindings(name, a, b) {
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let attributes = mergeAttributeSets(unpackBindingValue(a), unpackBindingValue(b));
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return NixBinding(
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[ NixAttributeIdentifier(name) ],
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attributes
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);
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}
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function unpackBindingValue(binding) {
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// binding -> value for top-level attribute of the binding
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if (binding.attrpath.attr.length > 1) {
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// Nested attribute path syntax, synthesize a new attribute set with the first attribute snipped off - this new attribute set represents the *value* of the binding
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return NixAttributeSet([
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NixBinding(binding.attrpath.attr.slice(1), binding.expression)
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]);
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} else {
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return binding.expression;
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}
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}
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/* FIXME: Cases to test/verify:
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{ a = 4; a.b = 5; }
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{ a = {}; a.b = 5; }
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{ a.c = 4; a.b = 5; }
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{ a = 4; a = 5; }
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*/
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module.exports = {
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name: "desugar-attrsets",
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visitors: {
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NixAttributeSet: (node) => {
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let neededDesugaring = false;
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let newStaticBindings = {};
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let dynamicBindings = [];
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for (let binding of node.bind) {
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if (binding.type === "NixBinding") {
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if (binding.attrpath.attr.length > 1) {
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neededDesugaring = true;
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}
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let firstAttribute = binding.attrpath.attr[0];
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let isStaticAttribute = firstAttribute.type === "NixAttributeIdentifier";
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if (isStaticAttribute) {
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let attributeName = firstAttribute.name;
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let existingBinding = newStaticBindings[attributeName];
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if (existingBinding == null) {
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newStaticBindings[attributeName] = NixBinding(
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[ firstAttribute ],
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unpackBindingValue(binding)
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);
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} else {
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if (isAttributeSet(existingBinding.expression) && isAttributeSet(binding.expression)) {
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neededDesugaring = true;
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newStaticBindings[attributeName] = mergeBindings(attributeName, existingBinding, binding);
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} else {
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throw new Error(`Key '${attributeName}' was specified twice, but this is only allowed when both values are an attribute set`);
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}
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}
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} else {
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// FIXME: Needs runtime check, need to *always* construct objects at runtime when dynamic bindings are involved
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// FIXME: Still just desugar here? And expect another transformer to deal with the runtime checks
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// desugar but do not merge, dynamic bindings cannot be combined with attribute paths on the same key
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dynamicBindings.push(binding);
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}
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} else {
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unreachable(`unrecognized binding type: ${binding.type}`);
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}
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}
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let staticBindingList = Object.entries(newStaticBindings).map(([ _key, value ]) => {
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return value;
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});
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// We only check this here because there are multiple things that could cause a need for desugaring, and this is simpler for now than having a separate 'check first' implementation
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if (neededDesugaring) {
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return NixAttributeSet([ ... staticBindingList, ... dynamicBindings ], node.recursive);
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} else {
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return NoChange;
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}
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}
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}
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};
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