Make docker build only run once even if there are multiple tests using it

1 files changed, 51 insertions, 20 deletions

diff --git a/tests/server_shell.rs b/tests/server_shell.rs
index 858f123..ae77a6a 100644
--- a/tests/server_shell.rs
+++ b/tests/server_shell.rs
@@ -1,7 +1,12 @@
-use anyhow::{bail, Result};
-use assert_cmd::{cargo::cargo_bin, Command};
+use anyhow::Result;
+use assert_cmd::cargo::cargo_bin;
 use rexpect::session::{spawn_command, PtySession};
+use std::{io, path, sync::Once};
 use tempfile::TempDir;
+use thiserror::Error;
+
+static BUILD_DOCKER: Once = Once::new();
+static mut BUILD_DOCKER_RESULT: Result<(), DockerBuildError> = Ok(());
 
 struct TestContext {
     workdir: TempDir,
@@ -9,27 +14,53 @@ struct TestContext {
     docker_process: PtySession,
 }
 
-fn build_docker_image() -> Result<()> {
-    let mut command = std::process::Command::new("docker");
-
-    let absolute_shell_path = cargo_bin(env!("CARGO_PKG_NAME"));
-    let relative_shell_path = absolute_shell_path.strip_prefix(std::fs::canonicalize(".")?)?;
-    command.args([
-        "build",
-        "--quiet",
-        "-t",
-        "shackle-server",
-        "--build-arg",
-        &format!("SHELL={}", relative_shell_path.display()),
-        "./",
-    ]);
+#[derive(Error, Debug, Clone)]
+pub enum DockerBuildError {
+    #[error(transparent)]
+    StripPrefixError(#[from] path::StripPrefixError),
+    #[error("IO Error: `{0}`")]
+    IoError(String),
+    #[error("Failed to build dockerfile")]
+    CliError,
+}
 
-    let status = command.status()?;
-    if !status.success() {
-        bail!("Failed to build dockerfile");
+impl From<io::Error> for DockerBuildError {
+    fn from(e: io::Error) -> Self {
+        DockerBuildError::IoError(e.to_string())
     }
+}
 
-    Ok(())
+fn build_docker_image() -> Result<(), DockerBuildError> {
+    let build_docker = || {
+        let mut command = std::process::Command::new("docker");
+
+        let absolute_shell_path = cargo_bin(env!("CARGO_PKG_NAME"));
+        let relative_shell_path = absolute_shell_path.strip_prefix(std::fs::canonicalize(".")?)?;
+        command.args([
+            "build",
+            "--quiet",
+            "-t",
+            "shackle-server",
+            "--build-arg",
+            &format!("SHELL={}", relative_shell_path.display()),
+            "./",
+        ]);
+
+        let status = command.status()?;
+        if status.success() {
+            Ok(())
+        } else {
+            Err(DockerBuildError::CliError)
+        }
+    };
+
+    // Based on this example: https://doc.rust-lang.org/std/sync/struct.Once.html#examples-1
+    unsafe {
+        BUILD_DOCKER.call_once(|| {
+            BUILD_DOCKER_RESULT = build_docker();
+        });
+        BUILD_DOCKER_RESULT.clone()
+    }
 }
 
 fn spawn_ssh_server() -> Result<TestContext> {