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Fix and optimize visit_target usage #510

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merged 6 commits into from
Jul 5, 2021
Merged

Fix and optimize visit_target usage #510

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cb21778
Prepare generator::visit_target() for nested targets
Kijewski Jul 1, 2021
072077e
Remove duplicated code in generator
Kijewski Jul 1, 2021
02521c8
Remove needless deref, only to ref it a few lines down
Kijewski Jul 1, 2021
ad3ddf0
Move logic where target shadows or declares a variable into method
Kijewski Jul 1, 2021
0b095fb
Reduce code duplication for writing targets
Kijewski Jul 1, 2021
f31d973
Add loop variable shadowing test
Kijewski Jul 1, 2021
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80 changes: 36 additions & 44 deletions askama_shared/src/generator.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -807,24 +807,27 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
self.handle_ws(ws);
self.write_buf_writable(buf)?;
buf.write("let ");
match *var {
self.visit_target(buf, var);
buf.writeln(";")
}

fn is_shadowing_variable(&self, var: &Target<'a>) -> bool {
match var {
Target::Name(name) => {
let name = normalize_identifier(name);
self.locals.insert_with_default(name);
buf.write(name);
}
Target::Tuple(ref targets) => {
buf.write("(");
for name in targets {
let name = normalize_identifier(name);
self.locals.insert_with_default(name);
buf.write(name);
buf.write(",");
match self.locals.get(&name) {
// declares a new variable
None => false,
// an initialized variable gets shadowed
Some(meta) if meta.initialized => true,
// initializes a variable that was introduced in a LetDecl before
_ => false,
}
buf.write(")");
}
Target::Tuple(targets) => targets
.iter()
.any(|name| self.is_shadowing_variable(&Target::Name(name))),
}
buf.writeln(";")
}

fn write_let(
Expand All @@ -838,36 +841,27 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
let mut expr_buf = Buffer::new(0);
self.visit_expr(&mut expr_buf, val)?;

match *var {
let shadowed = self.is_shadowing_variable(var);
if shadowed {
// Need to flush the buffer if the variable is being shadowed,
// to ensure the old variable is used.
self.write_buf_writable(buf)?;
}
if shadowed
|| !matches!(var, &Target::Name(_))
|| matches!(var, Target::Name(name) if self.locals.get(name).is_none())
{
buf.write("let ");
}

match var {
Target::Name(name) => {
let name = normalize_identifier(name);
let meta = self.locals.get(&name).cloned();

let shadowed = matches!(&meta, Some(meta) if meta.initialized);
if shadowed {
// Need to flush the buffer if the variable is being shadowed,
// to ensure the old variable is used.
self.write_buf_writable(buf)?;
}
if shadowed || meta.is_none() {
buf.write("let ");
}
buf.write(name);

self.locals.insert(name, LocalMeta::initialized());
}
Target::Tuple(ref targets) => {
let shadowed = targets.iter().any(|name| {
let name = normalize_identifier(name);
matches!(self.locals.get(&name), Some(meta) if meta.initialized)
});
if shadowed {
// Need to flush the buffer if the variable is being shadowed,
// to ensure the old variable is used.
self.write_buf_writable(buf)?;
}

buf.write("let (");
Target::Tuple(targets) => {
buf.write("(");
for name in targets {
let name = normalize_identifier(name);
self.locals.insert(name, LocalMeta::initialized());
Expand Down Expand Up @@ -1533,19 +1527,17 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
DisplayWrap::Unwrapped
}

fn visit_target(&mut self, buf: &mut Buffer, target: &'a Target<'_>) {
match *target {
fn visit_target(&mut self, buf: &mut Buffer, target: &Target<'a>) {
match target {
Target::Name(name) => {
let name = normalize_identifier(name);
self.locals.insert_with_default(name);
buf.write(name);
}
Target::Tuple(ref targets) => {
Target::Tuple(targets) => {
buf.write("(");
for name in targets {
let name = normalize_identifier(name);
self.locals.insert_with_default(name);
buf.write(name);
self.visit_target(buf, &Target::Name(name));
buf.write(",");
}
buf.write(")");
Expand Down