Experiment with multi-file schema handling in PSL (#4243)

* Implement multi-file schema handling in PSL

This commit implements multi-file schema handling in the Prisma Schema Language.

At a high level, instead of accepting a single string, `psl::validate_multi_file()` is an alternative to `psl::validate()` that accepts something morally equivalent to:

```json
{
  "./prisma/schema/a.prisma": "datasource db { ... }",
  "./prisma/schema/nested/b.prisma": "model Test { ... }"
}
```

There are tests for PSL validation with multiple schema files, but most of the rest of engines still consumes the single file version of `psl::validate()`. The implementation and the return type are shared between `psl::validate_multi_file()` and `psl::validate()`, so the change is completely transparent, other than the expectation of passing in a list of (file_name, file_contents) instead of a single string. The `psl::validate()` entry point should behave exactly the same as `psl::multi_schema()` with a single file named `schema.prisma`. In particular, it has the exact same return type.

Implementation
==============

This is achieved by extending `Span` to contain, in addition to a start and end offset, a `FileId`. The `FileId` is a unique identifier for a file and its parsed `SchemaAst` inside `ParserDatabase`. The identifier types for AST items in `ParserDatabase` are also extended to contain the `FileId`, so that they can be uniquely referred to in the context of the (multi-file) schema. After the analysis phase (the `parser_database` crate), consumers of the analyzed schema become multi-file aware completely transparently, no change is necessary in the other engines.

The only changes that will be required at scattered points across the codebase are the `psl::validate()` call sites that will need to receive a `Vec<Box<Path>, SourceFile>` instead of a single `SourceFile`. This PR does _not_ deal with that, but it makes where these call sites are obvious by what entry points they use: `psl::validate()`, `psl::parse_schema()` and the various `*_assert_single()` methods on `ParserDatabase`.

The PR contains tests confirming that schema analysis, validation and displaying diagnostics across multiple files works as expected.

Status of this PR
=================

This is going to be directly mergeable after review, and it will not affect the current schema handling behaviour when dealing with a single schema file.

Next steps
==========

- Replace all calls to `psl::validate()` with calls to `psl::validate_multi_file()`.
- The `*_assert_single()` calls should be progressively replaced with their multi-file counterparts across engines.
- The language server should start sending multiple files to prisma-schema-wasm in all calls. This is not in the spirit of the language server spec, but that is the most immediate solution. We'll have to make `range_to_span()` in `prisma-fmt` multi-schema aware by taking a FileId param.

Links
=====

Relevant issue: prisma/prisma#2377

Also see the [internal design doc](https://www.notion.so/prismaio/Multi-file-Schema-24d68fe8664048ad86252fe446caac24?d=68ef128f25974e619671a9855f65f44d#2889a038e68c4fe1ac9afe3cd34978bd).

* chore(prisma-fmt): fix typo

* chore(prisma-fmt): add comment

* chore(prisma-fmt): fix compilation after #4137

---------

Co-authored-by: Alberto Schiabel <jkomyno@users.noreply.github.com>
Co-authored-by: jkomyno <skiabo97@gmail.com>

prisma-fmt/src/code_actions.rs

@@ -31,8 +31,13 @@ pub(crate) fn available_actions(schema: String, params: CodeActionParams) -> Vec
 
     let datasource = config.datasources.first();
 
-    for source in validated_schema.db.ast().sources() {
-        relation_mode::edit_referential_integrity(&mut actions, &params, validated_schema.db.source(), source)
+    for source in validated_schema.db.ast_assert_single().sources() {
+        relation_mode::edit_referential_integrity(
+            &mut actions,
+            &params,
+            validated_schema.db.source_assert_single(),
+            source,
+        )
     }
 
     // models AND views
@@ -45,21 +50,27 @@ pub(crate) fn available_actions(schema: String, params: CodeActionParams) -> Vec
             multi_schema::add_schema_block_attribute_model(
                 &mut actions,
                 &params,
-                validated_schema.db.source(),
+                validated_schema.db.source_assert_single(),
                 config,
                 model,
             );
 
