SSR: Parse template as Rust code.

This is in preparation for a subsequent commit where we add special
handling for paths in the template, allowing them to be qualified
differently in different contexts.

5 files changed, 112 insertions, 82 deletions

diff --git a/crates/ra_ssr/src/lib.rs b/crates/ra_ssr/src/lib.rs
index 3009dcb93..b28913a65 100644
--- a/crates/ra_ssr/src/lib.rs
+++ b/crates/ra_ssr/src/lib.rs
@@ -15,7 +15,6 @@ pub use crate::errors::SsrError;
 pub use crate::matching::Match;
 use crate::matching::MatchFailureReason;
 use hir::Semantics;
-use parsing::SsrTemplate;
 use ra_db::{FileId, FileRange};
 use ra_syntax::{ast, AstNode, SyntaxNode, TextRange};
 use ra_text_edit::TextEdit;
@@ -26,7 +25,7 @@ pub struct SsrRule {
     /// A structured pattern that we're searching for.
     pattern: parsing::RawPattern,
     /// What we'll replace it with.
-    template: SsrTemplate,
+    template: parsing::RawPattern,
     parsed_rules: Vec<parsing::ParsedRule>,
 }
 
@@ -72,7 +71,11 @@ impl<'db> MatchFinder<'db> {
             None
         } else {
             use ra_db::SourceDatabaseExt;
-            Some(replacing::matches_to_edit(&matches, &self.sema.db.file_text(file_id)))
+            Some(replacing::matches_to_edit(
+                &matches,
+                &self.sema.db.file_text(file_id),
+                &self.rules,
+            ))
         }
     }
 
@@ -111,9 +114,8 @@ impl<'db> MatchFinder<'db> {
     }
 
     fn add_parsed_rules(&mut self, parsed_rules: Vec<parsing::ParsedRule>) {
-        // FIXME: This doesn't need to be a for loop, but does in a subsequent commit. Justify it
-        // being a for-loop.
-        for parsed_rule in parsed_rules {
+        for mut parsed_rule in parsed_rules {
+            parsed_rule.index = self.rules.len();
             self.rules.push(parsed_rule);
         }
     }
diff --git a/crates/ra_ssr/src/matching.rs b/crates/ra_ssr/src/matching.rs
index 842f4b6f3..486191635 100644
--- a/crates/ra_ssr/src/matching.rs
+++ b/crates/ra_ssr/src/matching.rs
@@ -2,7 +2,7 @@
 //! process of matching, placeholder values are recorded.
 
 use crate::{
-    parsing::{Constraint, NodeKind, ParsedRule, Placeholder, SsrTemplate},
+    parsing::{Constraint, NodeKind, ParsedRule, Placeholder},
     SsrMatches,
 };
 use hir::Semantics;
@@ -48,9 +48,7 @@ pub struct Match {
     pub(crate) matched_node: SyntaxNode,
     pub(crate) placeholder_values: FxHashMap<Var, PlaceholderMatch>,
     pub(crate) ignored_comments: Vec<ast::Comment>,
-    // A copy of the template for the rule that produced this match. We store this on the match for
-    // if/when we do replacement.
-    pub(crate) template: Option<SsrTemplate>,
+    pub(crate) rule_index: usize,
 }
 
 /// Represents a `$var` in an SSR query.
@@ -131,7 +129,7 @@ impl<'db, 'sema> Matcher<'db, 'sema> {
             matched_node: code.clone(),
             placeholder_values: FxHashMap::default(),
             ignored_comments: Vec::new(),
-            template: rule.template.clone(),
+            rule_index: rule.index,
         };
         // Second matching pass, where we record placeholder matches, ignored comments and maybe do
         // any other more expensive checks that we didn't want to do on the first pass.
@@ -591,7 +589,7 @@ mod tests {
             "1+2"
         );
 
