Make the cli example print JSON (#197)

...via the new json_example feature - to make it easier to try out the parser without coding.

Cargo.toml

@@ -18,10 +18,18 @@ edition = "2018"
 name = "sqlparser"
 path = "src/lib.rs"
 
+[features]
+# Enable JSON output in the `cli` example:
+json_example = ["serde_json", "serde"]
+
 [dependencies]
 bigdecimal = { version = "0.1.0", features = ["serde"], optional = true }
 log = "0.4.5"
 serde = { version = "1.0", features = ["derive"], optional = true }
+# serde_json is only used in examples/cli, but we have to put it outside
+# of dev-dependencies because of
+# https://github.com/rust-lang/cargo/issues/1596
+serde_json = { version = "1.0", optional = true }
 
 [dev-dependencies]
 simple_logger = "1.0.1"

README.md

@@ -40,6 +40,12 @@ This outputs
 AST: [Query(Query { ctes: [], body: Select(Select { distinct: false, projection: [UnnamedExpr(Identifier("a")), UnnamedExpr(Identifier("b")), UnnamedExpr(Value(Long(123))), UnnamedExpr(Function(Function { name: ObjectName(["myfunc"]), args: [Identifier("b")], over: None, distinct: false }))], from: [TableWithJoins { relation: Table { name: ObjectName(["table_1"]), alias: None, args: [], with_hints: [] }, joins: [] }], selection: Some(BinaryOp { left: BinaryOp { left: Identifier("a"), op: Gt, right: Identifier("b") }, op: And, right: BinaryOp { left: Identifier("b"), op: Lt, right: Value(Long(100)) } }), group_by: [], having: None }), order_by: [OrderByExpr { expr: Identifier("a"), asc: Some(false) }, OrderByExpr { expr: Identifier("b"), asc: None }], limit: None, offset: None, fetch: None })]
 ```
 
+## Command line
+To parse a file and dump the results as JSON:
+```
+$ cargo run --feature json_example --example cli FILENAME.sql [--dialectname]
+```
+
 ## SQL compliance
 
 SQL was first standardized in 1987, and revisions of the standard have been

examples/cli.rs

@@ -23,8 +23,16 @@ fn main() {
     simple_logger::init().unwrap();
 
     let filename = std::env::args().nth(1).expect(
-        "No arguments provided!\n\n\
-         Usage: cargo run --example cli FILENAME.sql [--dialectname]",
+        r#"
+No arguments provided!
+
+Usage:
+$ cargo run --example cli FILENAME.sql [--dialectname]
+
+To print the parse results as JSON:
+$ cargo run --feature json_example --example cli FILENAME.sql [--dialectname]
+
+"#,
     );
 
     let dialect: Box<dyn Dialect> = match std::env::args().nth(2).unwrap_or_default().as_ref() {
@@ -56,7 +64,17 @@ fn main() {
                     .collect::<Vec<_>>()
                     .join("\n")
             );
-            println!("Parse results:\n{:#?}", statements);
+
+            if cfg!(feature = "json_example") {
+                #[cfg(feature = "json_example")]
+                {
+                    let serialized = serde_json::to_string_pretty(&statements).unwrap();
+                    println!("Serialized as JSON:\n{}", serialized);
+                }
+            } else {
+                println!("Parse results:\n{:#?}", statements);
+            }
+
             std::process::exit(0);
         }
         Err(e) => {