fix: context-aware named param conversion (#513)

we were blindly converting named parameters to positional parameters.
but the latter is only valid as a literal, and not as an identifier.

statements like

```sql
grant usage on schema public, app_public, app_hidden to :DB_ROLE;
```

are not valid when converted to

```sql
grant usage on schema public, app_public, app_hidden to $1;
```

i went a bit back and forth on this and decided the easiest way to fix
this is to convert to identifiers like `a` if the previous non-trivia
token is one of a set list of tokens. We will probably have a bunch of
edge cases here but fixing them should be as easy as adding a keyword to
the list.

now, we convert to

```sql
grant usage on schema public, app_public, app_hidden to a;
```

closes #510

Author: psteinroe

crates/pgt_lexer/src/lexer.rs

@@ -143,7 +143,7 @@ impl<'a> Lexer<'a> {
                         }
                         _ => {}
                     };
-                    SyntaxKind::POSITIONAL_PARAM
+                    SyntaxKind::NAMED_PARAM
                 }
                 pgt_tokenizer::TokenKind::QuotedIdent { terminated } => {
                     if !terminated {

crates/pgt_lexer_codegen/src/syntax_kind.rs

@@ -65,6 +65,9 @@ pub fn syntax_kind_mod() -> proc_macro2::TokenStream {
 
     let mut enum_variants: Vec<TokenStream> = Vec::new();
     let mut from_kw_match_arms: Vec<TokenStream> = Vec::new();
+    let mut is_kw_match_arms: Vec<TokenStream> = Vec::new();
+
+    let mut is_trivia_match_arms: Vec<TokenStream> = Vec::new();
 
     // collect keywords
     for kw in &all_keywords {
@@ -78,18 +81,30 @@ pub fn syntax_kind_mod() -> proc_macro2::TokenStream {
         from_kw_match_arms.push(quote! {
             #kw => Some(SyntaxKind::#kind_ident)
         });
+        is_kw_match_arms.push(quote! {
+            SyntaxKind::#kind_ident => true
+        });
     }
 
     // collect extra keywords
     EXTRA.iter().for_each(|&name| {
         let variant_name = format_ident!("{}", name);
         enum_variants.push(quote! { #variant_name });
+
+        if name == "COMMENT" {
+            is_trivia_match_arms.push(quote! {
+                SyntaxKind::#variant_name => true
+            });
+        }
     });
 
     // collect whitespace variants
     WHITESPACE.iter().for_each(|&name| {
         let variant_name = format_ident!("{}", name);
         enum_variants.push(quote! { #variant_name });
+        is_trivia_match_arms.push(quote! {
+            SyntaxKind::#variant_name => true
+        });
     });
 
     // collect punctuations
@@ -119,6 +134,20 @@ pub fn syntax_kind_mod() -> proc_macro2::TokenStream {
                     _ => None
                 }
             }
+
+            pub fn is_keyword(&self) -> bool {
+                match self {
+                    #(#is_kw_match_arms),*,
+                    _ => false
+                }
+            }
+
+            pub fn is_trivia(&self) -> bool {
+                match self {
+                    #(#is_trivia_match_arms),*,
+                    _ => false
+                }
+            }
         }
     }
 }

crates/pgt_tokenizer/src/lib.rs

@@ -668,6 +668,13 @@ mod tests {
         assert_debug_snapshot!(result);
     }
 
+    #[test]
+    fn graphile_named_param() {
+        let result =
+            lex("grant usage on schema public, app_public, app_hidden to :DATABASE_VISITOR;");
+        assert_debug_snapshot!(result);
+    }
+
     #[test]
     fn named_param_dollar_raw() {
         let result = lex("select 1 from c where id = $id;");

crates/pgt_tokenizer/src/snapshots/pgt_tokenizer__tests__graphile_named_param.snap

@@ -0,0 +1,27 @@
+---
+source: crates/pgt_tokenizer/src/lib.rs
+expression: result
+snapshot_kind: text
+---
+[
+    "grant" @ Ident,
+    " " @ Space,
+    "usage" @ Ident,
+    " " @ Space,
+    "on" @ Ident,
+    " " @ Space,
+    "schema" @ Ident,
+    " " @ Space,
+    "public" @ Ident,
+    "," @ Comma,
+    " " @ Space,
+    "app_public" @ Ident,
+    "," @ Comma,
+    " " @ Space,
+    "app_hidden" @ Ident,
+    " " @ Space,
+    "to" @ Ident,
+    " " @ Space,
+    ":DATABASE_VISITOR" @ NamedParam { kind: ColonRaw },
+    ";" @ Semi,
+]

crates/pgt_workspace/src/workspace/server/pg_query.rs

@@ -3,9 +3,9 @@ use std::num::NonZeroUsize;
 use std::sync::{Arc, LazyLock, Mutex};
 
 use lru::LruCache;
+use pgt_lexer::lex;
 use pgt_query_ext::diagnostics::*;
 use pgt_text_size::TextRange;
-use pgt_tokenizer::tokenize;
 use regex::Regex;
 
 use super::statement_identifier::StatementId;
@@ -104,6 +104,27 @@ fn is_composite_type_error(err: &str) -> bool {
     COMPOSITE_TYPE_ERROR_RE.is_match(err)
 }
 
