chore(bundler): more tests

tools/src/main/js/bundler/test/README.md

@@ -14,29 +14,51 @@ Minimal snapshot test for `../cli.js`. No test framework required — plain Node
 └── snapshot/         # expected bundler output, committed
     ├── main-bundled.schema.json      # pretty bundle, all `$comment` kept
     ├── main-bundled.min.schema.json  # minified bundle, only the root `$comment` kept
-    └── report.json                   # bundler report (embedded / external / rewired / warnings)
+    └── report.json                   # bundler report (embedded / external / rewired / tree-shake / warnings)
 ```
 
 The runner copies `fixtures/` to a temporary directory, runs the CLI's `main()` there with
 `main.schema.json` as the entry and `modules/` as the modules directory, writes the returned
 report to `report.json`, and compares all three generated files byte-for-byte against `snapshot/`.
 
-Each module file name states the edge case it covers (`used-whole`, `used-subdefs-only`,
-`used-properties-only`, `unused`, `dynamic-anchor`); `externals/not-bundled` covers a file outside
+Each module file name states the edge case it covers; `externals/not-bundled` covers a file outside
 the modules directory, the `remote` property in `used-whole` covers an absolute `https://` ref, and
 `inArray` in `used-whole` covers refs nested inside an array (`allOf`).
 
+The modules exercise the tree-shaker as follows:
+
+- `used-whole` — referenced as a whole from the entry; the module body survives untouched, but
+  its unreferenced `$defs/unusedButKept` is dropped nevertheless.
+- `used-subdefs-only` — only individual `$defs` are referenced; the module body (`type`, `properties`)
+  is dropped, the module is hollowed, and `$defs/dropped` is removed. A ref from the dropped body
+  to `unused` must *not* make `unused` reachable.
+- `used-properties-only` — only nested *properties* are referenced, via JSON pointers like
+  `#/properties/address/properties/geo/properties/lat`. Only the referenced property subtrees
+  (and what they transitively reach, i.e. `$defs/degrees`) are kept; the containers along the path
+  (`address`, `geo`, the module itself) are hollowed; unreferenced siblings (`city`, `lon`,
+  `unusedTopLevel`) and `$defs/unusedDef` are dropped.
+- `used-array-items` — refs point *into* schema arrays (`#/properties/combined/allOf/1`,
+  `#/properties/choice/oneOf/1`) and to a *non-schema* value (`#/properties/status/enum`).
+  Non-reached array siblings (`allOf/0`, `allOf/2`, `oneOf/0`) must be replaced by a void
+  `{"not": …}` placeholder — never removed, so indices and pointers stay stable, and never
+  serialised as `null`. The non-schema target is kept as a whole and its parent `status` is
+  hollowed. `$defs/keptViaArray` is kept transitively via `allOf/1`; `$defs/droppedDef` is removed.
+  A ref from the void `allOf/2` to `unused` must *not* make `unused` reachable.
+- `unused` — nothing reachable refers to it; the whole module is removed.
+- `dynamic-anchor` — declares a `$dynamicAnchor`; the tree-shaker cannot follow anchors and keeps it as is.
+
 The entry schema additionally covers:
 
 - a property *named* `$comment` (`properties.$comment`) — it must survive minification,
   only its own `$comment` keyword is stripped;
 - local refs into the entry's own `$defs` — they are rewired to the hollow container
-  `#/$defs/main/$defs/…`, which is marked with `"not": {"$comment": …}`.
+  `#/$defs/main/$defs/…`, which is marked with `"not": {"$comment": …}`; the unreferenced
+  `$defs/mainUnused` is dropped from that container.
 - an inline object property (`properties.composed`) whose own properties reference
-  *properties* of a module rather than its `$defs` — via JSON pointers like
-  `#/properties/address/properties/geo/properties/lat`. Only the referenced property subtrees
-  (and what they transitively reach) of `used-properties-only` are kept; unreferenced siblings
-  (`city`, `lon`, `unusedTopLevel`), unreachable `$defs` and `unused.schema.json` are dropped.
+  *properties* of a module rather than its `$defs` (see `used-properties-only` above).
+- refs into *array items* and to a *non-schema value* of a module
+  (`properties.middle`, `properties.lastChoice`, `properties.statusValues`;
+  see `used-array-items` above).
 
 Inside the fixtures, the annotation keywords have distinct roles:
 
@@ -49,8 +71,9 @@ Inside the fixtures, the annotation keywords have distinct roles:
 
 `report.json` pins the bundler's bookkeeping: which files were embedded and under which
 `$defs` key, which refs were left external, every rewired ref (source → target), the
-tree-shake result, and the validation warnings. Paths in the report are relative to the
-entry schema's directory, so the snapshot is independent of the temporary work directory.
