feat: Multi-file compilation

AGENTS.md

@@ -209,10 +209,9 @@ fn valid_query() {
       (function_declaration name: (identifier) @name)
     "#};
 
-    let query = Query::try_from(input).unwrap();
+    let res = Query::expect_valid_ast(input).unwrap();
 
-    assert!(query.is_valid());
-    insta::assert_snapshot!(query.dump_ast(), @"");
+    insta::assert_snapshot!(res, @"");
 }
 ```
 

crates/plotnik-cli/src/commands/debug/mod.rs

@@ -101,8 +101,10 @@ pub fn run(args: DebugArgs) {
     if let Some(ref q) = query
         && !q.is_valid()
     {
-        let src = query_source.as_ref().unwrap();
-        eprint!("{}", q.diagnostics().render_colored(src, args.color));
+        eprint!(
+            "{}",
+            q.diagnostics().render_colored(q.source_map(), args.color)
+        );
         std::process::exit(1);
     }
 }

crates/plotnik-cli/src/commands/exec.rs

@@ -2,7 +2,7 @@ use std::fs;
 use std::io::{self, Read};
 use std::path::PathBuf;
 
-use plotnik_lib::QueryBuilder;
+use plotnik_lib::{QueryBuilder, SourceMap};
 
 use super::debug::source::resolve_lang;
 
@@ -33,7 +33,7 @@ pub fn run(args: ExecArgs) {
     let lang = resolve_lang(&args.lang, &args.source_text, &args.source_file);
 
     // Parse query
-    let query_parsed = QueryBuilder::new(&query_source)
+    let query_parsed = QueryBuilder::new(SourceMap::one_liner(&query_source))
         .parse()
         .unwrap_or_else(|e| {
             eprintln!("error: {}", e);
@@ -46,7 +46,7 @@ pub fn run(args: ExecArgs) {
     // Link query against language
     let linked = query_analyzed.link(&lang);
     if !linked.is_valid() {
-        eprint!("{}", linked.diagnostics().render(&query_source));
+        eprint!("{}", linked.diagnostics().render(linked.source_map()));
         std::process::exit(1);
     }
 

crates/plotnik-cli/src/commands/types.rs

@@ -41,13 +41,13 @@ pub fn run(args: TypesArgs) {
         .link(&lang);
 
     if !query.is_valid() {
-        eprint!("{}", query.diagnostics().render(&query_source));
+        eprint!("{}", query.diagnostics().render(query.source_map()));
         std::process::exit(1);
     }
 
     // Link query against language
     if !query.is_valid() {
-        eprint!("{}", query.diagnostics().render(&query_source));
+        eprint!("{}", query.diagnostics().render(query.source_map()));
         std::process::exit(1);
     }
 

crates/plotnik-lib/src/diagnostics/message.rs

@@ -1,5 +1,7 @@
 use rowan::TextRange;
 
+use super::{SourceId, Span};
+
 /// Diagnostic kinds ordered by priority (highest priority first).
 ///
 /// When two diagnostics have overlapping spans, the higher-priority one
@@ -282,14 +284,14 @@ impl Fix {
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct RelatedInfo {
-    pub(crate) range: TextRange,
+    pub(crate) span: Span,
     pub(crate) message: String,
 }
 
 impl RelatedInfo {
-    pub fn new(range: TextRange, message: impl Into<String>) -> Self {
+    pub fn new(source: SourceId, range: TextRange, message: impl Into<String>) -> Self {
         Self {
-            range,
+            span: Span::new(source, range),
             message: message.into(),
         }
     }
@@ -298,6 +300,8 @@ impl RelatedInfo {
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub(crate) struct DiagnosticMessage {
     pub(crate) kind: DiagnosticKind,
+    /// Which source file this diagnostic belongs to.
+    pub(crate) source: SourceId,
     /// The range shown to the user (underlined in output).
