Ruby: add minimal path transformer support

Supports only a minimal subset of the project layout specification;
enough to work with the transformers produced by the CLI when building
an overlay database.

Author: nickrolfe

ruby/extractor/src/extractor.rs

@@ -1,4 +1,5 @@
 use clap::Args;
+use codeql_extractor::file_paths::PathTransformer;
 use lazy_static::lazy_static;
 use rayon::prelude::*;
 use serde_json;
@@ -81,6 +82,7 @@ pub fn run(options: Options) -> std::io::Result<()> {
     let file_list = fs::File::open(file_paths::path_from_string(&options.file_list))?;
 
     let overlay_changed_files: Option<HashSet<PathBuf>> = get_overlay_changed_files();
+    let path_transformer = file_paths::load_path_transformer()?;
 
     let language: Language = tree_sitter_ruby::LANGUAGE.into();
     let erb: Language = tree_sitter_embedded_template::LANGUAGE.into();
@@ -105,7 +107,7 @@ pub fn run(options: Options) -> std::io::Result<()> {
                 }
                 _ => {},
             }
-            let src_archive_file = file_paths::path_for(&src_archive_dir, &path, "");
+            let src_archive_file = file_paths::path_for(&src_archive_dir, &path, "", path_transformer.as_ref());
             let mut source = std::fs::read(&path)?;
             let mut needs_conversion = false;
             let code_ranges;
@@ -118,6 +120,7 @@ pub fn run(options: Options) -> std::io::Result<()> {
                     &erb_schema,
                     &mut diagnostics_writer,
                     &mut trap_writer,
+                    path_transformer.as_ref(),
                     &path,
                     &source,
                     &[],
@@ -162,7 +165,7 @@ pub fn run(options: Options) -> std::io::Result<()> {
                                                     "character-decoding-error",
                                                     "Character decoding error",
                                                 )
-                                                .file(&file_paths::normalize_path(&path))
+                                                .file(&file_paths::normalize_and_transform_path(&path, path_transformer.as_ref()))
                                                 .message(
                                                     "Could not decode the file contents as {}: {}. The contents of the file must match the character encoding specified in the {} {}.",
                                                     &[
@@ -182,7 +185,7 @@ pub fn run(options: Options) -> std::io::Result<()> {
                             diagnostics_writer.write(
                                 diagnostics_writer
                                     .new_entry("unknown-character-encoding", "Could not process some files due to an unknown character encoding")
-                                    .file(&file_paths::normalize_path(&path))
+                                    .file(&file_paths::normalize_and_transform_path(&path, path_transformer.as_ref()))
                                     .message(
                                         "Unknown character encoding {} in {} {}.",
                                         &[
@@ -205,6 +208,7 @@ pub fn run(options: Options) -> std::io::Result<()> {
                 &schema,
                 &mut diagnostics_writer,
                 &mut trap_writer,
+                path_transformer.as_ref(),
                 &path,
                 &source,
                 &code_ranges,
@@ -215,14 +219,20 @@ pub fn run(options: Options) -> std::io::Result<()> {
             } else {
                 std::fs::copy(&path, &src_archive_file)?;
             }
-            write_trap(&trap_dir, path, &trap_writer, trap_compression)
+            write_trap(&trap_dir, path, &trap_writer, trap_compression, path_transformer.as_ref())
         })
         .expect("failed to extract files");
 
     let path = PathBuf::from("extras");
     let mut trap_writer = trap::Writer::new();
     extractor::populate_empty_location(&mut trap_writer);
-    let res = write_trap(&trap_dir, path, &trap_writer, trap_compression);
+    let res = write_trap(
+        &trap_dir,
+        path,
+        &trap_writer,
+        trap_compression,
+        path_transformer.as_ref(),
+    );
     if let Ok(output_path) = std::env::var("CODEQL_EXTRACTOR_RUBY_OVERLAY_BASE_METADATA_OUT") {
         // We're extracting an overlay base. For now, we don't have any metadata we need to store
         // that would get read when extracting the overlay, but the CLI expects us to write
@@ -254,8 +264,14 @@ fn write_trap(
     path: PathBuf,
     trap_writer: &trap::Writer,
     trap_compression: trap::Compression,
+    path_transformer: Option<&PathTransformer>,
 ) -> std::io::Result<()> {
-    let trap_file = file_paths::path_for(trap_dir, &path, trap_compression.extension());
+    let trap_file = file_paths::path_for(
+        trap_dir,
+        &path,
+        trap_compression.extension(),
+        path_transformer,
+    );
     std::fs::create_dir_all(trap_file.parent().unwrap())?;
     trap_writer.write_to_file(&trap_file, trap_compression)
 }

rust/extractor/src/archive.rs

@@ -15,7 +15,7 @@ impl Archiver {
     }
 
     fn try_archive(&self, source: &Path) -> std::io::Result<()> {
-        let dest = file_paths::path_for(&self.root, source, "");
+        let dest = file_paths::path_for(&self.root, source, "", None);
         if fs::metadata(&dest).is_ok() {
             return Ok(());
         }

