add benchmarks for parsing (#250)

Author: joshuadavidthomas

crates/djls-templates/Cargo.toml

@@ -24,5 +24,9 @@ tempfile = { workspace = true }
 name = "lexer"
 harness = false
 
+[[bench]]
+name = "parser"
+harness = false
+
 [lints]
 workspace = true

crates/djls-templates/benches/parser.rs

@@ -0,0 +1,64 @@
+mod support;
+
+use divan::Bencher;
+use support::db::Db;
+use support::fixtures::template_fixtures;
+use support::fixtures::TemplateFixture;
+
+fn main() {
+    divan::main();
+}
+
+#[divan::bench(args = template_fixtures())]
+fn parse_template_fixture(fixture: &TemplateFixture) {
+    let mut db = Db::new();
+    let file = db.file_with_contents(fixture.path.clone(), &fixture.source);
+    if let Some(nodelist) = djls_templates::parse_template(&db, file) {
+        divan::black_box(nodelist.nodelist(&db).len());
+    }
+}
+
+#[divan::bench]
+fn parse_all_templates(bencher: Bencher) {
+    let fixtures = template_fixtures();
+    bencher.bench_local(|| {
+        let mut db = Db::new();
+        for fixture in fixtures {
+            let file = db.file_with_contents(fixture.path.clone(), &fixture.source);
+            if let Some(nodelist) = djls_templates::parse_template(&db, file) {
+                divan::black_box(nodelist.nodelist(&db).len());
+            }
+        }
+    });
+}
+
+#[divan::bench(args = template_fixtures())]
+fn parse_template_incremental(bencher: Bencher, fixture: &TemplateFixture) {
+    let mut db = Db::new();
+    let file = db.file_with_contents(fixture.path.clone(), &fixture.source);
+
+    // Prime caches with the baseline source so the benchmark measures the incremental path.
+    let _ = djls_templates::parse_template(&db, file);
+
+    let original = fixture.source.clone();
+    let modified = {
+        let mut text = original.clone();
+        text.push(' ');
+        text
+    };
+
+    let mut revision = 1_u64;
+    let mut use_modified = true;
+
+    bencher.bench_local(move || {
+        let contents = if use_modified { &modified } else { &original };
+        use_modified = !use_modified;
+
+        db.set_file_contents(file, contents, revision);
+        revision = revision.wrapping_add(1);
+
+        if let Some(nodelist) = djls_templates::parse_template(&db, file) {
+            divan::black_box(nodelist.nodelist(&db).len());
+        }
+    });
+}