add test_util to make examples work well

examples/examples/standalone-sql.rs

@@ -16,6 +16,7 @@
 // under the License.
 
 use ballista::prelude::{BallistaConfig, BallistaContext, Result};
+use ballista_examples::test_util;
 use datafusion::prelude::CsvReadOptions;
 
 #[tokio::main]
@@ -26,10 +27,12 @@ async fn main() -> Result<()> {
 
     let ctx = BallistaContext::standalone(&config, 2).await?;
 
+    let testdata = test_util::examples_test_data();
+
     // register csv file with the execution context
     ctx.register_csv(
         "test",
-        "testdata/aggregate_test_100.csv",
+        &format!("{testdata}/aggregate_test_100.csv"),
         CsvReadOptions::new(),
     )
     .await?;

examples/src/lib.rs

@@ -0,0 +1,18 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+pub mod test_util;

examples/src/test_util.rs

@@ -0,0 +1,89 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use std::env;
+use std::error::Error;
+use std::path::PathBuf;
+
+/// Returns the parquet test data directory, which is by default
+/// stored in a git submodule rooted at
+/// `examples/testdata`.
+///
+/// The default can be overridden by the optional environment variable
+/// `EXAMPLES_TEST_DATA`
+///
+/// panics when the directory can not be found.
+///
+/// Example:
+/// ```
+/// use ballista_examples::test_util;
+/// let testdata = test_util::examples_test_data();
+/// let filename = format!("{testdata}/aggregate_test_100.csv");
+/// assert!(std::path::PathBuf::from(filename).exists());
+/// ```
+pub fn examples_test_data() -> String {
+    match get_data_dir("EXAMPLES_TEST_DATA", "testdata") {
+        Ok(pb) => pb.display().to_string(),
+        Err(err) => panic!("failed to get examples test data dir: {err}"),
+    }
+}
+
+/// Returns a directory path for finding test data.
+///
+/// udf_env: name of an environment variable
+///
+/// submodule_dir: fallback path (relative to CARGO_MANIFEST_DIR)
+///
+///  Returns either:
+/// The path referred to in `udf_env` if that variable is set and refers to a directory
+/// The submodule_data directory relative to CARGO_MANIFEST_PATH
+fn get_data_dir(udf_env: &str, submodule_data: &str) -> Result<PathBuf, Box<dyn Error>> {
+    // Try user defined env.
+    if let Ok(dir) = env::var(udf_env) {
+        let trimmed = dir.trim().to_string();
+        if !trimmed.is_empty() {
+            let pb = PathBuf::from(trimmed);
+            if pb.is_dir() {
+                return Ok(pb);
+            } else {
+                return Err(format!(
+                    "the data dir `{}` defined by env {udf_env} not found",
+                    pb.display()
+                )
+                .into());
+            }
+        }
+    }
+
+    // The env is undefined or its value is trimmed to empty, let's try default dir.
+
+    // env "CARGO_MANIFEST_DIR" is "the directory containing the manifest of your package",
+    // set by `cargo run` or `cargo test`, see:
+    // https://doc.rust-lang.org/cargo/reference/environment-variables.html
+    let dir = env!("CARGO_MANIFEST_DIR");
+
+    let pb = PathBuf::from(dir).join(submodule_data);
+    if pb.is_dir() {
+        Ok(pb)
+    } else {
+        Err(format!(
+            "env `{udf_env}` is undefined or has empty value, and the pre-defined data dir `{}` not found\n\
+             HINT: try running `git submodule update --init`",
+            pb.display(),
+        ).into())
+    }
+}