fix: Local path normalization on Windows

Author: andyquinterom

R/00_classes.R

@@ -1,6 +1,17 @@
 #' @import S7
 NULL
 
+#' Check if a path is a local filesystem path (not a cloud URI)
+#'
+#' @param path Character. Path to check.
+#' @return Logical. TRUE if the path is a local filesystem path.
+#' @noRd
+is_local_path <- function(path) {
+  # Cloud storage URIs typically start with a scheme like s3://, gs://, az://, abfs://, etc.
+
+  !grepl("^[a-zA-Z][a-zA-Z0-9+.-]*://", path)
+}
+
 .onLoad <- function(...) {
   # Register cloud storage handlers (GCS, S3, Azure) for Delta Lake
 

R/delta_table.R

@@ -62,6 +62,11 @@ delta_table <- function(
     stop("'path' must be a single character string")
   }
 
+  # Normalize path if it's a local path to avoid mixed slashes on Windows
+  if (is_local_path(path)) {
+    path <- normalizePath(path, mustWork = FALSE, winslash = "/")
+  }
+
   if (!is.null(version) && !is.null(datetime)) {
     stop("Cannot specify both 'version' and 'datetime'")
   }
@@ -359,6 +364,11 @@ method(load_datetime, DeltaTable) <- function(table, ..., datetime) {
 #'
 #' @export
 is_delta_table_path <- function(path, storage_options = NULL) {
+  # Normalize path if it's a local path to avoid mixed slashes on Windows
+  if (is.character(path) && length(path) == 1 && is_local_path(path)) {
+    path <- normalizePath(path, mustWork = FALSE, winslash = "/")
+  }
+
   result <- is_delta_table(path, storage_options)
   if (methods::is(result, "error")) {
     rlang::abort(result$value)

R/merge.R

@@ -158,6 +158,11 @@ delta_merge <- function(
     stop("'table' must be a DeltaTable object or a single character path")
   }
 
+  # Normalize path if it's a local path to avoid mixed slashes on Windows
+  if (is_local_path(table_path)) {
+    table_path <- normalizePath(table_path, mustWork = FALSE, winslash = "/")
+  }
+
   DeltaMergeBuilder(
     table_path = table_path,
     storage_options = storage_options,

R/write.R

@@ -1,16 +1,6 @@
 #' @importFrom rlang abort
 NULL
 
-#' Check if a path is a local filesystem path (not a cloud URI)
-#'
-#' @param path Character. Path to check.
-#' @return Logical. TRUE if the path is a local filesystem path.
-#' @noRd
-is_local_path <- function(path) {
-  # Cloud storage URIs typically start with a scheme like s3://, gs://, az://, abfs://, etc.
-
-  !grepl("^[a-zA-Z][a-zA-Z0-9+.-]*://", path)
-}
 
 #' Ensure directory exists for local paths
 #'
@@ -120,6 +110,15 @@ write_deltalake <- function(
     stop("'table_or_uri' must be a single character string")
   }
 
+  # Normalize path if it's a local path to avoid mixed slashes on Windows
+  if (is_local_path(table_or_uri)) {
+    table_or_uri <- normalizePath(
+      table_or_uri,
+      mustWork = FALSE,
+      winslash = "/"
+    )
+  }
+
   # Create directory if it's a local path and doesn't exist
   ensure_directory_exists(table_or_uri)
 
@@ -227,6 +226,11 @@ create_deltalake <- function(
     stop("'table_uri' must be a single character string")
   }
 
+  # Normalize path if it's a local path to avoid mixed slashes on Windows
+  if (is_local_path(table_uri)) {
+    table_uri <- normalizePath(table_uri, mustWork = FALSE, winslash = "/")
+  }
+
   # Create directory if it's a local path and doesn't exist
   ensure_directory_exists(table_uri)
 

src/rust/src/lib.rs

@@ -127,18 +127,31 @@ pub(crate) fn parse_storage_options(opts: &List) -> HashMap<String, String> {
 
 /// Helper to convert a path string to URL
 pub(crate) fn path_to_url(path: &str) -> std::result::Result<url::Url, String> {
-    // Try parsing as URL first
-    if let Ok(url) = url::Url::parse(path) {
-        return Ok(url);
+    // Try parsing as URL first. On Windows, a path like "C:\..." might be
+    // parsed as a URL with scheme "C", so we only accept it as a URL if it
+    // contains "://" and the scheme is longer than 1 character (to avoid drive letters).
+    if path.contains("://") {
+        if let Ok(url) = url::Url::parse(path) {
+            if url.scheme().len() > 1 {
+                return Ok(url);
+            }
+        }
     }
 
     // Treat as local path
     let path_buf = std::path::Path::new(path);
-    let canonical = path_buf
-        .canonicalize()
-        .unwrap_or_else(|_| path_buf.to_path_buf());
 
-    url::Url::from_file_path(&canonical)
+    // Get absolute path. We avoid canonicalize() on Windows because it adds
+    // the \\?\ prefix which some object store implementations don't handle well.
+    let abs_path = if path_buf.is_absolute() {
+        path_buf.to_path_buf()
+    } else {
+        std::env::current_dir()
+            .map(|curr| curr.join(path_buf))
+            .unwrap_or_else(|_| path_buf.to_path_buf())
+    };
+
+    url::Url::from_file_path(&abs_path)
         .map_err(|_| format!("Failed to create URL from path: {}", path))
 }