Restrict closure expression to be something like {|| ...} (#8290)

# Description

As title, closes: #7921 closes: #8273

# User-Facing Changes

when define a closure without pipe, nushell will raise error for now:
```
❯ let x = {ss ss}
Error: nu::parser::closure_missing_pipe

  × Missing || inside closure
   ╭─[entry #2:1:1]
 1 │ let x = {ss ss}
   ·         ───┬───
   ·            ╰── Parsing as a closure, but || is missing
   ╰────
  help: Try add || to the beginning of closure
```

`any`, `each`, `all`, `where` command accepts closure, it forces user
input closure like `{||`, or parse error will returned.
```
❯ {major:2, minor:1, patch:4} | values | each { into string }
Error: nu::parser::closure_missing_pipe

  × Missing || inside closure
   ╭─[entry #4:1:1]
 1 │ {major:2, minor:1, patch:4} | values | each { into string }
   ·                                             ───────┬───────
   ·                                                    ╰── Parsing as a closure, but || is missing
   ╰────
  help: Try add || to the beginning of closure
```

`with-env`, `do`, `def`, `try` are special, they still remain the same,
although it says that it accepts a closure, but they don't need to be
written like `{||`, it's more likely a block but can capture variable
outside of scope:
```
❯ def test [input] { echo [0 1 2] | do { do { echo $input } } }; test aaa
aaa
```

Just realize that It's a big breaking change, we need to update config
and scripts...

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-cmd-lang/src/core_commands/do_.rs

@@ -22,7 +22,11 @@ impl Command for Do {
 
     fn signature(&self) -> Signature {
         Signature::build("do")
-            .required("closure", SyntaxShape::Any, "the closure to run")
+            .required(
+                "closure",
+                SyntaxShape::OneOf(vec![SyntaxShape::Closure(None), SyntaxShape::Any]),
+                "the closure to run",
+            )
             .input_output_types(vec![(Type::Any, Type::Any)])
             .switch(
                 "ignore-errors",

crates/nu-cmd-lang/src/core_commands/try_.rs

@@ -26,7 +26,10 @@ impl Command for Try {
                 "catch_block",
                 SyntaxShape::Keyword(
                     b"catch".to_vec(),
-                    Box::new(SyntaxShape::Closure(Some(vec![SyntaxShape::Any]))),
+                    Box::new(SyntaxShape::OneOf(vec![
+                        SyntaxShape::Closure(None),
+                        SyntaxShape::Closure(Some(vec![SyntaxShape::Any])),
+                    ])),
                 ),
                 "block to run if try block fails",
             )

crates/nu-command/src/debug/timeit.rs

@@ -111,7 +111,7 @@ fn test_time_closure() {
     use nu_test_support::{nu, nu_repl_code, playground::Playground};
     Playground::setup("test_time_closure", |dirs, _| {
         let inp = [
-            r#"[2 3 4] | timeit { to nuon | save foo.txt }"#,
+            r#"[2 3 4] | timeit {|_| to nuon | save foo.txt }"#,
             "open foo.txt",
         ];
         let actual_repl = nu!(cwd: dirs.test(), nu_repl_code(&inp));

crates/nu-command/src/filters/all.rs

@@ -45,7 +45,7 @@ impl Command for All {
             },
             Example {
                 description: "Check that each item is a string",
-                example: "[foo bar 2 baz] | all { ($in | describe) == 'string' }",
+                example: "[foo bar 2 baz] | all {|| ($in | describe) == 'string' }",
                 result: Some(Value::test_bool(false)),
             },
             Example {

crates/nu-command/src/filters/any.rs

@@ -45,7 +45,7 @@ impl Command for Any {
             },
             Example {
                 description: "Check that any item is a string",
-                example: "[1 2 3 4] | any { ($in | describe) == 'string' }",
+                example: "[1 2 3 4] | any {|| ($in | describe) == 'string' }",
                 result: Some(Value::test_bool(false)),
             },
             Example {

crates/nu-command/src/filters/each.rs

@@ -74,7 +74,7 @@ with 'transpose' first."#
                 }),
             },
             Example {
-                example: "{major:2, minor:1, patch:4} | values | each { into string }",
+                example: "{major:2, minor:1, patch:4} | values | each {|| into string }",
                 description: "Produce a list of values in the record, converted to string",
                 result: Some(Value::List {
                     vals: vec![

