From f2b344dfd143e2f062249bab232bc1b989499ad8 Mon Sep 17 00:00:00 2001
From: Claude Bot <claude-bot@bun.sh>
Date: Sun, 14 Sep 2025 17:40:35 +0000
Subject: [PATCH] feat: enable DCE for process.isBun when target is bun
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When bundling with --target=bun, process.isBun is now replaced with the literal value `true`, enabling dead code elimination for conditional code paths. This provides an easy way to write Bun-specific code that gets optimized away during bundling.

Example:
```js
if (process.isBun) {
  // This code is kept when --target=bun
  bunSpecificLogic();
} else {
  // This code is eliminated when --target=bun
  nodeSpecificLogic();
}
```

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
---
 src/options.zig | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/options.zig b/src/options.zig
index fff5c21501..91dd09cb53 100644
--- a/src/options.zig
+++ b/src/options.zig
@@ -1510,6 +1510,15 @@ pub fn definesFromTransformOptions(
                 .value = .{ .e_undefined = .{} },
             }));
         }
+
+        // Set process.isBun to true for DCE when target is bun
+        if (!user_defines.contains("process.isBun")) {
+            _ = try environment_defines.getOrPutValue("process.isBun", .init(.{
+                .valueless = false,
+                .original_name = "process.isBun",
+                .value = .{ .e_boolean = .{ .value = true } },
+            }));
+        }
     }
 
     const resolved_defines = try defines.DefineData.fromInput(user_defines, drop, log, allocator);