Allow shell to changed via config.

This commit allows me (and others!) to change which shell to use to run the tests via the `config`. This is useful for platforms that do not have the default shell, `bash`, present.

To test this I decided that if the `lit` crate is happy to rely on `bash`, it makes sense that `sh` would also be present. So I added an additional run of the integration tests using `sh` to prove that it works.

Author: sheredom

src/config.rs

@@ -47,6 +47,8 @@ pub struct Config
     /// Whether messages on the standard error streams emitted during test runs
     /// should always be shown.
     pub always_show_stderr: bool,
+    /// Which shell to use (defaults to 'bash').
+    pub shell: String,
 }
 
 /// A function which can dynamically define newly used variables in a test.
@@ -151,6 +153,7 @@ impl Default for Config
             always_show_stderr: false,
             truncate_output_context_to_number_of_lines: Some(DEFAULT_MAX_OUTPUT_CONTEXT_LINE_COUNT),
             extra_executable_search_paths,
+            shell: "bash".to_string(),
         }
     }
 }

src/run/legacy_test_evaluator.rs

@@ -7,8 +7,6 @@ use crate::{parse, vars};
 
 use std;
 
-const SHELL: &'static str = "bash";
-
 pub struct TestEvaluator
 {
     pub invocation: Invocation,
@@ -40,7 +38,7 @@ impl TestEvaluator
             Err(e) => match e.kind() {
                 std::io::ErrorKind::NotFound => {
                     return TestResultKind::Error(
-                        format!("shell '{}' does not exist", SHELL).into(),
+                        format!("shell '{}' does not exist", &config.shell).into(),
                     );
                 },
                 _ => return TestResultKind::Error(e.into()),
@@ -73,7 +71,7 @@ impl TestEvaluator
 
         let command_line: String = vars::resolve::invocation(&self.invocation, &config, &mut variables);
 
-        let mut cmd = process::Command::new("bash");
+        let mut cmd = process::Command::new(&config.shell);
         cmd.args(&["-c", &command_line]);
 
         if let Ok(current_exe) = env::current_exe() {

src/run/test_evaluator.rs

@@ -10,8 +10,6 @@ use std::{collections::HashMap, env, fs, process};
 mod state;
 #[cfg(test)] mod state_tests;
 
-const DEFAULT_SHELL: &'static str = "bash";
-
 /// Responsible for evaluating specific tests and collecting
 /// the results.
 #[derive(Clone)]
@@ -32,7 +30,7 @@ pub fn execute_tests<'test>(test_file: &'test TestFile, config: &Config) -> Vec<
         let mut test_run_state = TestRunState::new(initial_variables);
         let (command, command_line) = self::build_command(invocation, test_file, config);
 
-        let (program_output, execution_result) = self::collect_output(command, command_line.clone());
+        let (program_output, execution_result) = self::collect_output(command, command_line.clone(), config);
 
         test_run_state.append_program_output(&program_output.stdout);
         test_run_state.append_program_stderr(&program_output.stderr);
@@ -97,14 +95,15 @@ fn run_test_checks(
 fn collect_output(
     mut command: process::Command,
     command_line: CommandLine,
+    config: &Config,
 ) -> (ProgramOutput, TestResultKind) {
     let mut test_result_kind = TestResultKind::Pass;
 
     let output = match command.output() {
         Ok(o) => o,
         Err(e) => {
             let error_message = match e.kind() {
-                std::io::ErrorKind::NotFound => format!("shell '{}' does not exist", DEFAULT_SHELL).into(),
+                std::io::ErrorKind::NotFound => format!("shell '{}' does not exist", &config.shell).into(),
                 _ => e.to_string(),
             };
 
@@ -142,7 +141,7 @@ fn build_command(invocation: &Invocation,
 
     let command_line: String = vars::resolve::invocation(invocation, &config, &mut variables);
 
-    let mut cmd = process::Command::new(DEFAULT_SHELL);
+    let mut cmd = process::Command::new(&config.shell);
     cmd.args(&["-c", &command_line]);
 
     if !config.extra_executable_search_paths.is_empty() {

tests/integration_tests.rs

@@ -14,4 +14,14 @@ fn integration_tests() {
             config.add_extension(ext);
         }
     }).expect("unit test(s) failed");
+
+    // Now run the tests again but use a custom shell instead.
+    run::tests(lit::event_handler::Default::default(), |config| {
+        config.add_search_path(format!("{}/integration-tests", CRATE_PATH));
+        for ext in lit::INTEGRATION_TEST_FILE_EXTENSIONS {
+            config.add_extension(ext);
+        }
+
+        config.shell = "sh".to_string();
+    }).expect("unit test(s) failed");
 }