+// Keywords that, when preceding a named parameter, indicate that the parameter should be treated
+// as an identifier rather than a positional parameter.
+const IDENTIFIER_CONTEXT: [pgt_lexer::SyntaxKind; 15] = [
+    pgt_lexer::SyntaxKind::TO_KW,
+    pgt_lexer::SyntaxKind::FROM_KW,
+    pgt_lexer::SyntaxKind::SCHEMA_KW,
+    pgt_lexer::SyntaxKind::TABLE_KW,
+    pgt_lexer::SyntaxKind::INDEX_KW,
+    pgt_lexer::SyntaxKind::CONSTRAINT_KW,
+    pgt_lexer::SyntaxKind::OWNER_KW,
+    pgt_lexer::SyntaxKind::ROLE_KW,
+    pgt_lexer::SyntaxKind::USER_KW,
+    pgt_lexer::SyntaxKind::DATABASE_KW,
+    pgt_lexer::SyntaxKind::TYPE_KW,
+    pgt_lexer::SyntaxKind::CAST_KW,
+    pgt_lexer::SyntaxKind::ALTER_KW,
+    pgt_lexer::SyntaxKind::DROP_KW,
+    // for schema.table style identifiers
+    pgt_lexer::SyntaxKind::DOT,
+];
+
 /// Converts named parameters in a SQL query string to positional parameters.
 ///
 /// This function scans the input SQL string for named parameters (e.g., `@param`, `:param`, `:'param'`)
@@ -116,13 +137,16 @@ pub fn convert_to_positional_params(text: &str) -> String {
     let mut result = String::with_capacity(text.len());
     let mut param_mapping: HashMap<&str, usize> = HashMap::new();
     let mut param_index = 1;
-    let mut position = 0;
 
-    for token in tokenize(text) {
-        let token_len = token.len as usize;
-        let token_text = &text[position..position + token_len];
+    let lexed = lex(text);
+    for (token_idx, kind) in lexed.tokens().enumerate() {
+        if kind == pgt_lexer::SyntaxKind::EOF {
+            break;
+        }
+
+        let token_text = lexed.text(token_idx);
 
-        if matches!(token.kind, pgt_tokenizer::TokenKind::NamedParam { .. }) {
+        if matches!(kind, pgt_lexer::SyntaxKind::NAMED_PARAM) {
             let idx = match param_mapping.get(token_text) {
                 Some(&index) => index,
                 None => {
@@ -133,7 +157,16 @@ pub fn convert_to_positional_params(text: &str) -> String {
                 }
             };
 
-            let replacement = format!("${}", idx);
+            // find previous non-trivia token
+            let prev_token = (0..token_idx)
+                .rev()
+                .map(|i| lexed.kind(i))
+                .find(|kind| !kind.is_trivia());
+
+            let replacement = match prev_token {
+                Some(k) if IDENTIFIER_CONTEXT.contains(&k) => deterministic_identifier(idx - 1),
+                _ => format!("${}", idx),
+            };
             let original_len = token_text.len();
             let replacement_len = replacement.len();
 
@@ -146,17 +179,45 @@ pub fn convert_to_positional_params(text: &str) -> String {
         } else {
             result.push_str(token_text);
         }
-
-        position += token_len;
     }
 
     result
 }
 
+const ALPHABET: [char; 26] = [
+    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
+    't', 'u', 'v', 'w', 'x', 'y', 'z',
+];
+
+/// Generates a deterministic identifier based on the given index.
+fn deterministic_identifier(idx: usize) -> String {
+    let iteration = idx / ALPHABET.len();
+    let pos = idx % ALPHABET.len();
+
+    format!(
+        "{}{}",
+        ALPHABET[pos],
+        if iteration > 0 {
+            deterministic_identifier(iteration - 1)
+        } else {
+            "".to_string()
+        }
+    )
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    #[test]
+    fn test_deterministic_identifier() {
+        assert_eq!(deterministic_identifier(0), "a");
+        assert_eq!(deterministic_identifier(25), "z");
+        assert_eq!(deterministic_identifier(26), "aa");
+        assert_eq!(deterministic_identifier(27), "ba");
+        assert_eq!(deterministic_identifier(51), "za");
+    }
+
     #[test]
     fn test_convert_to_positional_params() {
         let input = "select * from users where id = @one and name = :two and email = :'three';";
@@ -177,6 +238,24 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_positional_params_in_grant() {
+        let input = "grant usage on schema public, app_public, app_hidden to :DB_ROLE;";
+
+        let result = convert_to_positional_params(input);
+
+        assert_eq!(
+            result,
+            "grant usage on schema public, app_public, app_hidden to a       ;"
+        );
+
+        let store = PgQueryStore::new();
+
+        let res = store.get_or_cache_ast(&StatementId::new(input));
+
+        assert!(res.is_ok());
+    }
+
     #[test]
     fn test_plpgsql_syntax_error() {
         let input = "