-        let edit = crate::replacing::matches_to_edit(&matches, input);
+        let edit = crate::replacing::matches_to_edit(&matches, input, &match_finder.rules);
         let mut after = input.to_string();
         edit.apply(&mut after);
         assert_eq!(after, "fn foo() {} fn main() { bar(1+2); }");
diff --git a/crates/ra_ssr/src/parsing.rs b/crates/ra_ssr/src/parsing.rs
index 682b7011a..cf7fb517f 100644
--- a/crates/ra_ssr/src/parsing.rs
+++ b/crates/ra_ssr/src/parsing.rs
@@ -15,12 +15,8 @@ use std::str::FromStr;
 pub(crate) struct ParsedRule {
     pub(crate) placeholders_by_stand_in: FxHashMap<SmolStr, Placeholder>,
     pub(crate) pattern: SyntaxNode,
-    pub(crate) template: Option<SsrTemplate>,
-}
-
-#[derive(Clone, Debug)]
-pub(crate) struct SsrTemplate {
-    pub(crate) tokens: Vec<PatternElement>,
+    pub(crate) template: Option<SyntaxNode>,
+    pub(crate) index: usize,
 }
 
 #[derive(Debug)]
@@ -64,18 +60,23 @@ pub(crate) struct Token {
 impl ParsedRule {
     fn new(
         pattern: &RawPattern,
-        template: Option<&SsrTemplate>,
+        template: Option<&RawPattern>,
     ) -> Result<Vec<ParsedRule>, SsrError> {
         let raw_pattern = pattern.as_rust_code();
+        let raw_template = template.map(|t| t.as_rust_code());
+        let raw_template = raw_template.as_ref().map(|s| s.as_str());
         let mut builder = RuleBuilder {
             placeholders_by_stand_in: pattern.placeholders_by_stand_in(),
             rules: Vec::new(),
         };
-        builder.try_add(ast::Expr::parse(&raw_pattern), template);
-        builder.try_add(ast::TypeRef::parse(&raw_pattern), template);
-        builder.try_add(ast::ModuleItem::parse(&raw_pattern), template);
-        builder.try_add(ast::Path::parse(&raw_pattern), template);
-        builder.try_add(ast::Pat::parse(&raw_pattern), template);
+        builder.try_add(ast::Expr::parse(&raw_pattern), raw_template.map(ast::Expr::parse));
+        builder.try_add(ast::TypeRef::parse(&raw_pattern), raw_template.map(ast::TypeRef::parse));
+        builder.try_add(
+            ast::ModuleItem::parse(&raw_pattern),
+            raw_template.map(ast::ModuleItem::parse),
+        );
+        builder.try_add(ast::Path::parse(&raw_pattern), raw_template.map(ast::Path::parse));
+        builder.try_add(ast::Pat::parse(&raw_pattern), raw_template.map(ast::Pat::parse));
         builder.build()
     }
 }
@@ -86,12 +87,22 @@ struct RuleBuilder {
 }
 
 impl RuleBuilder {
-    fn try_add<T: AstNode>(&mut self, pattern: Result<T, ()>, template: Option<&SsrTemplate>) {
-        match pattern {
-            Ok(pattern) => self.rules.push(ParsedRule {
+    fn try_add<T: AstNode>(&mut self, pattern: Result<T, ()>, template: Option<Result<T, ()>>) {
+        match (pattern, template) {
+            (Ok(pattern), Some(Ok(template))) => self.rules.push(ParsedRule {
+                placeholders_by_stand_in: self.placeholders_by_stand_in.clone(),
+                pattern: pattern.syntax().clone(),
+                template: Some(template.syntax().clone()),
+                // For now we give the rule an index of 0. It's given a proper index when the rule
+                // is added to the SsrMatcher. Using an Option<usize>, instead would be slightly
+                // more correct, but we delete this field from ParsedRule in a subsequent commit.
+                index: 0,
+            }),
+            (Ok(pattern), None) => self.rules.push(ParsedRule {
                 placeholders_by_stand_in: self.placeholders_by_stand_in.clone(),
                 pattern: pattern.syntax().clone(),
-                template: template.cloned(),
+                template: None,
+                index: 0,
             }),
             _ => {}
         }
@@ -99,7 +110,7 @@ impl RuleBuilder {
 