+tree-shake result (every `reached`, `hollowed` and `removed` JSON pointer), and the
+validation warnings. Paths in the report are relative to the entry schema's directory,
+so the snapshot is independent of the temporary work directory.
 
 ## Run
 

tools/src/main/js/bundler/test/fixtures/main.schema.json

@@ -54,6 +54,24 @@
           "$ref": "modules/used-properties-only.schema.json#/properties/contact"
         }
       }
+    },
+    "middle": {
+      "$comment": "Ref INTO a schema array (allOf/1) of a module -> siblings allOf/0 and allOf/2 must become void placeholders, not null; the index must stay 1.",
+      "title": "Middle",
+      "description": "The middle part of the module's combined schema.",
+      "$ref": "modules/used-array-items.schema.json#/properties/combined/allOf/1"
+    },
+    "lastChoice": {
+      "$comment": "Ref INTO the last item of a oneOf -> the preceding item must become a void placeholder.",
+      "title": "Last choice",
+      "description": "The last alternative of the module's choice.",
+      "$ref": "modules/used-array-items.schema.json#/properties/choice/oneOf/1"
+    },
+    "statusValues": {
+      "$comment": "Ref to a NON-schema value (the module's enum array). Semantically dubious, but a legal pointer -> the tree-shaker must record it as reached (no crash) and keep the enum intact.",
+      "title": "Status values",
+      "description": "Pointer to the module's status enum.",
+      "$ref": "modules/used-array-items.schema.json#/properties/status/enum"
     }
   },
   "$defs": {

tools/src/main/js/bundler/test/fixtures/modules/used-array-items.schema.json

@@ -0,0 +1,92 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "http://example.com/test/modules/used-array-items.schema.json",
+  "$comment": "FIXTURE: refs point INTO schema arrays and to NON-schema values of this module. The module itself is never referenced as a whole -> hollowed.",
+  "title": "Used array items",
+  "description": "A module of which only individual array items and a non-schema value are referenced.",
+  "type": "object",
+  "properties": {
+    "combined": {
+      "$comment": "Only allOf/1 is referenced from main. allOf/0 and allOf/2 are not reached -> they must become void placeholders, never JSON null, so that the index of allOf/1 stays stable. 'combined' itself is not reached -> hollowed.",
+      "title": "Combined",
+      "description": "A composition of which only the middle part is referenced.",
+      "allOf": [
+        {
+          "$comment": "allOf/0: NOT referenced -> void placeholder.",
+          "title": "Combined part 0",
+          "description": "The first part.",
+          "type": "object",
+          "properties": {
+            "a": {
+              "title": "A",
+              "description": "An unreferenced value.",
+              "type": "string"
+            }
+          }
+        },
+        {
+          "$comment": "allOf/1: referenced from main via #/properties/combined/allOf/1 -> kept as a whole, including its internal ref to $defs/keptViaArray.",
+          "title": "Combined part 1",
+          "description": "The middle part.",
+          "type": "object",
+          "properties": {
+            "b": {
+              "title": "B",
+              "description": "A value defined in this module.",
+              "$ref": "#/$defs/keptViaArray"
+            }
+          }
+        },
+        {
+          "$comment": "allOf/2: NOT referenced -> void placeholder. Its ref must NOT make unused.schema.json reachable.",
+          "title": "Combined part 2",
+          "description": "The last part.",
+          "$ref": "unused.schema.json"
+        }
+      ]
+    },
+    "choice": {
+      "$comment": "Only the LAST item of oneOf is referenced -> oneOf/0 becomes a void placeholder, oneOf/1 is kept.",
+      "title": "Choice",
+      "description": "A choice of which only the last alternative is referenced.",
+      "oneOf": [
+        {
+          "$comment": "oneOf/0: NOT referenced -> void placeholder.",
+          "title": "Choice 0",
+          "description": "The first alternative.",
+          "type": "null"
+        },
+        {
+          "$comment": "oneOf/1: referenced from main via #/properties/choice/oneOf/1.",
+          "title": "Choice 1",
+          "description": "The second alternative.",
+          "type": "integer"
+        }
+      ]
+    },
+    "status": {
+      "$comment": "A NON-schema value of this schema (the enum array) is referenced from main via #/properties/status/enum. The enum must be kept as a whole; 'status' itself is not reached -> hollowed; its 'type' is dropped.",
+      "title": "Status",
+      "description": "A status value.",
+      "type": "string",
+      "enum": [
+        "on",
+        "off"
+      ]
+    }
+  },
+  "$defs": {
+    "keptViaArray": {
+      "$comment": "Only reachable via combined.allOf/1.",
+      "title": "Kept via array",
+      "description": "A boolean value.",
+      "type": "boolean"
+    },
+    "droppedDef": {
+      "$comment": "Not reachable -> shaken away.",
+      "title": "Dropped def",
+      "description": "A definition nothing reachable refers to.",
+      "type": "null"
+    }
+  }
+}