rust/extractor/src/trap.rs

@@ -212,7 +212,7 @@ impl TrapFile {
         );
     }
     pub fn emit_file(&mut self, absolute_path: &Path) -> Label<generated::File> {
-        let untyped = extractor::populate_file(&mut self.writer, absolute_path);
+        let untyped = extractor::populate_file(&mut self.writer, absolute_path, None);
         // SAFETY: populate_file emits `@file` typed labels
         unsafe { Label::from_untyped(untyped) }
     }
@@ -268,6 +268,7 @@ impl TrapFileProvider {
             &self.trap_dir.join(category),
             key.as_ref(),
             self.compression.extension(),
+            None,
         );
         debug!("creating trap file {}", path.display());
         let mut writer = trap::Writer::new();

shared/tree-sitter-extractor/src/extractor/mod.rs

@@ -67,19 +67,26 @@ pub fn default_subscriber_with_level(
             ),
         )
 }
-pub fn populate_file(writer: &mut trap::Writer, absolute_path: &Path) -> trap::Label {
+pub fn populate_file(
+    writer: &mut trap::Writer,
+    absolute_path: &Path,
+    transformer: Option<&file_paths::PathTransformer>,
+) -> trap::Label {
     let (file_label, fresh) = writer.global_id(&trap::full_id_for_file(
-        &file_paths::normalize_path(absolute_path),
+        &file_paths::normalize_and_transform_path(absolute_path, transformer),
     ));
     if fresh {
         writer.add_tuple(
             "files",
             vec![
                 trap::Arg::Label(file_label),
-                trap::Arg::String(file_paths::normalize_path(absolute_path)),
+                trap::Arg::String(file_paths::normalize_and_transform_path(
+                    absolute_path,
+                    transformer,
+                )),
             ],
         );
-        populate_parent_folders(writer, file_label, absolute_path.parent());
+        populate_parent_folders(writer, file_label, absolute_path.parent(), transformer);
     }
     file_label
 }
@@ -117,16 +124,17 @@ pub fn populate_parent_folders(
     writer: &mut trap::Writer,
     child_label: trap::Label,
     path: Option<&Path>,
+    transformer: Option<&file_paths::PathTransformer>,
 ) {
     let mut path = path;
     let mut child_label = child_label;
     loop {
         match path {
             None => break,
             Some(folder) => {
-                let (folder_label, fresh) = writer.global_id(&trap::full_id_for_folder(
-                    &file_paths::normalize_path(folder),
-                ));
+                let parent = folder.parent();
+                let folder = file_paths::normalize_and_transform_path(folder, transformer);
+                let (folder_label, fresh) = writer.global_id(&trap::full_id_for_folder(&folder));
                 writer.add_tuple(
                     "containerparent",
                     vec![
@@ -137,12 +145,9 @@ pub fn populate_parent_folders(
                 if fresh {
                     writer.add_tuple(
                         "folders",
-                        vec![
-                            trap::Arg::Label(folder_label),
-                            trap::Arg::String(file_paths::normalize_path(folder)),
-                        ],
+                        vec![trap::Arg::Label(folder_label), trap::Arg::String(folder)],
                     );
-                    path = folder.parent();
+                    path = parent;
                     child_label = folder_label;
                 } else {
                     break;
@@ -205,11 +210,12 @@ pub fn extract(
     schema: &NodeTypeMap,
     diagnostics_writer: &mut diagnostics::LogWriter,
     trap_writer: &mut trap::Writer,
+    transformer: Option<&file_paths::PathTransformer>,
     path: &Path,
     source: &[u8],
     ranges: &[Range],
 ) {
-    let path_str = file_paths::normalize_path(path);
+    let path_str = file_paths::normalize_and_transform_path(path, transformer);
     let span = tracing::span!(
         tracing::Level::TRACE,
         "extract",
@@ -225,7 +231,7 @@ pub fn extract(
     parser.set_included_ranges(ranges).unwrap();
     let tree = parser.parse(source, None).expect("Failed to parse file");
     trap_writer.comment(format!("Auto-generated TRAP file for {}", path_str));
-    let file_label = populate_file(trap_writer, path);
+    let file_label = populate_file(trap_writer, path, transformer);
     let mut visitor = Visitor::new(
         source,
         diagnostics_writer,

shared/tree-sitter-extractor/src/extractor/simple.rs

@@ -123,7 +123,7 @@ impl Extractor {
                 let mut diagnostics_writer = diagnostics.logger();
                 let path = PathBuf::from(line).canonicalize()?;
                 let src_archive_file =
-                    crate::file_paths::path_for(&self.source_archive_dir, &path, "");
+                    crate::file_paths::path_for(&self.source_archive_dir, &path, "", None);
                 let source = std::fs::read(&path)?;
                 let mut trap_writer = trap::Writer::new();
 