     pub(crate) range: TextRange,
     /// The range used for suppression logic. Errors within another error's
@@ -312,9 +316,15 @@ pub(crate) struct DiagnosticMessage {
 }
 
 impl DiagnosticMessage {
-    pub(crate) fn new(kind: DiagnosticKind, range: TextRange, message: impl Into<String>) -> Self {
+    pub(crate) fn new(
+        source: SourceId,
+        kind: DiagnosticKind,
+        range: TextRange,
+        message: impl Into<String>,
+    ) -> Self {
         Self {
             kind,
+            source,
             range,
             suppression_range: range,
             message: message.into(),
@@ -324,8 +334,12 @@ impl DiagnosticMessage {
         }
     }
 
-    pub(crate) fn with_default_message(kind: DiagnosticKind, range: TextRange) -> Self {
-        Self::new(kind, range, kind.fallback_message())
+    pub(crate) fn with_default_message(
+        source: SourceId,
+        kind: DiagnosticKind,
+        range: TextRange,
+    ) -> Self {
+        Self::new(source, kind, range, kind.fallback_message())
     }
 
     pub(crate) fn severity(&self) -> Severity {
@@ -359,8 +373,8 @@ impl std::fmt::Display for DiagnosticMessage {
                 f,
                 " (related: {} at {}..{})",
                 related.message,
-                u32::from(related.range.start()),
-                u32::from(related.range.end())
+                u32::from(related.span.range.start()),
+                u32::from(related.span.range.end())
             )?;
         }
         for hint in &self.hints {

crates/plotnik-lib/src/diagnostics/mod.rs

@@ -11,6 +11,22 @@ pub use printer::DiagnosticsPrinter;
 
 use message::{DiagnosticMessage, Fix, RelatedInfo};
 
+// Re-export from query module
+pub use crate::query::{SourceId, SourceMap};
+
+/// A location that knows which source it belongs to.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Span {
+    pub source: SourceId,
+    pub range: TextRange,
+}
+
+impl Span {
+    pub fn new(source: SourceId, range: TextRange) -> Self {
+        Self { source, range }
+    }
+}
+
 #[derive(Debug, Clone, Default)]
 pub struct Diagnostics {
     messages: Vec<DiagnosticMessage>,
@@ -32,26 +48,15 @@ impl Diagnostics {
     /// Create a diagnostic with the given kind and span.
     ///
     /// Uses the kind's default message. Call `.message()` on the builder to override.
-    pub fn report(&mut self, kind: DiagnosticKind, range: TextRange) -> DiagnosticBuilder<'_> {
-        DiagnosticBuilder {
-            diagnostics: self,
-            message: DiagnosticMessage::with_default_message(kind, range),
-        }
-    }
-
-    /// Create an error diagnostic (legacy API, prefer `report()`).
-    pub fn error(&mut self, msg: impl Into<String>, range: TextRange) -> DiagnosticBuilder<'_> {
-        DiagnosticBuilder {
-            diagnostics: self,
-            message: DiagnosticMessage::new(DiagnosticKind::UnexpectedToken, range, msg),
-        }
-    }
-
-    /// Create a warning diagnostic (legacy API, prefer `report()`).
-    pub fn warning(&mut self, msg: impl Into<String>, range: TextRange) -> DiagnosticBuilder<'_> {
+    pub fn report(
+        &mut self,
+        source: SourceId,
+        kind: DiagnosticKind,
+        range: TextRange,
+    ) -> DiagnosticBuilder<'_> {
         DiagnosticBuilder {
             diagnostics: self,
-            message: DiagnosticMessage::new(DiagnosticKind::UnexpectedToken, range, msg),
+            message: DiagnosticMessage::with_default_message(source, kind, range),
         }
     }
 
@@ -163,29 +168,34 @@ impl Diagnostics {
         &self.messages
     }
 
-    pub fn printer<'a>(&self, source: &'a str) -> DiagnosticsPrinter<'a> {
-        DiagnosticsPrinter::new(self.messages.clone(), source)
+    /// Create a printer with a source map (multi-file support).
+    pub fn printer<'a>(&self, sources: &'a SourceMap) -> DiagnosticsPrinter<'a> {
+        DiagnosticsPrinter::new(self.messages.clone(), sources)
     }
 
-    /// Printer that uses filtered diagnostics (cascading errors suppressed).
-    pub fn filtered_printer<'a>(&self, source: &'a str) -> DiagnosticsPrinter<'a> {
-        DiagnosticsPrinter::new(self.filtered(), source)
+    /// Filtered printer with source map (cascading errors suppressed).
+    pub fn filtered_printer<'a>(&self, sources: &'a SourceMap) -> DiagnosticsPrinter<'a> {
+        DiagnosticsPrinter::new(self.filtered(), sources)
     }
 
-    pub fn render(&self, source: &str) -> String {
-        self.printer(source).render()
+    /// Render with source map.
+    pub fn render(&self, sources: &SourceMap) -> String {
+        self.printer(sources).render()
     }
 
-    pub fn render_colored(&self, source: &str, colored: bool) -> String {
-        self.printer(source).colored(colored).render()
+    /// Render with source map, colored output.
+    pub fn render_colored(&self, sources: &SourceMap, colored: bool) -> String {
+        self.printer(sources).colored(colored).render()
     }
 
-    pub fn render_filtered(&self, source: &str) -> String {
-        self.filtered_printer(source).render()
+    /// Render filtered with source map.
+    pub fn render_filtered(&self, sources: &SourceMap) -> String {
+        self.filtered_printer(sources).render()
     }
 
-    pub fn render_filtered_colored(&self, source: &str, colored: bool) -> String {
-        self.filtered_printer(source).colored(colored).render()
+    /// Render filtered with source map, colored output.
