Add operator completions (#13818)

# Description

This PR addresses #13676 . It adds completions for the operators listed
on https://www.nushell.sh/lang-guide/chapters/operators.html#operators
based on the type of the value before the cursor. Currently, values
created as the output of other operations will not have completions. For
example `(1 + 3)` will not have completions. When operators are
added/removed/updated the completions will have to be adjusted manually.

# User-Facing Changes
- Tab completions for operators

# Tests
Added unit tests to the new completion struct OperationCompletion for
int completions, float completions, and str completions

crates/nu-cli/src/completions/completer.rs

@@ -1,6 +1,6 @@
 use crate::completions::{
     CommandCompletion, Completer, CompletionOptions, CustomCompletion, DirectoryCompletion,
-    DotNuCompletion, FileCompletion, FlagCompletion, VariableCompletion,
+    DotNuCompletion, FileCompletion, FlagCompletion, OperatorCompletion, VariableCompletion,
 };
 use nu_color_config::{color_record_to_nustyle, lookup_ansi_color_style};
 use nu_engine::eval_block;
@@ -176,17 +176,32 @@ impl NuCompleter {
 
                         // Variables completion
                         if prefix.starts_with(b"$") || most_left_var.is_some() {
-                            let mut completer =
+                            let mut variable_names_completer =
                                 VariableCompletion::new(most_left_var.unwrap_or((vec![], vec![])));
 
-                            return self.process_completion(
-                                &mut completer,
+                            let mut variable_completions = self.process_completion(
+                                &mut variable_names_completer,
+                                &working_set,
+                                prefix.clone(),
+                                new_span,
+                                fake_offset,
+                                pos,
+                            );
+
+                            let mut variable_operations_completer =
+                                OperatorCompletion::new(pipeline_element.expr.clone());
+
+                            let mut variable_operations_completions = self.process_completion(
+                                &mut variable_operations_completer,
                                 &working_set,
                                 prefix,
                                 new_span,
                                 fake_offset,
                                 pos,
                             );
+
+                            variable_completions.append(&mut variable_operations_completions);
+                            return variable_completions;
                         }
 
                         // Flags completion
@@ -262,6 +277,26 @@ impl NuCompleter {
                                 } else if prev_expr_str == b"ls" {
                                     let mut completer = FileCompletion::new();
 
+                                    return self.process_completion(
+                                        &mut completer,
+                                        &working_set,
+                                        prefix,
+                                        new_span,
+                                        fake_offset,
+                                        pos,
+                                    );
+                                } else if matches!(
+                                    previous_expr.1,
+                                    FlatShape::Float
+                                        | FlatShape::Int
+                                        | FlatShape::String
+                                        | FlatShape::List
+                                        | FlatShape::Bool
+                                        | FlatShape::Variable(_)
+                                ) {
+                                    let mut completer =
+                                        OperatorCompletion::new(pipeline_element.expr.clone());
+
                                     return self.process_completion(
                                         &mut completer,
                                         &working_set,
@@ -533,6 +568,11 @@ mod completer_tests {
 
         let mut completer = NuCompleter::new(engine_state.into(), Arc::new(Stack::new()));
         let dataset = [
+            ("1 bit-sh", true, "b", vec!["bit-shl", "bit-shr"]),
+            ("1.0 bit-sh", false, "b", vec![]),
+            ("1 m", true, "m", vec!["mod"]),
+            ("1.0 m", true, "m", vec!["mod"]),
+            ("\"a\" s", true, "s", vec!["starts-with"]),
             ("sudo", false, "", Vec::new()),
             ("sudo l", true, "l", vec!["ls", "let", "lines", "loop"]),
             (" sudo", false, "", Vec::new()),

crates/nu-cli/src/completions/mod.rs

@@ -8,6 +8,7 @@ mod directory_completions;
 mod dotnu_completions;
 mod file_completions;
 mod flag_completions;
+mod operator_completions;
 mod variable_completions;
 
 pub use base::{Completer, SemanticSuggestion, SuggestionKind};
@@ -19,4 +20,5 @@ pub use directory_completions::DirectoryCompletion;
 pub use dotnu_completions::DotNuCompletion;
 pub use file_completions::{file_path_completion, matches, FileCompletion};
 pub use flag_completions::FlagCompletion;
+pub use operator_completions::OperatorCompletion;
 pub use variable_completions::VariableCompletion;

