Handling undefined/null values in context object for string templates, replacing with empty string.

packages/string-templates/package.json

@@ -12,15 +12,16 @@
     "test": "jest"
   },
   "dependencies": {
-    "handlebars": "^4.7.6"
+    "handlebars": "^4.7.6",
+    "lodash": "^4.17.20"
   },
   "devDependencies": {
+    "jest": "^26.6.3",
     "rollup": "^2.36.2",
     "rollup-plugin-commonjs": "^10.1.0",
     "rollup-plugin-node-builtins": "^2.1.2",
     "rollup-plugin-node-globals": "^1.4.0",
     "rollup-plugin-node-resolve": "^5.2.0",
-    "typescript": "^4.1.3",
-    "jest": "^26.6.3"
+    "typescript": "^4.1.3"
   }
 }

packages/string-templates/src/custom/postprocessor.js

@@ -0,0 +1,6 @@
+class Postprocessor {
+  constructor(name, fn) {
+    this.name = name
+    this.fn = fn
+  }
+}

packages/string-templates/src/custom/preprocessor.js

@@ -6,6 +6,12 @@ const {
   includesAny,
 } = require("../utilities")
 
+const PreprocessorNames = {
+  SWAP_TO_DOT: "swap-to-dot-notation",
+  HANDLE_SPACES: "handle-spaces-in-properties",
+  FINALISE: "finalise",
+}
+
 class Preprocessor {
   constructor(name, fn) {
     this.name = name
@@ -20,7 +26,7 @@ class Preprocessor {
 }
 
 const PROCESSORS = [
-  new Preprocessor("swap-to-dot-notation", statement => {
+  new Preprocessor(PreprocessorNames.SWAP_TO_DOT, statement => {
     let startBraceIdx = statement.indexOf("[")
     let lastIdx = 0
     while (startBraceIdx !== -1) {
@@ -34,7 +40,7 @@ const PROCESSORS = [
     return statement
   }),
 
-  new Preprocessor("handle-spaces-in-properties", statement => {
+  new Preprocessor(PreprocessorNames.HANDLE_SPACES, statement => {
     // exclude helpers and brackets, regex will only find double brackets
     const exclusions = HelperFunctions.concat(["{{", "}}"])
     // find all the parts split by spaces
@@ -62,7 +68,7 @@ const PROCESSORS = [
     return statement.replace(/\[\[/g, "[").replace(/]]/g, "]")
   }),
 
-  new Preprocessor("finalise", statement => {
+  new Preprocessor(Preprocessor.FINALISE, statement => {
     let insideStatement = statement.slice(2, statement.length - 2)
     if (insideStatement.charAt(0) === " ") {
       insideStatement = insideStatement.slice(1)
@@ -74,7 +80,7 @@ const PROCESSORS = [
       insideStatement = `(${insideStatement})`
     }
     return `{{ all ${insideStatement} }}`
-  })
+  }),
 ]
 
 /**

packages/string-templates/src/helpers/index.js

@@ -27,6 +27,10 @@ const HELPERS = [
   }),
   // this help is applied to all statements
   new Helper(HelperFunctionNames.ALL, value => {
+    // null/undefined values produce bad results
+    if (value == null) {
+      return ""
+    }
     let text = new SafeString(unescape(value).replace(/&/g, "&"))
     if (text == null || typeof text !== "string") {
       return text

packages/string-templates/src/index.js

@@ -1,6 +1,8 @@
 const handlebars = require("handlebars")
 const { registerAll } = require("./helpers/index")
 const { preprocess } = require("./custom/preprocessor")
+const { cloneDeep } = require("lodash/fp")
+const { removeNull } = require("./utilities")
 
 const hbsInstance = handlebars.create()
 registerAll(hbsInstance)
@@ -78,6 +80,8 @@ module.exports.processObjectSync = (object, context) => {
  * @returns {string} The enriched string, all templates should have been replaced if they can be.
  */
 module.exports.processStringSync = (string, context) => {
+  const clonedContext = removeNull(cloneDeep(context))
+  // remove any null/undefined properties
   if (typeof string !== "string") {
     throw "Cannot process non-string types."
   }
@@ -85,7 +89,7 @@ module.exports.processStringSync = (string, context) => {
   string = preprocess(string)
   // this does not throw an error when template can't be fulfilled, have to try correct beforehand
   template = hbsInstance.compile(string)
-  return template(context)
+  return template(clonedContext)
 }
 
 /**

packages/string-templates/src/utilities.js

@@ -13,3 +13,15 @@ module.exports.swapStrings = (string, start, length, swap) => {
 module.exports.includesAny = (string, options) => {
   return options.some(option => string.includes(option))
 }
+
+// removes null and undefined
+module.exports.removeNull = obj => {
+  return Object.fromEntries(
+    Object.entries(obj)
+      .filter(([key, value]) => value != null)
+      .map(([key, value]) => [
+        key,
+        value === Object(value) ? module.exports.removeNull(value) : value,
+      ])
+  )
+}

packages/string-templates/test/basic.spec.js

@@ -27,6 +27,14 @@ describe("Test that the string processing works correctly", () => {
     }
     expect(error).not.toBeNull()
   })
+
+  it("confirm that null properties are handled correctly", async () => {
+    const output = await processString("hello {{ name }} I am {{ name2 }}", {
+      name: undefined,
+      name2: null,
+    })
+    expect(output).toBe("hello  I am ")
+  })
 })
 
 describe("Test that the object processing works correctly", () => {

packages/string-templates/yarn.lock

@@ -2799,7 +2799,7 @@ lodash.sortby@^4.7.0:
   resolved "https://registry.yarnpkg.com/lodash.sortby/-/lodash.sortby-4.7.0.tgz#edd14c824e2cc9c1e0b0a1b42bb5210516a42438"
   integrity sha1-7dFMgk4sycHgsKG0K7UhBRakJDg=
 
-lodash@^4.17.19:
+lodash@^4.17.19, lodash@^4.17.20:
   version "4.17.20"
   resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.20.tgz#b44a9b6297bcb698f1c51a3545a2b3b368d59c52"
   integrity sha512-PlhdFcillOINfeV7Ni6oF1TAEayyZBoZ8bcshTHqOYJYlrqzRK5hagpagky5o4HfCzzd1TRkXPMFq6cKk9rGmA==