subplotlib: Add external environment override for runcmd

In order to support runcmd environment overrides, we insert
them during scenario startup to match how the Python test
runtime does so.

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>

1 files changed, 17 insertions, 1 deletions

diff --git a/subplotlib/src/steplibrary/runcmd.rs b/subplotlib/src/steplibrary/runcmd.rs
index 8aabffc..c215f60 100644
--- a/subplotlib/src/steplibrary/runcmd.rs
+++ b/subplotlib/src/steplibrary/runcmd.rs
@@ -1,5 +1,6 @@
 //! Step library for running subprocesses as part of scenarios
 
+use env::vars_os;
 use regex::RegexBuilder;
 
 pub use super::datadir::Datadir;
@@ -23,6 +24,10 @@ pub struct Runcmd {
     stderr: Vec<u8>,
 }
 
+// Note, this prefix requires that the injection env vars must have
+// names which are valid unicode (and ideally ASCII)
+const ENV_INJECTION_PREFIX: &str = "SUBPLOT_ENV_";
+
 #[cfg(not(windows))]
 static DEFAULT_PATHS: &[&str] = &["/usr/bin", "/bin"];
 
@@ -41,6 +46,15 @@ impl ContextElement for Runcmd {
         self.env.insert("SHELL".into(), "/bin/sh".into());
         self.env
             .insert("PATH".into(), env::join_paths(DEFAULT_PATHS.iter())?);
+        // Having assembled the 'default' environment, override it with injected
+        // content from the calling environment.
+        for (k, v) in env::vars_os() {
+            if let Some(k) = k.to_str() {
+                if let Some(k) = k.strip_prefix(ENV_INJECTION_PREFIX) {
+                    self.env.insert(k.into(), v);
+                }
+            }
+        }
         Ok(())
     }
 }
@@ -94,7 +108,8 @@ pub fn try_to_run(context: &ScenarioContext, argv0: &str, args: &str) {
     proc.env_clear();
     proc.env("HOME", &datadir);
     proc.env("TMPDIR", &datadir);
-    let curpath = context.with(
+
+    let mut curpath = context.with(
         |runcmd: &Runcmd| {
             let mut curpath = None;
             for (k, v) in runcmd.env.iter() {
@@ -107,6 +122,7 @@ pub fn try_to_run(context: &ScenarioContext, argv0: &str, args: &str) {
         },
         false,
     )?;
+
     let path = context.with(
         |runcmd: &Runcmd| {
             Ok(env::join_paths(