crates/nu-cli/src/completions/operator_completions.rs

@@ -0,0 +1,156 @@
+use crate::completions::{
+    Completer, CompletionOptions, MatchAlgorithm, SemanticSuggestion, SuggestionKind,
+};
+use nu_protocol::{
+    ast::{Expr, Expression},
+    engine::{Stack, StateWorkingSet},
+    Span, Type,
+};
+use reedline::Suggestion;
+
+#[derive(Clone)]
+pub struct OperatorCompletion {
+    previous_expr: Expression,
+}
+
+impl OperatorCompletion {
+    pub fn new(previous_expr: Expression) -> Self {
+        OperatorCompletion { previous_expr }
+    }
+}
+
+impl Completer for OperatorCompletion {
+    fn fetch(
+        &mut self,
+        working_set: &StateWorkingSet,
+        _stack: &Stack,
+        _prefix: Vec<u8>,
+        span: Span,
+        offset: usize,
+        _pos: usize,
+        _options: &CompletionOptions,
+    ) -> Vec<SemanticSuggestion> {
+        //Check if int, float, or string
+        let partial = std::str::from_utf8(working_set.get_span_contents(span)).unwrap_or("");
+        let op = match &self.previous_expr.expr {
+            Expr::BinaryOp(x, _, _) => &x.expr,
+            _ => {
+                return vec![];
+            }
+        };
+        let possible_operations = match op {
+            Expr::Int(_) => vec![
+                ("+", "Plus / Addition"),
+                ("-", "Minus / Subtraction"),
+                ("*", "Multiply"),
+                ("/", "Divide"),
+                ("==", "Equal"),
+                ("!=", "Not Equal"),
+                ("//", "Floor Division"),
+                ("<", "Less Than"),
+                (">", "Greater Than"),
+                ("<=", "Less Than or Equal to"),
+                (">=", "Greater Than or Equal to"),
+                ("mod", "Modulo"),
+                ("**", "Pow"),
+                ("bit-or", "bitwise or"),
+                ("bit-xor", "bitwise exclusive or"),
+                ("bit-and", "bitwise and"),
+                ("bit-shl", "bitwise shift left"),
+                ("bit-shr", "bitwise shift right"),
+            ],
+            Expr::String(_) => vec![
+                ("=~", "Regex Match / Contains"),
+                ("!~", "Not Regex Match / Not Contains"),
+                ("in", "In / Contains (doesn't use regex)"),
+                (
+                    "++",
+                    "Appends two lists, a list and a value, two strings, or two binary values",
+                ),
+                ("not-in", "Not In / Not Contains (doesn't use regex"),
+                ("starts-with", "Starts With"),
+                ("ends-with", "Ends With"),
+            ],
+            Expr::Float(_) => vec![
+                ("+", "Plus / Addition"),
+                ("-", "Minus / Subtraction"),
+                ("*", "Multiply"),
+                ("/", "Divide"),
+                ("==", "Equal"),
+                ("!=", "Not Equal"),
+                ("//", "Floor Division"),
+                ("<", "Less Than"),
+                (">", "Greater Than"),
+                ("<=", "Less Than or Equal to"),
+                (">=", "Greater Than or Equal to"),
+                ("mod", "Modulo"),
+                ("**", "Pow"),
+            ],
+            Expr::Bool(_) => vec![
+                ("and", "Checks if both values are true."),
+                ("or", "Checks if either value is true."),
+                ("xor", "Checks if one value is true and the other is false."),
+                ("not", "Negates a value or expression."),
+            ],
+            Expr::FullCellPath(path) => match path.head.expr {
+                Expr::List(_) => vec![(
+                    "++",
+                    "Appends two lists, a list and a value, two strings, or two binary values",
+                )],
+                Expr::Var(id) => get_variable_completions(id, working_set),
+                _ => vec![],
+            },
+            _ => vec![],
+        };
+
+        let match_algorithm = MatchAlgorithm::Prefix;
+        let input_fuzzy_search =
+            |(operator, _): &(&str, &str)| match_algorithm.matches_str(operator, partial);
+
+        possible_operations
+            .into_iter()
+            .filter(input_fuzzy_search)
+            .map(move |x| SemanticSuggestion {
+                suggestion: Suggestion {
+                    value: x.0.to_string(),
+                    description: Some(x.1.to_string()),
+                    span: reedline::Span::new(span.start - offset, span.end - offset),
+                    append_whitespace: true,
+                    ..Suggestion::default()
+                },
+                kind: Some(SuggestionKind::Command(
+                    nu_protocol::engine::CommandType::Builtin,
+                )),
+            })
+            .collect()
+    }
+}
+
+pub fn get_variable_completions<'a>(
+    id: nu_protocol::Id<nu_protocol::marker::Var>,
+    working_set: &StateWorkingSet,
+) -> Vec<(&'a str, &'a str)> {
+    let var = working_set.get_variable(id);
+    if !var.mutable {
+        return vec![];
+    }
+
+    match var.ty {
+        Type::List(_) | Type::String | Type::Binary => vec![
+            (
+                "++=",
+                "Appends a list, a value, a string, or a binary value to a variable.",
+            ),
+            ("=", "Assigns a value to a variable."),
+        ],
+
+        Type::Int | Type::Float => vec![
+            ("=", "Assigns a value to a variable."),
+            ("+=", "Adds a value to a variable."),
+            ("-=", "Subtracts a value from a variable."),
+            ("*=", "Multiplies a variable by a value"),
+            ("/=", "Divides a variable by a value."),
+        ],
+        _ => vec![],
+    }
+}