WIP, identifier mangling, inherit support

src/mangle-name.js

@@ -0,0 +1,42 @@
+"use strict";
+
+const assert = require("assert");
+
+const acceptableFirstCharacters = /^[a-zA-Z_]$/;
+const acceptableSubsequentCharacters = /^[0-9a-zA-Z_]$/;
+
+// This function deterministically and statelessly translates a name such that it is guaranteed to be valid in all identifier positions in JS.
+// TODO: This can probably be made more performant...
+
+function mangleCharacter(character) {
+	return (character === "$")
+		? "$$"
+		: `$${character.codePointAt(0)}`
+}
+
+module.exports = function mangleName(name) {
+	assert(name.length > 0);
+	
+	// FIXME: Tag an identifier of this type with an internal property instead
+	if (name.startsWith("$$jsNix$")) {
+		return name;
+	} else {
+		let completedFirstCharacter = false;
+
+		return Array.from(name)
+			.map((character) => {
+				if (!completedFirstCharacter) {
+					completedFirstCharacter = true;
+					
+					return (acceptableFirstCharacters.test(character))
+						? character
+						: mangleCharacter(character);
+				} else {
+					return (acceptableSubsequentCharacters.test(character))
+						? character
+						: mangleCharacter(character);
+				}
+			})
+			.join("");
+	}
+};

src/prepare-ast.js

@@ -95,6 +95,15 @@ function convertNode(node) {
 		result.recursive = false;
 	}
 
+	if (type === "inherit") {
+		// We're inheriting from scope here, so the source expression is explicitly not set
+		result.expression = null;
+	} else if (type === "inherit_from") {
+		// Already set
+	}
+
+	// console.log(result);
+
 	result.type = matchValue(result.type, {
 		source_expression: "NixProgram",
 		token: "NixAnonymousToken",
@@ -112,6 +121,10 @@ function convertNode(node) {
 		identifier: "NixIdentifier",
 		attr_identifier: "NixAttributeIdentifier",
 		attrpath: "NixAttributePath",
+		inherit: "NixInherit",
+		inherit_from: "NixInherit",
+		attrs_inherited: "NixInheritAttributes",
+		attrs_inherited_from: "NixInheritAttributes",
 		bind: "NixBinding",
 		binary: "NixBinaryOperation",
 		app: "NixFunctionCall",

src/transformers/_nix-types.js

@@ -28,13 +28,22 @@ let types = module.exports = {
 		};
 	},
 	NixAttributePath: function (attributes) {
+		// NOTE: This does not accept an array of strings! Instead, specify as an array of NixAttributeIdentifiers
+		// TODO: Add proper validation for this
 		assert(Array.isArray(attributes));
+		assert(!attributes.some((attribute) => typeof attribute === "string"));
 	
 		return {
 			type: "NixAttributePath",
 			attr: attributes
 		};
 	},
+	NixIdentifier: function (name) {
+		return {
+			type: "NixIdentifier",
+			name: name
+		};
+	},
 	NixAttributeIdentifier: function (name) {
 		return {
 			type: "NixAttributeIdentifier",
@@ -47,5 +56,12 @@ let types = module.exports = {
 			attrpath: types.NixAttributePath(attributePath),
 			expression: expression
 		};
+	},
+	NixLetIn: function (bindings, body) {
+		return {
+			type: "NixLetIn",
+			bind: bindings,
+			body: body
+		};
 	}
 };

src/transformers/attribute-sets.js

@@ -3,10 +3,14 @@
 const assert = require("assert");
 const types = require("@babel/types");
 const template = require("@babel/template").default;
+const splitFilter = require("split-filter");
+
 const unpackExpression = require("./_unpack-expression");
 const NoChange = require("../astformer/actions/no-change");
 const printAst = require("../print-ast");
 
+// 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
+
 // FIXME: Add expression parens!
 let tmplCallLazy = template(`
 	%%wrapper%%()
@@ -81,9 +85,10 @@ module.exports = {
 
 			return defer((node) => {
 				let isRecursive = node.recursive;
-				let hasDynamicBindings = node.bind.some((binding) => isDynamicBinding(binding));
 
