Shared: Add integration test for shared extractor

This is a very basic test but provides some confidence that the extractor is
working.

shared/tree-sitter-extractor/Cargo.toml

@@ -16,3 +16,7 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 chrono = { version = "0.4.19", features = ["serde"] }
 num_cpus = "1.14.0"
+
+[dev-dependencies]
+tree-sitter-ql = { git = "https://github.com/tree-sitter/tree-sitter-ql" }
+rand = "0.8.5"

shared/tree-sitter-extractor/tests/integration_test.rs

@@ -0,0 +1,73 @@
+use std::fs::File;
+use std::io::{Write, Read, BufRead};
+use std::path::{Path, PathBuf};
+
+use codeql_extractor::extractor::simple;
+use flate2::read::GzDecoder;
+use tree_sitter_ql;
+
+
+
+/// An very simple happy-path test.
+/// We run the extractor using the tree-sitter-ql grammar and a single source file,
+/// and check that we get a reasonable-looking trap file in the expected location.
+#[test]
+fn simple_extractor() {
+    let language = simple::LanguageSpec {
+        prefix: "ql",
+        ts_language: tree_sitter_ql::language(),
+        node_types: tree_sitter_ql::NODE_TYPES,
+        file_extensions: vec!["qll".into()],
+    };
+
+    let root_dir = std::env::temp_dir().join(format!("codeql-extractor-{}", rand::random::<u16>()));
+    std::fs::create_dir_all(&root_dir).unwrap();
+
+    let trap_dir = create_dir(&root_dir, "trap");
+    let source_archive_dir = create_dir(&root_dir, "src");
+
+    // Create foo.qll source file
+    let foo_qll = {
+        let path = source_archive_dir.join("foo.qll");
+        let mut file = File::create(&path).expect("Failed to create src/foo.qll");
+        file.write_all(b"predicate p(int a) { a = 1 }").expect("Failed to write to foo.qll");
+        PathBuf::from(path)
+    };
+
+    let file_list = {
+        let path = root_dir.join("files.txt");
+        let mut file = File::create(&path).expect("Failed to create files.txt");
+        file.write_all(foo_qll.as_path().display().to_string().as_bytes()).expect("Failed to write to files.txt");
+        path
+    };
+
+    let extractor = simple::Extractor {
+        prefix: "ql".to_string(),
+        languages: vec![language],
+        trap_dir,
+        source_archive_dir,
+        file_list,
+    };
+
+    // The extractor should run successfully
+    extractor.run().unwrap();
+
+    // Check for the presence of $root/trap/$root/src/foo.qll
+    {
+        let  root_dir_relative  = {
+            let r = root_dir.as_path().display().to_string();
+            r.strip_prefix("/").unwrap().to_string()
+        };
+        let foo_qll_trap_gz = root_dir.join("trap").join(root_dir_relative).join("src/foo.qll.trap.gz");
+        let mut decoder = GzDecoder::new(File::open(foo_qll_trap_gz).expect("Failed to open foo.qll.trap.gz"));
+        let mut first_line = [0; 31];
+        decoder.read_exact(&mut first_line).expect("Failed to read from foo.qll.trap.gz");
+        assert_eq!(first_line.as_slice(), b"// Auto-generated TRAP file for");
+    }
+}
+
+fn create_dir(root: &Path, path: impl AsRef<Path>) -> PathBuf {
+    let full_path = root.join(path);
+    std::fs::create_dir_all(&full_path).expect("Failed to create directory");
+    full_path.into()
+}