crates/nu-command/tests/commands/all.rs

@@ -85,7 +85,7 @@ fn works_with_1_param_blocks() {
 fn works_with_0_param_blocks() {
     let actual = nu!(
         cwd: ".", pipeline(
-        r#"[1 2 3] | all { print $in | true }"#
+        r#"[1 2 3] | all {|| print $in | true }"#
     ));
 
     assert_eq!(actual.out, "123true");
@@ -105,7 +105,7 @@ fn early_exits_with_1_param_blocks() {
 fn early_exits_with_0_param_blocks() {
     let actual = nu!(
         cwd: ".", pipeline(
-        r#"[1 2 3] | all { print $in | false }"#
+        r#"[1 2 3] | all {|| print $in | false }"#
     ));
 
     assert_eq!(actual.out, "1false");
@@ -125,7 +125,7 @@ fn all_uses_enumerate_index() {
 fn unique_env_each_iteration() {
     let actual = nu!(
         cwd: "tests/fixtures/formats",
-        "[1 2] | all { print ($env.PWD | str ends-with 'formats') | cd '/' | true } | to nuon"
+        "[1 2] | all {|| print ($env.PWD | str ends-with 'formats') | cd '/' | true } | to nuon"
     );
 
     assert_eq!(actual.out, "truetruetrue");

crates/nu-command/tests/commands/any.rs

@@ -61,7 +61,7 @@ fn works_with_1_param_blocks() {
 fn works_with_0_param_blocks() {
     let actual = nu!(
         cwd: ".", pipeline(
-        r#"[1 2 3] | any { print $in | false }"#
+        r#"[1 2 3] | any {|| print $in | false }"#
     ));
 
     assert_eq!(actual.out, "123false");
@@ -81,7 +81,7 @@ fn early_exits_with_1_param_blocks() {
 fn early_exits_with_0_param_blocks() {
     let actual = nu!(
         cwd: ".", pipeline(
-        r#"[1 2 3] | any { print $in | true }"#
+        r#"[1 2 3] | any {|| print $in | true }"#
     ));
 
     assert_eq!(actual.out, "1true");
@@ -101,7 +101,7 @@ fn any_uses_enumerate_index() {
 fn unique_env_each_iteration() {
     let actual = nu!(
         cwd: "tests/fixtures/formats",
-        "[1 2] | any { print ($env.PWD | str ends-with 'formats') | cd '/' | false } | to nuon"
+        "[1 2] | any {|| print ($env.PWD | str ends-with 'formats') | cd '/' | false } | to nuon"
     );
 
     assert_eq!(actual.out, "truetruefalse");

crates/nu-command/tests/commands/bytes/starts_with.rs

@@ -79,7 +79,7 @@ fn long_stream_binary_overflow() {
     let actual = nu!(
         cwd: ".",
         r#"
-            nu --testbin repeater (0x[01]) 32768 | bytes starts-with (0..32768 | each { 0x[01] } | bytes collect)
+            nu --testbin repeater (0x[01]) 32768 | bytes starts-with (0..32768 | each {|| 0x[01] } | bytes collect)
         "#
     );
 
@@ -92,7 +92,7 @@ fn long_stream_binary_exact() {
     let actual = nu!(
         cwd: ".",
         r#"
-            nu --testbin repeater (0x[01020304]) 8192 | bytes starts-with (0..<8192 | each { 0x[01020304] } | bytes collect)
+            nu --testbin repeater (0x[01020304]) 8192 | bytes starts-with (0..<8192 | each {|| 0x[01020304] } | bytes collect)
         "#
     );
 
@@ -105,7 +105,7 @@ fn long_stream_string_exact() {
     let actual = nu!(
         cwd: ".",
         r#"
-            nu --testbin repeater hell 8192 | bytes starts-with (0..<8192 | each { "hell" | into binary } | bytes collect)
+            nu --testbin repeater hell 8192 | bytes starts-with (0..<8192 | each {|| "hell" | into binary } | bytes collect)
         "#
     );
 
