python_ast/ast/tree/
for_stmt.rs

1use proc_macro2::TokenStream;
2use pyo3::{Borrowed, FromPyObject, PyAny, PyResult, types::PyAnyMethods};
3use quote::quote;
4use serde::{Deserialize, Serialize};
5
6use crate::{
7    CodeGen, CodeGenContext, ExprType, PythonOptions, SymbolTableScopes,
8    Node, impl_node_with_positions, PyAttributeExtractor, extract_list
9};
10
11use super::Statement;
12
13#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
14pub struct For {
15    pub target: ExprType,
16    pub iter: ExprType,
17    pub body: Vec<Statement>,
18    pub orelse: Vec<Statement>,
19    pub lineno: Option<usize>,
20    pub col_offset: Option<usize>,
21    pub end_lineno: Option<usize>,
22    pub end_col_offset: Option<usize>,
23}
24
25impl<'a, 'py> FromPyObject<'a, 'py> for For {
26    type Error = pyo3::PyErr;
27    fn extract(ob: Borrowed<'a, 'py, PyAny>) -> PyResult<Self> {
28        let target = ob.extract_attr_with_context("target", "for loop target")?;
29        let iter = ob.extract_attr_with_context("iter", "for loop iterator")?;
30        
31        let target = target
32            .extract()
33            .map_err(|e| crate::extraction_failure("for loop target", &ob, e))?;
34        let iter = iter
35            .extract()
36            .map_err(|e| crate::extraction_failure("for loop iterator", &ob, e))?;
37        
38        let body: Vec<Statement> = extract_list(&ob, "body", "for body statements")?;
39        let orelse: Vec<Statement> = extract_list(&ob, "orelse", "for else statements")?;
40        
41        Ok(For {
42            target,
43            iter,
44            body,
45            orelse,
46            lineno: ob.lineno(),
47            col_offset: ob.col_offset(),
48            end_lineno: ob.end_lineno(),
49            end_col_offset: ob.end_col_offset(),
50        })
51    }
52}
53
54impl_node_with_positions!(For { lineno, col_offset, end_lineno, end_col_offset });
55
56impl CodeGen for For {
57    type Context = CodeGenContext;
58    type Options = PythonOptions;
59    type SymbolTable = SymbolTableScopes;
60
61    fn find_symbols(self, symbols: Self::SymbolTable) -> Self::SymbolTable {
62        let symbols = self.target.find_symbols(symbols);
63        let symbols = self.iter.find_symbols(symbols);
64        let symbols = self.body.into_iter().fold(symbols, |acc, stmt| stmt.find_symbols(acc));
65        self.orelse.into_iter().fold(symbols, |acc, stmt| stmt.find_symbols(acc))
66    }
67
68    fn to_rust(
69        self,
70        ctx: Self::Context,
71        options: Self::Options,
72        symbols: Self::SymbolTable,
73    ) -> Result<TokenStream, Box<dyn std::error::Error>> {
74        let target = self.target.to_rust(ctx.clone(), options.clone(), symbols.clone())?;
75        let iter = self.iter.to_rust(ctx.clone(), options.clone(), symbols.clone())?;
76
77        let has_else = !self.orelse.is_empty();
78        // Break-tracking is only needed when the else clause could be skipped
79        // by a break belonging to this loop; otherwise the flag would be
80        // declared mutable but never written.
81        let tracks_break = has_else && crate::loop_body_has_direct_break(&self.body);
82        // Body statements compile inside a Loop context so `break` can honor
83        // the else clause; the else clause itself is outside the loop.
84        let body_ctx = crate::CodeGenContext::Loop {
85            has_else: tracks_break,
86            parent: Box::new(ctx.clone()),
87        };
88        let body_stmts: Result<Vec<_>, _> = self.body
89            .into_iter()
90            .map(|stmt| stmt.to_rust(body_ctx.clone(), options.clone(), symbols.clone()))
91            .collect();
92        let body_stmts = body_stmts?;
93
94        if !has_else {
95            Ok(quote! {
96                for #target in #iter {
97                    #(#body_stmts;)*
98                }
99            })
100        } else {
101            // Python's for/else: the else clause runs iff the loop finished
102            // without hitting `break` (which sets __rython_broke).
103            let else_stmts: Result<Vec<_>, _> = self.orelse
104                .into_iter()
105                .map(|stmt| stmt.to_rust(ctx.clone(), options.clone(), symbols.clone()))
106                .collect();
107            let else_stmts = else_stmts?;
108
109            if tracks_break {
110                Ok(quote! {
111                    {
112                        let mut __rython_broke = false;
113                        for #target in #iter {
114                            #(#body_stmts;)*
115                        }
116                        if !__rython_broke {
117                            #(#else_stmts;)*
118                        }
119                    }
120                })
121            } else {
122                // No break can skip the else clause; run it unconditionally.
123                Ok(quote! {
124                    {
125                        for #target in #iter {
126                            #(#body_stmts;)*
127                        }
128                        #(#else_stmts;)*
129                    }
130                })
131            }
132        }
133    }
134}
135
136#[cfg(test)]
137mod tests {
138    use super::*;
139    use crate::create_parse_test;
140
141    create_parse_test!(test_simple_for, "for x in range(10):\n    print(x)", "for_test.py");
142    create_parse_test!(test_for_else, "for x in range(10):\n    print(x)\nelse:\n    print('done')", "for_test.py");
143    create_parse_test!(test_for_list, "for item in [1, 2, 3]:\n    print(item)", "for_test.py");
144}
python_ast/ast/tree/for_stmt.rs

python_ast/ast/tree/
for_stmt.rs