+    pub fn render_filtered_colored(&self, sources: &SourceMap, colored: bool) -> String {
+        self.filtered_printer(sources).colored(colored).render()
     }
 
     pub fn extend(&mut self, other: Diagnostics) {
@@ -201,8 +211,15 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
-    pub fn related_to(mut self, msg: impl Into<String>, range: TextRange) -> Self {
-        self.message.related.push(RelatedInfo::new(range, msg));
+    pub fn related_to(
+        mut self,
+        source: SourceId,
+        range: TextRange,
+        msg: impl Into<String>,
+    ) -> Self {
+        self.message
+            .related
+            .push(RelatedInfo::new(source, range, msg));
         self
     }
 

crates/plotnik-lib/src/diagnostics/printer.rs

@@ -5,30 +5,24 @@ use std::fmt::Write;
 use annotate_snippets::{AnnotationKind, Group, Level, Patch, Renderer, Snippet};
 use rowan::TextRange;
 
+use super::SourceMap;
 use super::message::{DiagnosticMessage, Severity};
 
 pub struct DiagnosticsPrinter<'a> {
     diagnostics: Vec<DiagnosticMessage>,
-    source: &'a str,
-    path: Option<&'a str>,
+    sources: &'a SourceMap,
     colored: bool,
 }
 
 impl<'a> DiagnosticsPrinter<'a> {
-    pub(crate) fn new(diagnostics: Vec<DiagnosticMessage>, source: &'a str) -> Self {
+    pub(crate) fn new(diagnostics: Vec<DiagnosticMessage>, sources: &'a SourceMap) -> Self {
         Self {
             diagnostics,
-            source,
-            path: None,
+            sources,
             colored: false,
         }
     }
 
-    pub fn path(mut self, path: &'a str) -> Self {
-        self.path = Some(path);
-        self
-    }
-
     pub fn colored(mut self, value: bool) -> Self {
         self.colored = value;
         self
@@ -48,33 +42,56 @@ impl<'a> DiagnosticsPrinter<'a> {
         };
 
         for (i, diag) in self.diagnostics.iter().enumerate() {
-            let range = adjust_range(diag.range, self.source.len());
+            let primary_content = self.sources.content(diag.source);
+            let range = adjust_range(diag.range, primary_content.len());
 
-            let mut snippet = Snippet::source(self.source)
-                .line_start(1)
-                .annotation(AnnotationKind::Primary.span(range.clone()));
-
-            if let Some(p) = self.path {
-                snippet = snippet.path(p);
+            let mut primary_snippet = Snippet::source(primary_content).line_start(1);
+            if let Some(name) = self.source_path(diag.source) {
+                primary_snippet = primary_snippet.path(name);
             }
+            primary_snippet =
+                primary_snippet.annotation(AnnotationKind::Primary.span(range.clone()));
+
+            // Collect same-file and cross-file related info separately
+            let mut cross_file_snippets = Vec::new();
 
             for related in &diag.related {
-                snippet = snippet.annotation(
-                    AnnotationKind::Context
-                        .span(adjust_range(related.range, self.source.len()))
-                        .label(&related.message),
-                );
+                if related.span.source == diag.source {
+                    // Same file: add annotation to primary snippet
+                    primary_snippet = primary_snippet.annotation(
+                        AnnotationKind::Context
+                            .span(adjust_range(related.span.range, primary_content.len()))
+                            .label(&related.message),
+                    );
+                } else {
+                    // Different file: create separate snippet
+                    let related_content = self.sources.content(related.span.source);
+                    let mut snippet = Snippet::source(related_content).line_start(1);
+                    if let Some(name) = self.source_path(related.span.source) {
+                        snippet = snippet.path(name);
+                    }
+                    snippet = snippet.annotation(
+                        AnnotationKind::Context
+                            .span(adjust_range(related.span.range, related_content.len()))
+                            .label(&related.message),
+                    );
+                    cross_file_snippets.push(snippet);
+                }
             }
 
             let level = severity_to_level(diag.severity());
-            let title_group = level.primary_title(&diag.message).element(snippet);
+            let mut title_group = level.primary_title(&diag.message).element(primary_snippet);
+
+            for snippet in cross_file_snippets {
+                title_group = title_group.element(snippet);
+            }
 
             let mut report: Vec<Group> = vec![title_group];
 
             if let Some(fix) = &diag.fix {
                 report.push(
                     Level::HELP.secondary_title(&fix.description).element(
-                        Snippet::source(self.source)
+                        Snippet::source(primary_content)
                             .line_start(1)
                             .patch(Patch::new(range, &fix.replacement)),
                     ),
@@ -93,6 +110,10 @@ impl<'a> DiagnosticsPrinter<'a> {
 
         Ok(())
     }
+
+    fn source_path(&self, source: crate::query::SourceId) -> Option<&'a str> {
+        self.sources.path(source)
+    }
 }
 
 fn severity_to_level(severity: Severity) -> Level<'static> {