@@ -118,8 +118,8 @@ fn long_stream_mixed_exact() {
     let actual = nu!(
         cwd: ".",
         r#"
-            let binseg = (0..<2048 | each { 0x[003d9fbf] } | bytes collect)
-            let strseg = (0..<2048 | each { "hell" | into binary } | bytes collect)
+            let binseg = (0..<2048 | each {|| 0x[003d9fbf] } | bytes collect)
+            let strseg = (0..<2048 | each {|| "hell" | into binary } | bytes collect)
 
             nu --testbin repeat_bytes 003d9fbf 2048 68656c6c 2048 | bytes starts-with (bytes build $binseg $strseg)
         "#
@@ -138,8 +138,8 @@ fn long_stream_mixed_overflow() {
     let actual = nu!(
         cwd: ".",
         r#"
-            let binseg = (0..<2048 | each { 0x[003d9fbf] } | bytes collect)
-            let strseg = (0..<2048 | each { "hell" | into binary } | bytes collect)
+            let binseg = (0..<2048 | each {|| 0x[003d9fbf] } | bytes collect)
+            let strseg = (0..<2048 | each {|| "hell" | into binary } | bytes collect)
 
             nu --testbin repeat_bytes 003d9fbf 2048 68656c6c 2048 | bytes starts-with (bytes build $binseg $strseg 0x[01])
         "#

crates/nu-command/tests/commands/empty.rs

@@ -6,7 +6,7 @@ fn reports_emptiness() {
         cwd: ".", pipeline(
         r#"
             [[] '' {} null]
-            | all {
+            | all {||
               is-empty
             }
         "#
@@ -21,7 +21,7 @@ fn reports_nonemptiness() {
         cwd: ".", pipeline(
         r#"
             [[1] ' ' {a:1} 0]
-            | any {
+            | any {||
               is-empty
             }
         "#
@@ -36,7 +36,7 @@ fn reports_emptiness_by_columns() {
         cwd: ".", pipeline(
         r#"
             [{a:1 b:null c:null} {a:2 b:null c:null}]
-            | any {
+            | any {||
               is-empty b c
             }
         "#
@@ -51,7 +51,7 @@ fn reports_nonemptiness_by_columns() {
         cwd: ".", pipeline(
         r#"
             [{a:1 b:null c:3} {a:null b:5 c:2}]
-            | any {
+            | any {||
               is-empty a b
             }
         "#

crates/nu-command/tests/commands/group_by.rs

@@ -61,7 +61,7 @@ fn errors_if_given_unknown_column_name() {
             cwd: dirs.test(), pipeline(
             r#"
                 open los_tres_caballeros.json
-                | group-by { get nu.releases.version }
+                | group-by {|| get nu.releases.version }
             "#
         ));
 

crates/nu-command/tests/commands/ls.rs

@@ -548,7 +548,7 @@ fn list_ignores_ansi() {
         let actual = nu!(
             cwd: dirs.test(), pipeline(
             r#"
-                ls | find .txt | each { ls $in.name } 
+                ls | find .txt | each {|| ls $in.name } 
             "#
         ));
 

crates/nu-command/tests/commands/update.rs

@@ -44,7 +44,7 @@ fn sets_the_column_from_a_block_full_stream_output() {
         cwd: "tests/fixtures/formats", pipeline(
         r#"
             {content: null}
-            | update content { open --raw cargo_sample.toml | lines | first 5 }
+            | update content {|| open --raw cargo_sample.toml | lines | first 5 }
             | get content.1
             | str contains "nu"
         "#

crates/nu-command/tests/commands/upsert.rs

@@ -44,7 +44,7 @@ fn sets_the_column_from_a_block_full_stream_output() {
         cwd: "tests/fixtures/formats", pipeline(
         r#"
             {content: null}
-            | upsert content { open --raw cargo_sample.toml | lines | first 5 }
+            | upsert content {|| open --raw cargo_sample.toml | lines | first 5 }
             | get content.1
             | str contains "nu"
         "#

crates/nu-command/tests/commands/where_.rs

@@ -35,7 +35,7 @@ fn where_inside_block_works() {
 fn filters_with_0_arity_block() {
     let actual = nu!(
         cwd: ".",
-        "[1 2 3 4] | where { $in < 3 } | to nuon"
+        "[1 2 3 4] | where {|| $in < 3 } | to nuon"
     );
 
     assert_eq!(actual.out, "[1, 2]");
@@ -55,7 +55,7 @@ fn filters_with_1_arity_block() {
 fn unique_env_each_iteration() {
     let actual = nu!(
         cwd: "tests/fixtures/formats",
-        "[1 2] | where { print ($env.PWD | str ends-with 'formats') | cd '/' | true } | to nuon"
+        "[1 2] | where {|| print ($env.PWD | str ends-with 'formats') | cd '/' | true } | to nuon"
     );
 
     assert_eq!(actual.out, "truetrue[1, 2]");

crates/nu-parser/src/errors.rs

@@ -38,6 +38,13 @@ pub enum ParseError {
     #[diagnostic(code(nu::parser::parse_mismatch))]
     Expected(String, #[label("expected {0}")] Span),
 
