Implement `missing` and `env:VAR` imports

3 files changed, 20 insertions, 8 deletions

diff --git a/dhall/src/error/mod.rs b/dhall/src/error/mod.rs
index 8829d47..5632ea6 100644
--- a/dhall/src/error/mod.rs
+++ b/dhall/src/error/mod.rs
@@ -26,6 +26,8 @@ pub(crate) enum ErrorKind {
 
 #[derive(Debug)]
 pub(crate) enum ImportError {
+    Missing,
+    MissingEnvVar,
     UnexpectedImport(Import<()>),
     ImportCycle(ImportStack, Import<()>),
 }
diff --git a/dhall/src/semantics/resolve/resolve.rs b/dhall/src/semantics/resolve/resolve.rs
index b27dd2c..bf7aabb 100644
--- a/dhall/src/semantics/resolve/resolve.rs
+++ b/dhall/src/semantics/resolve/resolve.rs
@@ -1,6 +1,7 @@
 use itertools::Itertools;
 use std::borrow::Cow;
-use std::path::{Path, PathBuf};
+use std::env;
+use std::path::PathBuf;
 
 use crate::error::ErrorBuilder;
 use crate::error::{Error, ImportError};
@@ -47,8 +48,21 @@ fn resolve_one_import(
                         FilePrefix::Here => cwd.join(path_buf),
                         _ => unimplemented!("{:?}", import),
                     };
-                    Ok(load_import(env, &path_buf)?)
+
+                    let parsed = Parsed::parse_file(&path_buf)?;
+                    let typed = resolve_with_env(env, parsed)?.typecheck()?;
+                    Ok((typed.normalize().to_hir(), typed.ty().clone()))
+                }
+                ImportLocation::Env(var_name) => {
+                    let val = match env::var(var_name) {
+                        Ok(val) => val,
+                        Err(_) => Err(ImportError::MissingEnvVar)?,
+                    };
+                    let parsed = Parsed::parse_str(&val)?;
+                    let typed = resolve_with_env(env, parsed)?.typecheck()?;
+                    Ok((typed.normalize().to_hir(), typed.ty().clone()))
                 }
+                ImportLocation::Missing => Err(ImportError::Missing.into()),
                 _ => unimplemented!("{:?}", import),
             }
         }
@@ -122,12 +136,6 @@ fn resolve_one_import(
     }
 }
 
-fn load_import(env: &mut ImportEnv, f: &Path) -> Result<TypedHir, Error> {
-    let parsed = Parsed::parse_file(f)?;
-    let typed = resolve_with_env(env, parsed)?.typecheck()?;
-    Ok((typed.normalize().to_hir(), typed.ty().clone()))
-}
-
 /// Desugar the first level of the expression.
 fn desugar(expr: &Expr) -> Cow<'_, Expr> {
     match expr.kind() {
diff --git a/dhall/src/tests.rs b/dhall/src/tests.rs
index 044b185..369c6cc 100644
--- a/dhall/src/tests.rs
+++ b/dhall/src/tests.rs
@@ -247,6 +247,8 @@ fn run_test(test: Test) -> Result<()> {
     env::set_current_dir(
         PathBuf::from(env!("CARGO_MANIFEST_DIR")).parent().unwrap(),
     )?;
+    // Set environment variable for import tests.
+    env::set_var("DHALL_TEST_VAR", "6 * 7");
 
     match test {
         ParserSuccess(expr, expected) => {