From 946d2fca24a1b8e71004d9c08c0626f18f184701 Mon Sep 17 00:00:00 2001
From: Ben Surgison <ben.surgison@digital.cabinet-office.gov.uk>
Date: Wed, 22 Nov 2023 18:16:23 +0000
Subject: [PATCH] Add filters and functions when the environment is ready

---
 CHANGELOG.md                |  4 ++++
 lib/filters/api.js          |  3 ++-
 lib/filters/core-filters.js | 10 ++++++----
 lib/functions/api.js        |  3 ++-
 lib/utils/index.js          | 14 ++++++++++----
 5 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 95db7b62e5..89ebdd48a2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Fixes
+
+- [#2378: Add filters and functions when the environment is ready](https://github.com/alphagov/govuk-prototype-kit/pull/2378)
+
 ## 13.15.1
 
 ### Fixes
diff --git a/lib/filters/api.js b/lib/filters/api.js
index 3c4f93e073..1475d291d9 100644
--- a/lib/filters/api.js
+++ b/lib/filters/api.js
@@ -55,5 +55,6 @@ module.exports = {
     addFilter,
     getFilter
   },
-  setEnvironment
+  setEnvironment,
+  runWhenEnvIsAvailable
 }
diff --git a/lib/filters/core-filters.js b/lib/filters/core-filters.js
index e7618b91b6..f96df7720c 100644
--- a/lib/filters/core-filters.js
+++ b/lib/filters/core-filters.js
@@ -1,7 +1,6 @@
 // local dependencies
-const { addFilter, getFilter } = require('../../').views
-
-const nunjucksSafe = getFilter('safe')
+const { runWhenEnvIsAvailable, external } = require('./api')
+const { addFilter, getFilter } = external
 
 /**
  * Logs an object in the template to the console in the browser.
@@ -10,4 +9,7 @@ const nunjucksSafe = getFilter('safe')
  * @example {{ "hello world" | log }}
  * @example {{ "hello world" | log | safe }}  [for environments with autoescaping turned on]
  */
-addFilter('log', a => nunjucksSafe('<script>console.log(' + JSON.stringify(a, null, '\t') + ');</script>'))
+runWhenEnvIsAvailable(() => {
+  const nunjucksSafe = getFilter('safe')
+  addFilter('log', a => nunjucksSafe('<script>console.log(' + JSON.stringify(a, null, '\t') + ');</script>'))
+})
diff --git a/lib/functions/api.js b/lib/functions/api.js
index e38e1f6a24..73059d5793 100644
--- a/lib/functions/api.js
+++ b/lib/functions/api.js
@@ -62,5 +62,6 @@ module.exports = {
     addFunction,
     getFunction
   },
-  setEnvironment
+  setEnvironment,
+  runWhenEnvIsAvailable
 }
diff --git a/lib/utils/index.js b/lib/utils/index.js
index 9320e54d9f..353b3bea58 100644
--- a/lib/utils/index.js
+++ b/lib/utils/index.js
@@ -18,6 +18,8 @@ const plugins = require('../plugins/plugins')
 const routes = require('../routes/api')
 const { appDir, projectDir } = require('./paths')
 const { asyncSeriesMap } = require('./asyncSeriesMap')
+const { runWhenEnvIsAvailable: runWhenFiltersEnvIsAvailable } = require('../filters/api')
+const { runWhenEnvIsAvailable: runWhenFunctionsEnvIsAvailable } = require('../functions/api')
 
 // Tweak the Markdown renderer
 const defaultMarkedRenderer = marked.defaults.renderer || new marked.Renderer()
@@ -53,8 +55,10 @@ function addNunjucksFilters (env) {
   if (fs.existsSync(filtersPath)) {
     additionalFilters.push(filtersPath)
   }
-  const filterFiles = plugins.getFileSystemPaths('nunjucksFilters').concat(additionalFilters)
-  filterFiles.forEach(x => require(x))
+  runWhenFiltersEnvIsAvailable(() => {
+    const filterFiles = plugins.getFileSystemPaths('nunjucksFilters').concat(additionalFilters)
+    filterFiles.forEach(x => require(x))
+  })
 }
 
 // Require core and custom functions, merges to one object
@@ -66,8 +70,10 @@ function addNunjucksFunctions (env) {
   if (fs.existsSync(functionsPath)) {
     additionalFunctions.push(functionsPath)
   }
-  const globalFiles = plugins.getFileSystemPaths('nunjucksFunctions').concat(additionalFunctions)
-  globalFiles.forEach(x => require(x))
+  runWhenFunctionsEnvIsAvailable(() => {
+    const globalFiles = plugins.getFileSystemPaths('nunjucksFunctions').concat(additionalFunctions)
+    globalFiles.forEach(x => require(x))
+  })
 }
 
 function addRouters (app) {