-				let bindings = node.bind.map((binding) => {
+				let [ dynamicNodes, staticNodes ] = splitFilter(node.bind, (binding) => isDynamicBinding(binding));
+
+				let staticBindings = staticNodes.map((binding) => {
 					assert(binding.attrpath.attr.length === 1); // Nested attributes should have been desugared by this point
 
 					return {
@@ -92,17 +97,18 @@ module.exports = {
 					};
 				});
 
-				if (hasDynamicBindings) {
+				if (dynamicNodes.length > 0) {
+					printAst(node);
 					throw new Error(`UNIMPLEMENTED: Dynamic bindings are not supported yet`); 
 				} else if (isRecursive) {
 					return unpackExpression(tmplScopeWrapper({
-						bindings: bindings.map(({ name, expression }) => {
+						bindings: staticBindings.map(({ name, expression }) => {
 							return tmplRecursiveBinding({
 								name: name,
 								expression: expression
 							});
 						}),
-						object: types.objectExpression(bindings.map(({ name }) => {
+						object: types.objectExpression(staticBindings.map(({ name }) => {
 							return types.objectProperty(
 								types.stringLiteral(name),
 								types.identifier(name)
@@ -110,7 +116,7 @@ module.exports = {
 						}))
 					}));
 				} else {
-					let object = types.objectExpression(bindings.map(({ name, expression }) => {
+					let object = types.objectExpression(staticBindings.map(({ name, expression }) => {
 						return types.objectProperty(
 							types.stringLiteral(name),
 							// TODO: Remove the isRecursive distinction here once heap-of-vars works

src/transformers/desugar-attrsets.js

@@ -1,6 +1,7 @@
 "use strict";
 
 
+const unreachable = require("@joepie91/unreachable")("jsNix");
 const NoChange = require("../astformer/actions/no-change");
 
 const { NixAttributeIdentifier, NixAttributeSet, NixBinding } = require("./_nix-types");
@@ -44,39 +45,42 @@ module.exports = {
 			let dynamicBindings = [];
 
 			for (let binding of node.bind) {
-				if (binding.attrpath.attr.length > 1) {
-					neededDesugaring = true;
-				}
-
-				let firstAttribute = binding.attrpath.attr[0];
-				let isStaticAttribute = firstAttribute.type === "NixAttributeIdentifier";
-
-				if (isStaticAttribute) {
-					let attributeName = firstAttribute.name;
-					let existingBinding = newStaticBindings[attributeName];
-
-					if (existingBinding == null) {
-						newStaticBindings[attributeName] = NixBinding(
-							[ firstAttribute ],
-							unpackBindingValue(binding)
-						);
-					} else {
-						if (isAttributeSet(existingBinding.expression) && isAttributeSet(binding.expression)) {
-							neededDesugaring = true;
-
-							newStaticBindings[attributeName] = mergeBindings(attributeName, existingBinding, binding);
+				if (binding.type === "NixBinding") {
+					if (binding.attrpath.attr.length > 1) {
+						neededDesugaring = true;
+					}
+					
+					let firstAttribute = binding.attrpath.attr[0];
+					let isStaticAttribute = firstAttribute.type === "NixAttributeIdentifier";
+
+					if (isStaticAttribute) {
+						let attributeName = firstAttribute.name;
+						let existingBinding = newStaticBindings[attributeName];
+
+						if (existingBinding == null) {
+							newStaticBindings[attributeName] = NixBinding(
+								[ firstAttribute ],
+								unpackBindingValue(binding)
+							);
 						} else {
-							throw new Error(`Key '${attributeName}' was specified twice, but this is only allowed when both values are an attribute set`);
+							if (isAttributeSet(existingBinding.expression) && isAttributeSet(binding.expression)) {
+								neededDesugaring = true;
+
+								newStaticBindings[attributeName] = mergeBindings(attributeName, existingBinding, binding);
+							} else {
+								throw new Error(`Key '${attributeName}' was specified twice, but this is only allowed when both values are an attribute set`);
+							}
 						}
+					} else {
+						// FIXME: Needs runtime check, need to *always* construct objects at runtime when dynamic bindings are involved
+						dynamicBindings.push(binding);
 					}
 				} else {
-					// FIXME: Needs runtime check, need to *always* construct objects at runtime when dynamic bindings are involved
-					dynamicBindings.push(binding);
+					unreachable(`unrecognized binding type: ${binding.type}`);
 				}
 			}
 
