Make celq work without 'this'

Author: IvanIsCoding

docs/manual.md

@@ -432,7 +432,7 @@ celq --from-yaml 'this[1].tags' < multi.yaml
 With that being said, `celq` can pretty-print JSON via the `-p` flag:
 
 ```bash
-echo '{"a": 1, "b": 2}' | celq -p 'this'
+echo '{"a": 1, "b": 2}' | celq -p
 ```
 
 Outputs:
@@ -467,7 +467,7 @@ grocery_list_cli --item $FRUIT --quantity 5
 
 For example, to chain `celq` with ripgrep to find all fields containing `regularMarket`:
 ```bash
-celq -g 'this' < yfinance.json | rg '\bregularMarket\w*'
+celq -g  < yfinance.json | rg '\bregularMarket\w*'
 ```
 
 Outputs:
@@ -481,7 +481,7 @@ json.chart.result[0].meta.regularMarketTime = 1767387600;
 One interesting property about `--greppable` is that the output is valid JavaScript code. This unlocks use cases such as embedding TOML, YAML, and JSON5 configs as JavaScript source code. For example:
 
 ```bash
-celq --from-toml -g -S 'this' < Cargo.toml > cargo_toml.js
+celq --from-toml -g -S  < Cargo.toml > cargo_toml.js
 ```
 
 Writes the following to `cargo_toml.js`:
@@ -506,7 +506,7 @@ For NDJSON inputs, `--greppable` outputs only the last line. This happens to pre
 For example:
 
 ```bash
-celq -g 'this' < yfinance.json | rg '\bregularMarket\w*' | celq --from-gron -S -p 'this'
+celq -g  < yfinance.json | rg '\bregularMarket\w*' | celq --from-gron -S -p 
 ```
 
 Outputs:

src/cli.rs

@@ -77,7 +77,6 @@ impl std::str::FromStr for Argument {
     long_about = None,
     group(
         ArgGroup::new("program")
-            .required(true)
             .args(&["expression", "from_file"])
     ),
     group(
@@ -173,7 +172,7 @@ pub struct Cli {
     pub no_extensions: bool,
 
     /// CEL expression to evaluate
-    #[arg(value_name = "expr")]
+    #[arg(value_name = "expr", default_value = "this")]
     pub expression: Option<String>,
 }
 

tests/golden.rs

@@ -893,6 +893,14 @@ test!(
     "[10,15,20]"
 );
 
+// Default expr test
+test!(
+    default_expression,
+    &[],
+    r#"{"value":100}"#,
+    r#"{"value":100}"#
+);
+
 #[test]
 fn test_boolean_false_exit_code() -> io::Result<()> {
     let mut child = process::Command::new(env!("CARGO_BIN_EXE_celq"))