-            multi_schema::add_schema_to_schemas(&mut actions, &params, validated_schema.db.source(), config, model);
+            multi_schema::add_schema_to_schemas(
+                &mut actions,
+                &params,
+                validated_schema.db.source_assert_single(),
+                config,
+                model,
+            );
         }
 
         if matches!(datasource, Some(ds) if ds.active_provider == "mongodb") {
-            mongodb::add_at_map_for_id(&mut actions, &params, validated_schema.db.source(), model);
+            mongodb::add_at_map_for_id(&mut actions, &params, validated_schema.db.source_assert_single(), model);
 
             mongodb::add_native_for_auto_id(
                 &mut actions,
                 &params,
-                validated_schema.db.source(),
+                validated_schema.db.source_assert_single(),
                 model,
                 datasource.unwrap(),
             );
@@ -71,7 +82,7 @@ pub(crate) fn available_actions(schema: String, params: CodeActionParams) -> Vec
             multi_schema::add_schema_block_attribute_enum(
                 &mut actions,
                 &params,
-                validated_schema.db.source(),
+                validated_schema.db.source_assert_single(),
                 config,
                 enumerator,
             )
@@ -88,15 +99,15 @@ pub(crate) fn available_actions(schema: String, params: CodeActionParams) -> Vec
             relations::add_referenced_side_unique(
                 &mut actions,
                 &params,
-                validated_schema.db.source(),
+                validated_schema.db.source_assert_single(),
                 complete_relation,
             );
 
             if relation.is_one_to_one() {
                 relations::add_referencing_side_unique(
                     &mut actions,
                     &params,
-                    validated_schema.db.source(),
+                    validated_schema.db.source_assert_single(),
                     complete_relation,
                 );
             }
@@ -105,7 +116,7 @@ pub(crate) fn available_actions(schema: String, params: CodeActionParams) -> Vec
                 relations::add_index_for_relation_fields(
                     &mut actions,
                     &params,
-                    validated_schema.db.source(),
+                    validated_schema.db.source_assert_single(),
                     complete_relation.referencing_field(),
                 );
             }
@@ -114,7 +125,7 @@ pub(crate) fn available_actions(schema: String, params: CodeActionParams) -> Vec
                 relation_mode::replace_set_default_mysql(
                     &mut actions,
                     &params,
-                    validated_schema.db.source(),
+                    validated_schema.db.source_assert_single(),
                     complete_relation,
                     config,
                 )

prisma-fmt/src/code_actions/multi_schema.rs

@@ -142,7 +142,7 @@ pub(super) fn add_schema_to_schemas(
                 formatted_attribute,
                 true,
                 // todo: update spans so that we can just append to the end of the _inside_ of the array. Instead of needing to re-append the `]` or taking the span end -1
-                Span::new(span.start, span.end - 1),
+                Span::new(span.start, span.end - 1, psl::parser_database::FileId::ZERO),
                 params,
             )
         }

prisma-fmt/src/lib.rs

@@ -225,7 +225,7 @@ pub(crate) fn range_to_span(range: Range, document: &str) -> ast::Span {
     let start = position_to_offset(&range.start, document).unwrap();
     let end = position_to_offset(&range.end, document).unwrap();
 
-    ast::Span::new(start, end)
+    ast::Span::new(start, end, psl::parser_database::FileId::ZERO)
 }
 
 /// Gives the LSP position right after the given span.

prisma-fmt/src/text_document_completion.rs

@@ -41,7 +41,7 @@ pub(crate) fn completion(schema: String, params: CompletionParams) -> Completion
 
     let db = {
         let mut diag = Diagnostics::new();
-        ParserDatabase::new(source_file, &mut diag)
+        ParserDatabase::new_single_file(source_file, &mut diag)
     };
 
     let ctx = CompletionContext {
@@ -91,7 +91,7 @@ impl<'a> CompletionContext<'a> {
 }
 
 fn push_ast_completions(ctx: CompletionContext<'_>, completion_list: &mut CompletionList) {
-    match ctx.db.ast().find_at_position(ctx.position) {
+    match ctx.db.ast_assert_single().find_at_position(ctx.position) {
         ast::SchemaPosition::Model(
             _model_id,
             ast::ModelPosition::Field(_, ast::FieldPosition::Attribute("relation", _, Some(attr_name))),
@@ -190,7 +190,7 @@ fn ds_has_prop(ctx: CompletionContext<'_>, prop: &str) -> bool {
 
