Suite formatting and JoinNodesBuilder (#4805)

crates/ruff_python_formatter/src/builders.rs

@@ -0,0 +1,212 @@
+use crate::context::NodeLevel;
+use crate::prelude::*;
+use crate::trivia::lines_before;
+use ruff_formatter::write;
+use rustpython_parser::ast::Ranged;
+
+/// Provides Python specific extensions to [`Formatter`].
+pub(crate) trait PyFormatterExtensions<'ast, 'buf> {
+    /// Creates a joiner that inserts the appropriate number of empty lines between two nodes, depending on the
+    /// line breaks that separate the two nodes in the source document. The `level` customizes the maximum allowed
+    /// empty lines between any two nodes. Separates any two nodes by at least a hard line break.
+    ///
+    /// * [`NodeLevel::Module`]: Up to two empty lines
+    /// * [`NodeLevel::Statement`]: Up to one empty line
+    /// * [`NodeLevel::Parenthesized`]: No empty lines
+    fn join_nodes<'fmt>(&'fmt mut self, level: NodeLevel) -> JoinNodesBuilder<'fmt, 'ast, 'buf>;
+}
+
+impl<'buf, 'ast> PyFormatterExtensions<'ast, 'buf> for PyFormatter<'ast, 'buf> {
+    fn join_nodes<'fmt>(&'fmt mut self, level: NodeLevel) -> JoinNodesBuilder<'fmt, 'ast, 'buf> {
+        JoinNodesBuilder::new(self, level)
+    }
+}
+
+#[must_use = "must eventually call `finish()` on the builder."]
+pub(crate) struct JoinNodesBuilder<'fmt, 'ast, 'buf> {
+    fmt: &'fmt mut PyFormatter<'ast, 'buf>,
+    result: FormatResult<()>,
+    has_elements: bool,
+    node_level: NodeLevel,
+}
+
+impl<'fmt, 'ast, 'buf> JoinNodesBuilder<'fmt, 'ast, 'buf> {
+    fn new(fmt: &'fmt mut PyFormatter<'ast, 'buf>, level: NodeLevel) -> Self {
+        Self {
+            fmt,
+            result: Ok(()),
+            has_elements: false,
+            node_level: level,
+        }
+    }
+
+    /// Writes a `node`, inserting the appropriate number of line breaks depending on the number of
+    /// line breaks that were present in the source document. Uses `content` to format the `node`.
+    pub(crate) fn entry<T>(&mut self, node: &T, content: &dyn Format<PyFormatContext<'ast>>)
+    where
+        T: Ranged,
+    {
+        let node_level = self.node_level;
+        let separator = format_with(|f: &mut PyFormatter| match node_level {
+            NodeLevel::TopLevel => match lines_before(f.context().contents(), node.start()) {
+                0 | 1 => hard_line_break().fmt(f),
+                2 => empty_line().fmt(f),
+                _ => write!(f, [empty_line(), empty_line()]),
+            },
+            NodeLevel::Statement => match lines_before(f.context().contents(), node.start()) {
+                0 | 1 => hard_line_break().fmt(f),
+                _ => empty_line().fmt(f),
+            },
+            NodeLevel::Parenthesized => hard_line_break().fmt(f),
+        });
+
+        self.entry_with_separator(&separator, content);
+    }
+
+    /// Writes a sequence of node with their content tuples, inserting the appropriate number of line breaks between any two of them
+    /// depending on the number of line breaks that exist in the source document.
+    #[allow(unused)]
+    pub(crate) fn entries<T, F, I>(&mut self, entries: I) -> &mut Self
+    where
+        T: Ranged,
+        F: Format<PyFormatContext<'ast>>,
+        I: IntoIterator<Item = (T, F)>,
+    {
+        for (node, content) in entries {
+            self.entry(&node, &content);
+        }
+
+        self
+    }
+
+    /// Writes a sequence of nodes, using their [`AsFormat`] implementation to format the content.
+    /// Inserts the appropriate number of line breaks between any two nodes, depending on the number of
+    /// line breaks in the source document.
+    #[allow(unused)]
+    pub(crate) fn nodes<'a, T, I>(&mut self, nodes: I) -> &mut Self
+    where
+        T: Ranged + AsFormat<PyFormatContext<'ast>> + 'a,
+        I: IntoIterator<Item = &'a T>,
+    {
+        for node in nodes {
+            self.entry(node, &node.format());
+        }
+
+        self
+    }
+
+    /// Writes a single entry using the specified separator to separate the entry from a previous entry.
+    pub(crate) fn entry_with_separator(
+        &mut self,
+        separator: &dyn Format<PyFormatContext<'ast>>,
+        content: &dyn Format<PyFormatContext<'ast>>,
+    ) {
+        self.result = self.result.and_then(|_| {
+            if self.has_elements {
+                separator.fmt(self.fmt)?;
+            }
+
+            self.has_elements = true;
+
+            content.fmt(self.fmt)
+        });
+    }
+
+    /// Finishes the joiner and gets the format result.
+    pub(crate) fn finish(&mut self) -> FormatResult<()> {
+        self.result
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::comments::Comments;
+    use crate::context::{NodeLevel, PyFormatContext};
+    use crate::prelude::*;
+    use ruff_formatter::format;
+    use ruff_formatter::SimpleFormatOptions;
+    use rustpython_parser::ast::ModModule;
+    use rustpython_parser::Parse;
+
+    fn format_ranged(level: NodeLevel) -> String {
+        let source = r#"
+a = 10
+
+
+
+three_leading_newlines = 80
+
+
+two_leading_newlines = 20
+
+one_leading_newline = 10
+no_leading_newline = 30
+"#;
+
+        let module = ModModule::parse(source, "test.py").unwrap();
+
+        let context =
+            PyFormatContext::new(SimpleFormatOptions::default(), source, Comments::default());
+
+        let test_formatter =
+            format_with(|f: &mut PyFormatter| f.join_nodes(level).nodes(&module.body).finish());
+
+        let formatted = format!(context, [test_formatter]).unwrap();
+        let printed = formatted.print().unwrap();
+
+        printed.as_code().to_string()
+    }
+
+    // Keeps up to two empty lines
+    #[test]
+    fn ranged_builder_top_level() {
+        let printed = format_ranged(NodeLevel::TopLevel);
+
+        assert_eq!(
+            &printed,
+            r#"a = 10
+
+
+three_leading_newlines = 80
+
+
+two_leading_newlines = 20
+
+one_leading_newline = 10
+no_leading_newline = 30"#
+        );
+    }
+
+    // Should keep at most one empty level
+    #[test]
+    fn ranged_builder_statement_level() {
+        let printed = format_ranged(NodeLevel::Statement);
+
+        assert_eq!(
+            &printed,
+            r#"a = 10
+
+three_leading_newlines = 80
+
+two_leading_newlines = 20
+
+one_leading_newline = 10
+no_leading_newline = 30"#
+        );
+    }
+
+    // Removes all empty lines
+    #[test]
+    fn ranged_builder_parenthesized_level() {
+        let printed = format_ranged(NodeLevel::Parenthesized);
+
+        assert_eq!(
+            &printed,
+            r#"a = 10
+three_leading_newlines = 80
+two_leading_newlines = 20
+one_leading_newline = 10
+no_leading_newline = 30"#
+        );
+    }
+}