From 897b4fb8aba1ff4b77be88043f6192f01ed6a19c Mon Sep 17 00:00:00 2001
From: Pat Hickey <pat@moreproductive.org>
Date: Fri, 29 Jan 2021 15:48:55 -0800
Subject: [PATCH] wasictxbuilder: assert that stdio is provided

---
 crates/wasi-common/src/ctx.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/crates/wasi-common/src/ctx.rs b/crates/wasi-common/src/ctx.rs
index 5f3c798fa1..20a9ef7064 100644
--- a/crates/wasi-common/src/ctx.rs
+++ b/crates/wasi-common/src/ctx.rs
@@ -64,6 +64,17 @@ pub struct WasiCtxBuilder(WasiCtx);
 
 impl WasiCtxBuilder {
     pub fn build(self) -> Result<WasiCtx, Error> {
+        use crate::file::TableFileExt;
+        let t = self.0.table();
+        for (fd, name) in ["stdin", "stdout", "stderr"].iter().enumerate() {
+            if t.get_file(fd as u32).is_err() {
+                return Err(anyhow::anyhow!(
+                    "Cannot build WasiCtx: Missing required file `{}`",
+                    name
+                ));
+            }
+        }
+        drop(t);
         Ok(self.0)
     }