 fn push_namespaces(ctx: CompletionContext<'_>, completion_list: &mut CompletionList) {
     for (namespace, _) in ctx.namespaces() {
-        let insert_text = if add_quotes(ctx.params, ctx.db.source()) {
+        let insert_text = if add_quotes(ctx.params, ctx.db.source_assert_single()) {
             format!(r#""{namespace}""#)
         } else {
             namespace.to_string()

prisma-fmt/src/text_document_completion/datasource.rs

@@ -144,7 +144,7 @@ pub(super) fn url_env_db_completion(completion_list: &mut CompletionList, kind:
         _ => unreachable!(),
     };
 
-    let insert_text = if add_quotes(ctx.params, ctx.db.source()) {
+    let insert_text = if add_quotes(ctx.params, ctx.db.source_assert_single()) {
         format!(r#""{text}""#)
     } else {
         text.to_owned()

prisma-fmt/tests/code_actions/test_api.rs

@@ -19,8 +19,8 @@ fn parse_schema_diagnostics(file: impl Into<SourceFile>) -> Option<Vec<Diagnosti
                     severity: Some(DiagnosticSeverity::WARNING),
                     message: warn.message().to_owned(),
                     range: lsp_types::Range {
-                        start: offset_to_position(warn.span().start, schema.db.source()),
-                        end: offset_to_position(warn.span().end, schema.db.source()),
+                        start: offset_to_position(warn.span().start, schema.db.source_assert_single()),
+                        end: offset_to_position(warn.span().end, schema.db.source_assert_single()),
                     },
                     ..Default::default()
                 });
@@ -31,8 +31,8 @@ fn parse_schema_diagnostics(file: impl Into<SourceFile>) -> Option<Vec<Diagnosti
                     severity: Some(DiagnosticSeverity::ERROR),
                     message: error.message().to_owned(),
                     range: lsp_types::Range {
-                        start: offset_to_position(error.span().start, schema.db.source()),
-                        end: offset_to_position(error.span().end, schema.db.source()),
+                        start: offset_to_position(error.span().start, schema.db.source_assert_single()),
+                        end: offset_to_position(error.span().end, schema.db.source_assert_single()),
                     },
                     ..Default::default()
                 });

psl/diagnostics/src/lib.rs

@@ -8,5 +8,5 @@ mod warning;
 pub use collection::Diagnostics;
 pub use error::DatamodelError;
 pub use native_type_error_factory::NativeTypeErrorFactory;
-pub use span::Span;
+pub use span::{FileId, Span};
 pub use warning::DatamodelWarning;

psl/diagnostics/src/span.rs

@@ -1,19 +1,34 @@
+/// The stable identifier for a PSL file.
+#[derive(Debug, PartialEq, Clone, Copy, Hash, Eq, PartialOrd, Ord)]
+pub struct FileId(pub u32); // we can't encapsulate because it would be a circular crate
+                            // dependency between diagnostics and parser-database
+
+impl FileId {
+    pub const ZERO: FileId = FileId(0);
+    pub const MAX: FileId = FileId(u32::MAX);
+}
+
 /// Represents a location in a datamodel's text representation.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct Span {
     pub start: usize,
     pub end: usize,
+    pub file_id: FileId,
 }
 
 impl Span {
     /// Constructor.
-    pub fn new(start: usize, end: usize) -> Span {
-        Span { start, end }
+    pub fn new(start: usize, end: usize, file_id: FileId) -> Span {
+        Span { start, end, file_id }
     }
 
     /// Creates a new empty span.
     pub fn empty() -> Span {
-        Span { start: 0, end: 0 }
+        Span {
+            start: 0,
+            end: 0,
+            file_id: FileId::ZERO,
+        }
     }
 
     /// Is the given position inside the span? (boundaries included)
@@ -27,11 +42,12 @@ impl Span {
     }
 }
 
-impl From<pest::Span<'_>> for Span {
-    fn from(s: pest::Span<'_>) -> Self {
+impl From<(FileId, pest::Span<'_>)> for Span {
+    fn from((file_id, s): (FileId, pest::Span<'_>)) -> Self {
         Span {
             start: s.start(),
             end: s.end(),
+            file_id,
         }
     }
 }