 			let staticBindingList = Object.entries(newStaticBindings).map(([ key, value ]) => {
-				// console.log([ key, value ]);
 				return value;
 			});
 

src/transformers/desugar-inherits.js

@@ -0,0 +1,62 @@
+"use strict";
+
+const splitFilter = require("split-filter");
+const assert = require("assert");
+
+const NoChange = require("../astformer/actions/no-change");
+const nixTypes = require("./_nix-types");
+
+module.exports = {
+	name: "desugar-inherits",
+	visitors: {
+		NixAttributeSet: (node) => {
+			let [ inherits, regularBindings ] = splitFilter(node.bind, (binding) => binding.type === "NixInherit");
+
+			if (inherits.length === 0) {
+				return NoChange;
+			} else {
+				let tempCounter = 0;
+				let inherits_ = inherits.map((inherit) => {
+					return {
+						tempName: `$$jsNix$temp$${tempCounter++}`,
+						sourceExpression: inherit.expression,
+						names: inherit.attrs.attr.map((attribute) => {
+							assert(attribute.type === "NixAttributeIdentifier");
+							return attribute.name;
+						})
+					};
+				});
+
+				let letBindings = inherits_.map((inherit) => {
+					return nixTypes.NixBinding(
+						[ nixTypes.NixAttributeIdentifier(inherit.tempName) ],
+						inherit.sourceExpression
+					);
+				});
+
+				let body = {
+					... node,
+					bind: [
+						... regularBindings,
+						... inherits_.flatMap((inherit) => {
+							return inherit.names.map((name) => {
+								return nixTypes.NixBinding(
+									[ nixTypes.NixAttributeIdentifier(name) ],
+									nixTypes.NixAttributeSelection(
+										nixTypes.NixIdentifier(inherit.tempName),
+										[ nixTypes.NixAttributeIdentifier(name) ]
+									)
+								);
+							});
+						})
+					]
+				};
+
+				return nixTypes.NixLetIn(
+					letBindings,
+					body
+				);
+			}
+		}
+	}
+};

src/transformers/functions.js

@@ -6,7 +6,6 @@ const types = require("@babel/types");
 const template = require("@babel/template").default;
 const unpackExpression = require("./_unpack-expression");
 
-// TODO: Memoize every function
 // NOTE: These are arrow functions because variable references within functions should always refer to the nearest scope; and since we use `this` to handle variable references within recursive attribute sets, we need to ensure that a function definition *does not* create its own `this` context.
 let tmplFunctionDefinitionFormalsUniversal = template(`
 	((%%universal%%) => {

src/transformers/index.js

@@ -91,6 +91,8 @@ let trivial = {
 };
 
 module.exports = [
+	require("./desugar-inherits"),
+	require("./mangle-identifiers"),
 	require("./let-in"),
 	require("./desugar-attrsets"),
 	require("./literals"),

src/transformers/mangle-identifiers.js

@@ -0,0 +1,24 @@
+"use strict";
+
+const NoChange = require("../astformer/actions/no-change");
+const mangleName = require("../mangle-name");
+
+function mangleNode(node) {
+	if (node._isMangled) {
+		return NoChange;
+	} else {
+		return {
+			... node,
+			name: mangleName(node.name),
+			_isMangled: true
+		};
+	}
+}
+
+module.exports = {
+	name: "mangle-identifiers",
+	visitors: {
+		NixAttributeIdentifier: mangleNode,
+		NixIdentifier: mangleNode
+	}
+};