feat: inject environment and /proc thing to wasm

crates/capabilities/Cargo.toml

@@ -15,7 +15,8 @@ http = "1"
 bytes = "1.4"
 futures-core = "0.3"
 anyhow = "1"
-libdd-capabilities = { git = "https://github.com/DataDog/libdatadog.git", tag = "v37.0.0" }
+libdd-capabilities = { git = "https://github.com/DataDog/libdatadog.git", branch = "jwiriath/APMSP-3780-inject-proc-env-stuff" }
+libdd-common = { git = "https://github.com/DataDog/libdatadog.git", branch = "jwiriath/APMSP-3780-inject-proc-env-stuff", default-features = false }
 
 [dev-dependencies]
 wasm-bindgen-test = "0.3"

crates/capabilities/src/entity.rs

@@ -0,0 +1,50 @@
+// Copyright 2026-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
+//! Seed libdatadog's entity-header store from Node.
+//!
+//! libdd-common's automatic detection reads `/proc/self/cgroup` and
+//! `DD_EXTERNAL_ENV` directly; neither is reachable from the
+//! `wasm32-unknown-unknown` sandbox. Node reads them itself and hands the raw
+//! values through this module *at wasm-module startup*, before any HTTP
+//! send. libdatadog then renders `datadog-container-id`, `datadog-entity-id`
+//! and `datadog-external-env` as part of the normal request head — no more
+//! post-render header rewrite in JS.
+
+use js_sys::Reflect;
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen(module = "/src/http_transport.js")]
+extern "C" {
+    // Returns an object `{ cgroupContent?: string, cgroupInode?: number, externalEnv?: string }`.
+    // Absent / null / undefined fields signal "not available" (not linux, not in a cgroup,
+    // env var unset). `cgroupInode` is a JS number so an inode past 2^53 would lose
+    // precision, but real inodes never approach that.
+    #[wasm_bindgen(js_name = "getEntityInputs")]
+    fn get_entity_inputs() -> JsValue;
+}
+
+/// Pull entity ingredients from Node and seed the libdd-common entity-header
+/// store. Call once, before the first HTTP send — libdd-common caches
+/// first-call-wins, so a later call (or a getter that latched to `None`
+/// before this ran) is a permanent no-op.
+pub fn init_from_js() {
+    let inputs = get_entity_inputs();
+
+    let cgroup_content = Reflect::get(&inputs, &JsValue::from_str("cgroupContent"))
+        .ok()
+        .and_then(|v| v.as_string());
+    let cgroup_inode = Reflect::get(&inputs, &JsValue::from_str("cgroupInode"))
+        .ok()
+        .and_then(|v| v.as_f64())
+        .map(|n| n as u64);
+    let external_env = Reflect::get(&inputs, &JsValue::from_str("externalEnv"))
+        .ok()
+        .and_then(|v| v.as_string());
+
+    libdd_common::entity_id::init_entity_inputs(
+        cgroup_content.as_deref(),
+        cgroup_inode,
+        external_env.as_deref(),
+    );
+}