[@kbn/handlebars] Improve print_ast.js script (#147086)

packages/kbn-handlebars/README.md

@@ -129,48 +129,15 @@ Output:
       },
       params: [],
       hash: undefined,
-      escaped: true,
-      strip: { open: false, close: false }
-    }
-  ],
-  strip: {}
-}
-```
-
-You can also filter which properties not to display, e.g:
-
-```sh
-./packages/kbn-handlebars/scripts/print_ast.js '{{#myBlock}}Hello {{name}}{{/myBlock}}' params,hash,loc,strip,data,depth,parts,inverse,openStrip,inverseStrip,closeStrip,blockParams,escaped
-```
-
-Output:
-
-```js
-{
-  type: 'Program',
-  body: [
-    {
-      type: 'BlockStatement',
-      path: { type: 'PathExpression', original: 'myBlock' },
-      program: {
-        type: 'Program',
-        body: [
-          {
-            type: 'ContentStatement',
-            original: 'Hello ',
-            value: 'Hello '
-          },
-          {
-            type: 'MustacheStatement',
-            path: { type: 'PathExpression', original: 'name' }
-          }
-        ]
-      }
+      escaped: true
     }
   ]
 }
 ```
 
+By default certain properties will be hidden in the output.
+For more control over the output, check out the options by running the script without any arguments.
+
 ### Print generated code
 
 It's possible to see the generated JavaScript code that `handlebars` create for a given template using the following command line tool:

packages/kbn-handlebars/scripts/print_ast.js

@@ -5,20 +5,31 @@
  */
 'use strict'; // eslint-disable-line strict
 
+const { relative } = require('path');
 const { inspect } = require('util');
 
 const { parse } = require('handlebars');
+const argv = require('minimist')(process.argv.slice(2));
 
-const template = process.argv[2];
-const filter = (process.argv[3] || 'loc').split(',');
-const containsSubNodes = ['body', 'path', 'program', 'params'];
+const DEFAULT_FILTER = 'loc,strip,openStrip,inverseStrip,closeStrip';
+
+const filter = argv['show-all'] ? [''] : (argv.filter || DEFAULT_FILTER).split(',');
+const hideEmpty = argv['hide-empty'] || false;
+const template = argv._[0];
 
 if (template === undefined) {
-  console.log(`Usage: ${process.argv[1]} <template> <filter>`);
+  const script = relative(process.cwd(), process.argv[1]);
+  console.log(`Usage: ${script} [options] <template>`);
+  console.log();
+  console.log('Options:');
+  console.log('  --filter=...  A comma separated list of keys to filter from the output.');
+  console.log(`                Default: ${DEFAULT_FILTER}`);
+  console.log('  --hide-empty  Do not display empty properties.');
+  console.log('  --show-all    Do not filter out any properties. Equivalent to --filter="".');
+  console.log();
+  console.log('Example:');
+  console.log(`  ${script} --hide-empty -- 'hello {{name}}'`);
   console.log();
-  console.log(
-    'By default, <filter> will be "loc", but can be set to any comma separated list of keys to filter from the output'
-  );
   process.exit(1);
 }
 
@@ -34,9 +45,17 @@ function reduce(ast) {
       delete ast[k];
     }
 
-    for (const k of containsSubNodes) {
-      if (k in ast) {
-        ast[k] = reduce(ast[k]);
+    if (hideEmpty) {
+      for (const [k, v] of Object.entries(ast)) {
+        if (v === undefined || v === null || (Array.isArray(v) && v.length === 0)) {
+          delete ast[k];
+        }
+      }
+    }
+
+    for (const [k, v] of Object.entries(ast)) {
+      if (typeof v === 'object' && v !== null) {
+        ast[k] = reduce(v);
       }
     }
   }