@@ -152,6 +152,7 @@ impl Extractor {
                                     &schemas[i],
                                     &mut diagnostics_writer,
                                     &mut trap_writer,
+                                    None,
                                     &path,
                                     &source,
                                     &[],
@@ -183,7 +184,7 @@ fn write_trap(
     trap_writer: &trap::Writer,
     trap_compression: trap::Compression,
 ) -> std::io::Result<()> {
-    let trap_file = crate::file_paths::path_for(trap_dir, path, trap_compression.extension());
+    let trap_file = crate::file_paths::path_for(trap_dir, path, trap_compression.extension(), None);
     std::fs::create_dir_all(trap_file.parent().unwrap())?;
     trap_writer.write_to_file(&trap_file, trap_compression)
 }

shared/tree-sitter-extractor/src/file_paths.rs

@@ -1,8 +1,81 @@
-use std::path::{Path, PathBuf};
+use std::{
+    fs,
+    path::{Path, PathBuf},
+};
 
-/// Normalizes the path according the common CodeQL specification. Assumes that
-/// `path` has already been canonicalized using `std::fs::canonicalize`.
-pub fn normalize_path(path: &Path) -> String {
+/// This represents the minimum supported path transofmration that is needed to support extracting
+/// overlay databases. Specifically, it represents a transformer where one path prefix is replaced
+/// with a different prefix.
+pub struct PathTransformer {
+    pub original: String,
+    pub replacement: String,
+}
+
+/// Normalizes the path according to the common CodeQL specification, and, applies the given path
+/// transformer, if any. Assumes that `path` has already been canonicalized using
+/// `std::fs::canonicalize`.
+pub fn normalize_and_transform_path(path: &Path, transformer: Option<&PathTransformer>) -> String {
+    let path = normalize_path(path);
+    match transformer {
+        Some(transformer) => match path.strip_prefix(&transformer.original) {
+            Some(suffix) => format!("{}{}", transformer.replacement, suffix),
+            None => path,
+        },
+        None => path,
+    }
+}
+
+/**
+ * Attempts to load a path transformer.
+ *
+ * If the `CODEQL_PATH_TRANSFORMER` environment variable is not set, no transformer has been
+ * specified and the function returns `Ok(None)`.
+ *
+ * If the environment variable is set, the function attempts to load the transformer from the file
+ * at the * specified path. If this is successful, it returns `Ok(Some(PathTransformer))`.
+ *
+ * If the file cannot be read, or if it does not match the minimal subset of the path-transformer
+ * syntax supported by this extractor, the function returns an error.
+ */
+pub fn load_path_transformer() -> std::io::Result<Option<PathTransformer>> {
+    let path = match std::env::var("CODEQL_PATH_TRANSFORMER") {
+        Ok(p) => p,
+        Err(_) => return Ok(None),
+    };
+    let file_content = fs::read_to_string(path)?;
+    let lines = file_content
+        .lines()
+        .map(|line| line.trim().to_owned())
+        .filter(|line| !line.is_empty())
+        .collect::<Vec<String>>();
+
+    if lines.len() != 2 {
+        return Err(unsupported_transformer_error());
+    }
+    let replacement = lines[0]
+        .strip_prefix('#')
+        .ok_or(unsupported_transformer_error())?;
+    let original = lines[1]
+        .strip_suffix("//")
+        .ok_or(unsupported_transformer_error())?;
+
+    Ok(Some(PathTransformer {
+        original: original.to_owned(),
+        replacement: replacement.to_owned(),
+    }))
+}
+
+fn unsupported_transformer_error() -> std::io::Error {
+    std::io::Error::new(
+        std::io::ErrorKind::InvalidData,
+        "This extractor only supports path transformers specifying a single path-prefix rewrite, \
+         with the first line starting with a # and the second line ending with //.",
+    )
+}
+
+/// Normalizes the path according to the common CodeQL specification. Assumes that `path` has
+/// already been canonicalized using `std::fs::canonicalize`.
+fn normalize_path(path: &Path) -> String {
     if cfg!(windows) {
         // The way Rust canonicalizes paths doesn't match the CodeQL spec, so we
         // have to do a bit of work removing certain prefixes and replacing
@@ -93,7 +166,18 @@ pub fn path_from_string(path: &str) -> PathBuf {
     result
 }
 
-pub fn path_for(dir: &Path, path: &Path, ext: &str) -> PathBuf {
+pub fn path_for(
+    dir: &Path,
+    path: &Path,
+    ext: &str,
+    transformer: Option<&PathTransformer>,
+) -> PathBuf {
+    let path = if transformer.is_some() {
+        let transformed = normalize_and_transform_path(path, transformer);
+        PathBuf::from(transformed)
+    } else {
+        path.to_path_buf()
+    };
     let mut result = PathBuf::from(dir);
     for component in path.components() {
         match component {