cli: add back basic dump-ast support (#505)

usage:

```sh
echo select | squawk --debug=ast
```

which gives:

```json
{
  "stmts": [
    {
      "type": "SELECT"
    }
  ],
  "version": "0.1"
}
```

rel: #444

Author: sbdchd

crates/squawk/src/debug.rs

@@ -2,7 +2,8 @@ use std::{io, path::PathBuf};
 
 use annotate_snippets::{Level, Message, Renderer, Snippet};
 use anyhow::Result;
-use squawk_syntax::syntax_error::SyntaxError;
+use serde_json::json;
+use squawk_syntax::{ast::AstNode, syntax_error::SyntaxError};
 
 use crate::{
     file::{sql_from_path, sql_from_stdin},
@@ -13,11 +14,11 @@ pub(crate) fn debug<W: io::Write>(
     f: &mut W,
     paths: &[PathBuf],
     read_stdin: bool,
-    dump_ast: &DebugOption,
+    debug_option: &DebugOption,
     verbose: bool,
 ) -> Result<()> {
     let process_dump_ast = |sql: &str, filename: &str, f: &mut W| -> Result<()> {
-        match dump_ast {
+        match debug_option {
             DebugOption::Lex => {
                 let tokens = squawk_lexer::tokenize(sql);
                 let mut start = 0;
@@ -61,6 +62,9 @@ pub(crate) fn debug<W: io::Write>(
                     })?;
                 }
             }
+            DebugOption::Ast => {
+                dump_ast(f, sql)?;
+            }
         }
         Ok(())
     };
@@ -77,6 +81,30 @@ pub(crate) fn debug<W: io::Write>(
     Ok(())
 }
 
+fn dump_ast<W: io::Write>(f: &mut W, sql: &str) -> Result<()> {
+    let parse = squawk_syntax::SourceFile::parse(sql);
+    let file = parse.tree();
+
+    let stmts = file
+        .stmts()
+        .map(|stmt| {
+            // No api guarantees for now
+            json!({
+                "type": format!("{:?}", stmt.syntax().kind())
+            })
+        })
+        .collect::<Vec<_>>();
+
+    let output = json!({
+        "version": "0.1",
+        "stmts": stmts,
+    });
+
+    writeln!(f, "{}", serde_json::to_string_pretty(&output)?)?;
+
+    Ok(())
+}
+
 fn render_syntax_errors(
     errors: &[SyntaxError],
     filename: &str,
@@ -96,3 +124,28 @@ fn render_syntax_errors(
     }
     Ok(())
 }
+
+#[cfg(test)]
+mod test {
+    use insta::assert_snapshot;
+
+    use super::dump_ast;
+
+    #[test]
+    fn dump_ast_basic_output() {
+        let mut buffer = vec![];
+        dump_ast(
+            &mut buffer,
+            "
+select;
+insert into t values (1, 'a', true);
+update t set c = 10 where b = 5;
+delete from t;
+truncate t;
+",
+        )
+        .unwrap();
+        let output = String::from_utf8(buffer).expect("Invalid UTF-8");
+        assert_snapshot!(output);
+    }
+}

crates/squawk/src/main.rs

@@ -61,7 +61,8 @@ arg_enum! {
     #[derive(Debug, StructOpt)]
     pub enum DebugOption {
         Lex,
-        Parse
+        Parse,
+        Ast
     }
 }
 

crates/squawk/src/snapshots/squawk__debug__test__dump_ast_basic_output.snap

@@ -0,0 +1,24 @@
+---
+source: crates/squawk/src/debug.rs
+expression: output
+---
+{
+  "stmts": [
+    {
+      "type": "SELECT"
+    },
+    {
+      "type": "INSERT"
+    },
+    {
+      "type": "UPDATE"
+    },
+    {
+      "type": "DELETE"
+    },
+    {
+      "type": "TRUNCATE"
+    }
+  ],
+  "version": "0.1"
+}

crates/squawk_parser/src/lib.rs

@@ -24,26 +24,6 @@
 // IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
-// https://www.scattered-thoughts.net/writing/babys-second-wasm-compiler/
-//
-// https://craftinginterpreters.com/parsing-expressions.html
-//
-// see: https://github.com/rust-lang/rust-analyzer/blob/master/crates/parser/src/parser.rs
-// https://rust-analyzer.github.io/blog/2020/09/16/challeging-LR-parsing.html
-// https://github.com/rust-lang/rust-analyzer/blob/master/docs/dev/syntax.md
-// https://ericlippert.com/2012/06/08/red-green-trees/
-// https://github.com/swiftlang/swift/tree/5e2c815edfd758f9b1309ce07bfc01c4bc20ec23/lib/Syntax
-// https://swift-ast-explorer.com
-// https://github.com/rust-lang/rust-analyzer/blob/cf156a7a43f822e71309e50470ac34363da26727/docs/dev/syntax.md
-// https://github.com/kaleidawave/ezno/blob/8ce921e39c3d4e947063f206347b2932cee456ec/parser/src/lib.rs#L177
-// https://kaleidawave.github.io/posts/sets-types-and-type-checking/
-// https://github.com/m-novikov/tree-sitter-sql/tree/main
-// https://github.com/withered-magic/starpls/tree/79f47e12dab8be650804ce7fa931ee5e1e116eae/crates/starpls_parser/src
-// https://github.com/apache/datafusion-sqlparser-rs -- removes comments and whitespace :/
-
-// rust analyzer has a builtin doc test like thing where you generate snapshot
-// style tests from comments on top of grammar functions
-
 use drop_bomb::DropBomb;
 use event::Event;
 use grammar::OPERATOR_FIRST;

crates/squawk_syntax/README.md

@@ -0,0 +1,5 @@
+# squawk_syntax
+
+## related
+
+- https://github.com/rust-lang/rust-analyzer/blob/d2f17873ff19786a121fb3302f91779c1a1b957f/docs/book/src/contributing/syntax.md