     fn build(self) -> Result<Vec<ParsedRule>, SsrError> {
         if self.rules.is_empty() {
-            bail!("Pattern is not a valid Rust expression, type, item, path or pattern");
+            bail!("Not a valid Rust expression, type, item, path or pattern");
         }
         Ok(self.rules)
     }
@@ -179,21 +190,6 @@ impl FromStr for SsrPattern {
     }
 }
 
-impl FromStr for SsrTemplate {
-    type Err = SsrError;
-
-    fn from_str(pattern_str: &str) -> Result<SsrTemplate, SsrError> {
-        let tokens = parse_pattern(pattern_str)?;
-        // Validate that the template is a valid fragment of Rust code. We reuse the validation
-        // logic for search patterns since the only thing that differs is the error message.
-        if SsrPattern::from_str(pattern_str).is_err() {
-            bail!("Replacement is not a valid Rust expression, type, item, path or pattern");
-        }
-        // Our actual template needs to preserve whitespace, so we can't reuse `tokens`.
-        Ok(SsrTemplate { tokens })
-    }
-}
-
 /// Returns `pattern_str`, parsed as a search or replace pattern. If `remove_whitespace` is true,
 /// then any whitespace tokens will be removed, which we do for the search pattern, but not for the
 /// replace pattern.
diff --git a/crates/ra_ssr/src/replacing.rs b/crates/ra_ssr/src/replacing.rs
index 81f8634ba..f1c5bdf14 100644
--- a/crates/ra_ssr/src/replacing.rs
+++ b/crates/ra_ssr/src/replacing.rs
@@ -1,70 +1,104 @@
 //! Code for applying replacement templates for matches that have previously been found.
 
 use crate::matching::Var;
-use crate::parsing::PatternElement;
-use crate::{Match, SsrMatches};
+use crate::{parsing::ParsedRule, Match, SsrMatches};
 use ra_syntax::ast::AstToken;
-use ra_syntax::TextSize;
+use ra_syntax::{SyntaxElement, SyntaxNode, SyntaxToken, TextSize};
 use ra_text_edit::TextEdit;
 
 /// Returns a text edit that will replace each match in `matches` with its corresponding replacement
 /// template. Placeholders in the template will have been substituted with whatever they matched to
 /// in the original code.
-pub(crate) fn matches_to_edit(matches: &SsrMatches, file_src: &str) -> TextEdit {
-    matches_to_edit_at_offset(matches, file_src, 0.into())
+pub(crate) fn matches_to_edit(
+    matches: &SsrMatches,
+    file_src: &str,
+    rules: &[ParsedRule],
+) -> TextEdit {
+    matches_to_edit_at_offset(matches, file_src, 0.into(), rules)
 }
 
 fn matches_to_edit_at_offset(
     matches: &SsrMatches,
     file_src: &str,
     relative_start: TextSize,
+    rules: &[ParsedRule],
 ) -> TextEdit {
     let mut edit_builder = ra_text_edit::TextEditBuilder::default();
     for m in &matches.matches {
         edit_builder.replace(
             m.range.range.checked_sub(relative_start).unwrap(),
-            render_replace(m, file_src),
+            render_replace(m, file_src, rules),
         );
     }
     edit_builder.finish()
 }
 
