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80 lines
2.4 KiB
JavaScript
80 lines
2.4 KiB
JavaScript
"use strict";
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const splitFilter = require("split-filter");
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const assert = require("assert");
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const NoChange = require("../astformer/actions/no-change");
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const nixTypes = require("./util/nix-types");
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module.exports = {
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name: "desugar-inherits",
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visitors: {
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NixAttributeSet: (node) => {
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let [ inherits, regularBindings ] = splitFilter(node.bind, (binding) => binding.type === "NixInherit");
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if (inherits.length === 0) {
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return NoChange;
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} else {
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let tempCounter = 0;
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let inherits_ = inherits.map((inherit) => {
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return {
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tempName: `$temp$${tempCounter++}`,
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sourceExpression: inherit.expression,
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names: inherit.attrs.attr.map((attribute) => {
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assert(attribute.type === "NixAttributeIdentifier");
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return attribute.name;
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})
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};
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});
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let letBindings = inherits_.map((inherit) => {
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return nixTypes.NixBinding(
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[ nixTypes.NixAttributeIdentifier(inherit.tempName) ],
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inherit.sourceExpression
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);
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});
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let inheritedAttributeBindings = inherits_.flatMap((inherit) => {
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return inherit.names.map((name) => {
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return nixTypes.NixBinding(
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[ nixTypes.NixAttributeIdentifier(name) ],
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nixTypes.NixAttributeSelection(
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nixTypes.NixIdentifier(inherit.tempName),
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[ nixTypes.NixAttributeIdentifier(name) ]
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)
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);
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});
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});
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if (node.recursive === false) {
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// When not recursive, we need to ensure that the temporary variables are defined a scope *higher* than the attribute set that actually makes use of their properties, because we cannot access those variables from the attribute bindings otherwise.
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return nixTypes.NixLetIn(
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letBindings,
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{
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... node,
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bind: [
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... regularBindings,
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... inheritedAttributeBindings
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]
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}
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);
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} else {
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// ... but when recursive, we *must* specify the temporary variables as part of the recursive attribute set itself, because otherwise we don't have the ability to bidirectionally reference between fixed attributes and inherited ones; see, for example, eval-okay-scope-7.nix.
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// FIXME: Mark the temporary variables as 'internal' so that they don't get returned in the final object; this would make the generated code more readable.
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return {
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... node,
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bind: [
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... regularBindings,
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... letBindings,
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... inheritedAttributeBindings
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]
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};
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}
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}
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}
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}
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};
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