@coat/cli/build/util/get-location-in-json-ast.js

TODO: See #3

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.getLocationInJSONAst = getLocationInJSONAst;
var _types = require("@babel/types");
/**
 * Adjusts a source location to correctly display the
 * helper characters for @babel/codeframe in a JSON AST.
 *
 * @param location The source location property of the AST or node
 * @returns The adjusted source location
 */
function shiftLocation(location) {
  const singleLine = location.start.line === location.end.line;
  return {
    start: {
      ...location.start,
      column: location.start.column + 1
    },
    end: {
      ...location.end,
      column: singleLine ? location.end.column + 1 : location.end.column
    }
  };
}

/**
 * Returns the source location of a property path inside a JSON AST.
 *
 * @param ast The JSON AST parsed by @babel/parser
 * @param path The property path within the JSON object
 * @returns The source location
 */
function getLocationInJSONAst(ast, path) {
  const [head, ...tail] = path;
  if (typeof head === "undefined") {
    // The property path is empty, which means that the location
    // should describe the whole JSON value
    //
    if (!ast.loc) {
      throw new Error("AST does not have loc information.");
    }
    return shiftLocation(ast.loc);
  } else if (typeof head === "string") {
    if (!(0, _types.isObjectExpression)(ast)) {
      throw new Error(`Expected ast root node to be ObjectExpression for current path: ${path.join(".")}`);
    }

    // Find the desired property within the AST
    const desiredProperty = ast.properties.filter(prop => (0, _types.isObjectProperty)(prop))
    // Reverse the AST to prefer property declarations that follow later,
    // since JSON properties can be written multiple times and the
    // most recent declaration overwrites previous ones.
    .reverse().find(prop =>
    // Typical JSON string literal, e.g.:
    // { "a": 1 }
    (0, _types.isStringLiteral)(prop.key) && prop.key.value === head ||
    // JSON5 non-string identifier, e.g.:
    // { a: 1 }
    (0, _types.isIdentifier)(prop.key) && prop.key.name);
    if (!desiredProperty) {
      throw new Error(`Could not find property for current path: ${path.join(".")}`);
    }
    if (tail.length) {
      return getLocationInJSONAst(desiredProperty.value, tail);
    }
    if (!desiredProperty.loc) {
      throw new Error(`Property does not have loc information for current path: ${path.join(".")}`);
    }
    return shiftLocation(desiredProperty.loc);
  }
  if (!(0, _types.isArrayExpression)(ast)) {
    throw new Error(`Expected ast root node to be ArrayExpression for current path: ${path.join(".")}`);
  }
  const element = ast.elements[head];
  if (!element) {
    throw new Error(`Array element is not defined for current path: ${path.join(".")}`);
  }
  if (tail.length) {
    return getLocationInJSONAst(element, tail);
  }
  if (!element.loc) {
    throw new Error(`Element does not have loc information for current path: ${path.join(".")}`);
  }
  return shiftLocation(element.loc);
}