-fn render_replace(match_info: &Match, file_src: &str) -> String {
+struct ReplacementRenderer<'a> {
+    match_info: &'a Match,
+    file_src: &'a str,
+    rules: &'a [ParsedRule],
+    rule: &'a ParsedRule,
+}
+
+fn render_replace(match_info: &Match, file_src: &str, rules: &[ParsedRule]) -> String {
     let mut out = String::new();
-    let template = match_info
+    let rule = &rules[match_info.rule_index];
+    let template = rule
         .template
         .as_ref()
         .expect("You called MatchFinder::edits after calling MatchFinder::add_search_pattern");
-    for r in &template.tokens {
-        match r {
-            PatternElement::Token(t) => out.push_str(t.text.as_str()),
-            PatternElement::Placeholder(p) => {
-                if let Some(placeholder_value) =
-                    match_info.placeholder_values.get(&Var(p.ident.to_string()))
-                {
-                    let range = &placeholder_value.range.range;
-                    let mut matched_text =
-                        file_src[usize::from(range.start())..usize::from(range.end())].to_owned();
-                    let edit = matches_to_edit_at_offset(
-                        &placeholder_value.inner_matches,
-                        file_src,
-                        range.start(),
-                    );
-                    edit.apply(&mut matched_text);
-                    out.push_str(&matched_text);
-                } else {
-                    // We validated that all placeholder references were valid before we
-                    // started, so this shouldn't happen.
-                    panic!(
-                        "Internal error: replacement referenced unknown placeholder {}",
-                        p.ident
-                    );
-                }
-            }
-        }
-    }
+    let renderer = ReplacementRenderer { match_info, file_src, rules, rule };
+    renderer.render_node_children(&template, &mut out);
     for comment in &match_info.ignored_comments {
         out.push_str(&comment.syntax().to_string());
     }
     out
 }
+
+impl ReplacementRenderer<'_> {
+    fn render_node_children(&self, node: &SyntaxNode, out: &mut String) {
+        for node_or_token in node.children_with_tokens() {
+            self.render_node_or_token(&node_or_token, out);
+        }
+    }
+
+    fn render_node_or_token(&self, node_or_token: &SyntaxElement, out: &mut String) {
+        match node_or_token {
+            SyntaxElement::Token(token) => {
+                self.render_token(&token, out);
+            }
+            SyntaxElement::Node(child_node) => {
+                self.render_node_children(&child_node, out);
+            }
+        }
+    }
+
+    fn render_token(&self, token: &SyntaxToken, out: &mut String) {
+        if let Some(placeholder) = self.rule.get_placeholder(&token) {
+            if let Some(placeholder_value) =
+                self.match_info.placeholder_values.get(&Var(placeholder.ident.to_string()))
+            {
+                let range = &placeholder_value.range.range;
+                let mut matched_text =
+                    self.file_src[usize::from(range.start())..usize::from(range.end())].to_owned();
+                let edit = matches_to_edit_at_offset(
+                    &placeholder_value.inner_matches,
+                    self.file_src,
+                    range.start(),
+                    self.rules,
+                );
+                edit.apply(&mut matched_text);
+                out.push_str(&matched_text);
+            } else {
+                // We validated that all placeholder references were valid before we
+                // started, so this shouldn't happen.
+                panic!(
+                    "Internal error: replacement referenced unknown placeholder {}",
+                    placeholder.ident
+                );
+            }
+        } else {
+            out.push_str(token.text().as_str());
+        }
+    }
+}
diff --git a/crates/ra_ssr/src/tests.rs b/crates/ra_ssr/src/tests.rs
index 9f5306592..1b03b7f4b 100644
--- a/crates/ra_ssr/src/tests.rs
+++ b/crates/ra_ssr/src/tests.rs
@@ -37,7 +37,7 @@ fn parser_repeated_name() {
 fn parser_invalid_pattern() {
     assert_eq!(
         parse_error_text(" ==>> ()"),
-        "Parse error: Pattern is not a valid Rust expression, type, item, path or pattern"
+        "Parse error: Not a valid Rust expression, type, item, path or pattern"
     );
 }
 
@@ -45,7 +45,7 @@ fn parser_invalid_pattern() {
 fn parser_invalid_template() {
     assert_eq!(
         parse_error_text("() ==>> )"),
-        "Parse error: Replacement is not a valid Rust expression, type, item, path or pattern"
+        "Parse error: Not a valid Rust expression, type, item, path or pattern"
     );
 }