Fixes #188 #3345

src/Template.js

@@ -637,8 +637,77 @@ class Template extends TemplateContent {
  });
  }
 
+ static async runPreprocessors(inputPath, content, data, preprocessors) {
+ let skippedVia = false;
+ for (let [name, preprocessor] of Object.entries(preprocessors)) {
+ let { filter, callback } = preprocessor;
+
+ let filters;
+ if (Array.isArray(filter)) {
+ filters = filter;
+ } else if (typeof filter === "string") {
+ filters = filter.split(",");
+ } else {
+ throw new Error(
+ `Expected file extensions passed to "${name}" content preprocessor to be a string or array. Received: ${filter}`,
+ );
+ }
+
+ if (!filters.some((extension) => extension === "*" || inputPath.endsWith(extension))) {
+ // skip
+ continue;
+ }
+
+ try {
+ let ret = await callback.call(
+ {
+ inputPath,
+ },
+ data,
+ content,
+ );
+
+ // Returning explicit false is the same as ignoring the template
+ if (ret === false) {
+ skippedVia = name;
+ continue;
+ }
+
+ // Different from transforms: returning falsy (not false) here does nothing (skips the preprocessor)
+ if (ret) {
+ content = ret;
+ }
+ } catch (e) {
+ throw new EleventyBaseError(
+ `Preprocessor \`${name}\` encountered an error when transforming ${inputPath}.`,
+ e,
+ );
+ }
+ }
+
+ return {
+ skippedVia,
+ content,
+ };
+ }
+
  async getTemplates(data) {
- let rawInput = await this.getPreRender();
+ let content = await this.getPreRender();
+ let { skippedVia, content: rawInput } = await Template.runPreprocessors(
+ this.inputPath,
+ content,
+ data,
+ this.config.preprocessors,
+ );
+
+ if (skippedVia) {
+ debug(
+ "Skipping %o, the %o preprocessor returned an explicit `false`",
+ this.inputPath,
+ skippedVia,
+ );
+ return [];
+ }
 
  // https://github.com/11ty/eleventy/issues/1206
  data.page.rawInput = rawInput;

src/TemplateConfig.js

@@ -333,6 +333,8 @@ class TemplateConfig {
  }
 
  this.userConfig.activeNamespace = storedActiveNamespace;
+
+ this.userConfig._disablePluginExecution();
  }
 
  /**

src/UserConfig.js

@@ -102,6 +102,8 @@ class UserConfig {
 
  this.linters = {};
  this.transforms = {};
+ this.preprocessors = {};
+
  this.activeNamespace = "";
  this.DateTime = DateTime;
  this.dynamicPermalinks = true;
@@ -544,6 +546,11 @@ class UserConfig {
  this.#pluginExecution = true;
  }
 
+ // Internal method
+ _disablePluginExecution() {
+ this.#pluginExecution = false;
+ }
+
  /* Config is executed in two stages and plugins are the second stage—are we in the plugins stage? */
  isPluginExecution() {
  return this.#pluginExecution;
@@ -999,6 +1006,15 @@ class UserConfig {
  this.transforms[name] = this.#decorateCallback(`"${name}" Transform`, callback);
  }
 
+ addPreprocessor(name, fileExtensions, callback) {
+ name = this.getNamespacedName(name);
+
+ this.preprocessors[name] = {
+ filter: fileExtensions,
+ callback: this.#decorateCallback(`"${name}" Preprocessor`, callback),
+ };
+ }
+
  addLinter(name, callback) {
  name = this.getNamespacedName(name);
 
@@ -1055,6 +1071,7 @@ class UserConfig {
  // filters removed in 1.0 (use addTransform instead)
  transforms: this.transforms,
  linters: this.linters,
+ preprocessors: this.preprocessors,
  globalData: this.globalData,
  layoutAliases: this.layoutAliases,
  layoutResolution: this.layoutResolution,

test/EleventyTest.js

@@ -1527,3 +1527,23 @@ test("#1419: Shortcode in a permalink", async (t) => {
  t.is(results.length, 1);
  t.is(results[0].url, `/url-slug/`);
 });
+
+test("#188: Content preprocessing", async (t) => {
+ let elev = new Eleventy("./test/stubs-virtual/", undefined, {
+ config: eleventyConfig => {
+ eleventyConfig.addPreprocessor("drafts", ".njk", (data, content) => {
+ if(data.draft) {
+ return false;
+ }
+ return `Hello ${content}`;
+ });
+
+ eleventyConfig.addTemplate("index.njk", "Before");
+ eleventyConfig.addTemplate("draft.njk", "Before", { draft: true });
+ }
+ });
+
+ let results = await elev.toJSON();
+ t.is(results.length, 1);
+ t.is(results[0].content, `Hello Before`);
+});