+    #[error("Missing || inside closure")]
+    #[diagnostic(
+        code(nu::parser::closure_missing_pipe),
+        help("Try add || to the beginning of closure")
+    )]
+    ClosureMissingPipe(#[label("Parsing as a closure, but || is missing")] Span),
+
     #[error("Type mismatch during operation.")]
     #[diagnostic(code(nu::parser::type_mismatch))]
     Mismatch(String, String, #[label("expected {0}, found {1}")] Span), // expected, found, span
@@ -487,6 +494,7 @@ impl ParseError {
             ParseError::UnknownOperator(_, _, s) => *s,
             ParseError::InvalidLiteral(_, _, s) => *s,
             ParseError::NotAConstant(s) => *s,
+            ParseError::ClosureMissingPipe(s) => *s,
         }
     }
 }

crates/nu-parser/src/parser.rs

@@ -1779,8 +1779,10 @@ pub fn parse_brace_expr(
 
     if matches!(second_token, None) {
         // If we're empty, that means an empty record or closure
-        if matches!(shape, SyntaxShape::Closure(_)) {
-            parse_closure_expression(working_set, shape, span, expand_aliases_denylist)
+        if matches!(shape, SyntaxShape::Closure(None)) {
+            parse_closure_expression(working_set, shape, span, expand_aliases_denylist, false)
+        } else if matches!(shape, SyntaxShape::Closure(Some(_))) {
+            parse_closure_expression(working_set, shape, span, expand_aliases_denylist, true)
         } else if matches!(shape, SyntaxShape::Block) {
             parse_block_expression(working_set, span, expand_aliases_denylist)
         } else {
@@ -1789,11 +1791,13 @@ pub fn parse_brace_expr(
     } else if matches!(second_token_contents, Some(TokenContents::Pipe))
         || matches!(second_token_contents, Some(TokenContents::PipePipe))
     {
-        parse_closure_expression(working_set, shape, span, expand_aliases_denylist)
+        parse_closure_expression(working_set, shape, span, expand_aliases_denylist, true)
     } else if matches!(third_token, Some(b":")) {
         parse_full_cell_path(working_set, None, span, expand_aliases_denylist)
-    } else if matches!(shape, SyntaxShape::Closure(_)) || matches!(shape, SyntaxShape::Any) {
-        parse_closure_expression(working_set, shape, span, expand_aliases_denylist)
+    } else if matches!(shape, SyntaxShape::Closure(None)) {
+        parse_closure_expression(working_set, shape, span, expand_aliases_denylist, false)
+    } else if matches!(shape, SyntaxShape::Closure(Some(_))) || matches!(shape, SyntaxShape::Any) {
+        parse_closure_expression(working_set, shape, span, expand_aliases_denylist, true)
     } else if matches!(shape, SyntaxShape::Block) {
         parse_block_expression(working_set, span, expand_aliases_denylist)
     } else {
@@ -4414,6 +4418,7 @@ pub fn parse_closure_expression(
     shape: &SyntaxShape,
     span: Span,
     expand_aliases_denylist: &[usize],
+    require_pipe: bool,
 ) -> (Expression, Option<ParseError>) {
     trace!("parsing: closure expression");
 
@@ -4490,7 +4495,15 @@ pub fn parse_closure_expression(
             Some((Box::new(Signature::new("closure".to_string())), *span)),
             1,
         ),
-        _ => (None, 0),
+        _ => {
+            if require_pipe {
+                error = error.or(Some(ParseError::ClosureMissingPipe(span)));
+                working_set.exit_scope();
+                return (garbage(span), error);
+            } else {
+                (None, 0)
+            }
+        }
     };
 
     // TODO: Finish this

crates/nu-parser/tests/test_parser.rs

@@ -1563,7 +1563,13 @@ mod input_types {
                 )
                 .optional(
                     "else_expression",
-                    SyntaxShape::Keyword(b"else".to_vec(), Box::new(SyntaxShape::Expression)),
+                    SyntaxShape::Keyword(
+                        b"else".to_vec(),
+                        Box::new(SyntaxShape::OneOf(vec![
+                            SyntaxShape::Block,
+                            SyntaxShape::Expression,
+                        ])),
+                    ),
                     "expression or block to run if check fails",
                 )
                 .category(Category::Core)