chore: asserts that all comments are printed

packages/babel-generator/src/index.ts

@@ -24,9 +24,12 @@ class Generator extends Printer {
     const map = opts.sourceMaps ? new SourceMap(opts, code) : null;
     super(format, map);
 
+    this.opts = opts;
     this.ast = ast;
   }
 
+  opts: GeneratorOptions;
+
   ast: t.Node;
 
   /**
@@ -36,7 +39,30 @@ class Generator extends Printer {
    */
 
   generate() {
-    return super.generate(this.ast);
+    const code = super.generate(this.ast);
+
+    const comments = (this.ast as { comments?: t.Comment[] }).comments;
+    if (comments?.length) {
+      let num = 0;
+      let last;
+      for (const v of comments) {
+        if (!this._printedComments.has(v) && !v.ignore) {
+          last = v;
+          num++;
+        }
+      }
+      if (num > 0) {
+        console.error(
+          `[@babel/generator] Error: There are ${num} comments that were not printed normally, please open an issue on babel repo.\nThe last is \`${
+            last.value
+          }\` at ${
+            this.opts.filename || this.opts.sourceFileName || "unknown file"
+          }:${last.loc?.start.line}:${last.loc?.start.column}`,
+        );
+      }
+    }
+
+    return code;
   }
 }
 

packages/babel-generator/src/printer.ts

@@ -908,10 +908,10 @@ class Printer {
       return true;
     }
 
-    if (!this.format.shouldPrintComment(comment.value)) return false;
-
     this._printedComments.add(comment);
 
+    if (!this.format.shouldPrintComment(comment.value)) return false;
+
     const isBlockComment = comment.type === "CommentBlock";
 
     // Add a newline before and after a block comment, unless explicitly