js_printer: wrap cross-module enum inlined as a delete operand when non-finite

src/js_printer/lib.rs

@@ -1242,6 +1242,7 @@ pub enum ExprFlag {
     HasNonOptionalChainParent,
     ExprResultIsUnused,
     IsFollowedByOf,
+    IsDeleteTarget,
 }
 
 pub(crate) type ExprFlagSet = enumset::EnumSet<ExprFlag>;
@@ -3255,6 +3256,7 @@ pub(crate) mod __gated_printer {
                 }
                 ExprData::EDot(e) => {
                     let is_optional_chain = e.optional_chain == Some(js_ast::OptionalChain::Start);
+                    let is_delete_target = flags.contains(ExprFlag::IsDeleteTarget);
 
                     let mut wrap = false;
                     if e.optional_chain.is_none() {
@@ -3264,7 +3266,7 @@ pub(crate) mod __gated_printer {
                         if let Some(inlined) =
                             self.try_to_get_imported_enum_value(e.target, &e.name)
                         {
-                            self.print_inlined_enum(inlined, &e.name, level);
+                            self.print_inlined_enum(inlined, &e.name, level, is_delete_target);
                             return;
                         }
                     } else {
@@ -3306,6 +3308,9 @@ pub(crate) mod __gated_printer {
                     }
                 }
                 ExprData::EIndex(e) => {
+                    let is_delete_target = flags.contains(ExprFlag::IsDeleteTarget);
+                    flags.remove(ExprFlag::IsDeleteTarget);
+
                     let mut wrap = false;
                     if e.optional_chain.is_none() {
                         flags.insert(ExprFlag::HasNonOptionalChainParent);
@@ -3316,7 +3321,12 @@ pub(crate) mod __gated_printer {
                                 if let Some(value) =
                                     self.try_to_get_imported_enum_value(e.target, str.slice8())
                                 {
-                                    self.print_inlined_enum(value, str.slice8(), level);
+                                    self.print_inlined_enum(
+                                        value,
+                                        str.slice8(),
+                                        level,
+                                        is_delete_target,
+                                    );
                                     return;
                                 }
                             }
@@ -4008,7 +4018,17 @@ pub(crate) mod __gated_printer {
                         self.print_expr(e.value, Level::Prefix.sub(1), ExprFlag::none());
                         self.print(b")");
                     } else {
-                        self.print_expr(e.value, Level::Prefix.sub(1), ExprFlag::none());
+                        let mut value_flags = ExprFlag::none();
+                        if e.op == Op::Code::UnDelete
+                            && e.flags.contains(
+                                E::UnaryFlags::WAS_ORIGINALLY_DELETE_OF_IDENTIFIER_OR_PROPERTY_ACCESS,
+                            )
+                        {
+                            // Gate on the parse-time flag so this never reaches compound
+                            // operands (EIf/EBinary) that forward `flags` to non-target children.
+                            value_flags.insert(ExprFlag::IsDeleteTarget);
+                        }
+                        self.print_expr(e.value, Level::Prefix.sub(1), value_flags);
                     }
                     }
 
@@ -6159,7 +6179,20 @@ pub(crate) mod __gated_printer {
             inlined: js_ast::InlinedEnumValueDecoded,
             comment: &[u8],
             level: Level,
+            is_delete_target: bool,
         ) {
+            // `delete NaN` / `delete Infinity` is a strict-mode SyntaxError; wrap so the
+            // inlined value stays a value, not a Reference.
+            let wrap = is_delete_target
+                && matches!(inlined, js_ast::InlinedEnumValueDecoded::Number(n) if !n.is_finite());
+            let level = if wrap {
+                self.print(b"(0,");
+                self.print_space();
+                Level::Comma
+            } else {
+                level
+            };
+
             match inlined {
                 js_ast::InlinedEnumValueDecoded::Number(num) => self.print_number(num, level),
                 // TODO: extract printString
@@ -6185,6 +6218,10 @@ pub(crate) mod __gated_printer {
                     self.print(b" */");
                 }
             }
+
+            if wrap {
+                self.print(b")");
+            }
         }
 
         pub(crate) fn print_decl_stmt(

test/bundler/esbuild/ts.test.ts

@@ -2236,6 +2236,69 @@ describe("bundler", () => {
       ]);
     },
   });
+  // Cross-module enum inlining happens at print time after
+  // WAS_ORIGINALLY_DELETE_OF_IDENTIFIER_OR_PROPERTY_ACCESS has already bypassed the
+  // `(0, ...)` re-wrap in the EUnary print arm. When the inlined value prints as `NaN`
+  // or `Infinity` that yields `delete NaN`, a strict-mode SyntaxError in the ESM bundle.
+  // Finite numbers and strings are fine (`delete 42` / `delete "s"` are valid and true).
+  itBundled("ts/EnumCrossModuleInliningDeleteTarget", {
+    files: {
+      "/entry.ts": /* ts */ `
+        import { E } from './enums'
+        console.log(JSON.stringify([
+          delete E.N,
+          delete E.I,
+          delete E.NI,
+          delete E.F,
+          delete E.S,
+          delete E["N"],
+          delete E["I"],
+        ]))
+      `,
+      "/enums.ts": /* ts */ `
+        export enum E {
+          N = 0 / 0,
+          I = 1 / 0,
+          NI = -1 / 0,
+          F = 42,
+          S = "s",
+        }
+      `,
+    },
+    minifySyntax: false, // intentionally disabled. enum inlining always happens
+    run: { stdout: "[true,true,true,true,true,true,true]" },
+    onAfterBundle(api) {
+      const out = api.readFile("/out.js");
+      // The bundle is an ES module: `delete NaN` / `delete Infinity` would be a
+      // SyntaxError. Non-finite values must be wrapped; finite/string values need not be.
+      expect(out).not.toContain("delete NaN");
+      expect(out).not.toContain("delete Infinity");
+      expect(out).toContain("delete (0, NaN /* N */)");
+      expect(out).toContain("delete (0, Infinity /* I */)");
+      expect(out).toContain("delete (0, -Infinity /* NI */)");
+      expect(out).toContain("delete 42 /* F */");
+      expect(out).toContain('delete "s" /* S */');
+    },
+  });
+  itBundled("ts/EnumCrossModuleInliningDeleteTargetMinified", {
+    files: {
+      "/entry.ts": /* ts */ `
+        import { E } from './enums'
+        console.log(JSON.stringify([delete E.N, delete E.I, delete E["N"]]))
+      `,
+      "/enums.ts": /* ts */ `
+        export enum E { N = 0 / 0, I = 1 / 0 }
+      `,
+    },
+    minifyWhitespace: true,
+    minifySyntax: true,
+    run: { stdout: "[true,true,true]" },
+    onAfterBundle(api) {
+      const out = api.readFile("/out.js");
+      expect(out).not.toContain("delete NaN");
+      expect(out).toContain("delete(0,NaN)");
+    },
+  });
   itBundled("ts/EnumExportClause", {
     files: {
       "/entry.ts": /* ts */ `