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45 lines
1.6 KiB
JavaScript
45 lines
1.6 KiB
JavaScript
"use strict";
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const unreachable = require("@joepie91/unreachable");
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const assert = require("assert");
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const splitFilter = require("split-filter");
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const _nixTypes = require("./util/nix-types");
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function isValidBodyAttribute(binding) {
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assert(binding.attrpath.type === "NixAttributePath");
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assert(binding.attrpath.attr.length > 0);
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assert(binding.attrpath.attr[0].type === "NixAttributeIdentifier");
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if (binding.attrpath.attr[0].name === "body") {
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if (binding.attrpath.attr.length > 1) {
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throw unreachable("attribute paths should have been desugared");
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} else {
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return true;
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}
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} else {
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return false;
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}
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}
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module.exports = {
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name: "desugar-let-attribute-set",
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visitors: {
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NixLetAttributeSet: (node) => {
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// We save a bunch of complexity here by directly translating to a recursive attribute set instead of `let..in`; our JS representation of `let..in` is *functionally* identical to how a LetAttributeSet works. We just use a different attribute name to represent the returned evaluation.
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let [ bodyBindings, actualBindings ] = splitFilter(node.bind, (binding) => isValidBodyAttribute(binding));
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if (bodyBindings.length === 0) {
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// TODO: Display source code position + snippet
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// FIXME: It's possible to specify the `body` with a dynamic key; this means that we can't actually do a compile-time check here, at least not reliably, and we need to insert a runtime guard if the compile-time check fails and dynamic attributes are specified
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throw new Error(`Missing required 'body' attribute in LetAttributeSet`);
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} else {
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return _nixTypes.JSNixLet(
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actualBindings,
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bodyBindings[0].expression
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);
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}
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}
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}
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};
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