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116 lines
3.6 KiB
JavaScript
116 lines
3.6 KiB
JavaScript
"use strict";
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const assert = require("assert");
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const types = require("@babel/types");
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const template = require("@babel/template").default;
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const splitFilter = require("split-filter");
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const unpackExpression = require("./util/unpack-expression");
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const NoChange = require("../astformer/actions/no-change");
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const printAst = require("../print-ast");
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const lazyWrapper = require("./templates/lazy-wrapper");
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const callLazyWrapper = require("./templates/call-lazy-wrapper");
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// TODO: Optimize lazy evaluation wrappers by only unpacking them selectively when used in an actual expression; in particular, that avoids the "wrapper that just calls another wrapper" overhead when passing attributes as function arguments
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let tmplExtend = template(`(
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$$jsNix$extend(this ?? {}, %%object%%)
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)`);
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let tmplScopeWrapper = template(`(
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(() => {
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%%bindings%%;
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return %%object%%;
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})()
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)`);
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// FIXME: Verify that this always works, and that we don't need `var` for hoisting!
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let tmplRecursiveBinding = template(`
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const %%name%% = %%expression%%;
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`);
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function isDynamicBinding(binding) {
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return binding.attrpath.attr[0].type !== "NixAttributeIdentifier";
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}
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module.exports = {
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name: "attribute-sets",
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visitors: {
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Program: (_node, { setContext }) => {
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setContext(null, "attributeSets_inRecursiveSet", false);
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return NoChange;
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},
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NixAttributeSelection: (_node, { defer }) => {
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// TODO: Optimize dynamic attribute access by translating builtins.getAttr to dynamic property access at compile time? This requires scope analysis!
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return defer((node) => {
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assert(node.attrpath.type === "NixAttributePath");
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return node.attrpath.attr.reduce((last, identifier) => {
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assert(identifier.type === "NixAttributeIdentifier");
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return callLazyWrapper(types.memberExpression(last, types.identifier(identifier.name)));
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}, node.expression);
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});
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},
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NixAttributeSet: (node, { defer, setContext, getContext }) => {
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if (node.recursive) {
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setContext(null, "attributeSets_inRecursiveSet", true);
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}
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return defer((node) => {
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let isRecursive = node.recursive;
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let [ dynamicNodes, staticNodes ] = splitFilter(node.bind, (binding) => isDynamicBinding(binding));
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let staticBindings = staticNodes.map((binding) => {
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assert(binding.attrpath.attr.length === 1); // Nested attributes should have been desugared by this point
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return {
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name: binding.attrpath.attr[0].name,
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expression: lazyWrapper(binding.expression)
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};
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});
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if (dynamicNodes.length > 0) {
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printAst(node);
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throw new Error(`UNIMPLEMENTED: Dynamic bindings are not supported yet`);
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} else if (isRecursive) {
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return unpackExpression(tmplScopeWrapper({
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bindings: staticBindings.map(({ name, expression }) => {
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return tmplRecursiveBinding({
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name: name,
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expression: expression
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});
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}),
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object: types.objectExpression(staticBindings.map(({ name }) => {
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return types.objectProperty(
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types.stringLiteral(name),
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types.identifier(name)
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);
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}))
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}));
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} else {
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let object = types.objectExpression(staticBindings.map(({ name, expression }) => {
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return types.objectProperty(
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types.stringLiteral(name),
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// TODO: Remove the isRecursive distinction here once heap-of-vars works
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expression
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);
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}));
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// Only do prototypal inheritance for `this` if we're dealing with nested recursive attribute sets
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if (isRecursive && getContext("attributeSets_inRecursiveSet") === true) {
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return unpackExpression(tmplExtend({
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object: object
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}));
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} else {
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return object;
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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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