runfiles

Author: abrisco

ada/private/common.bzl

@@ -191,6 +191,9 @@ def _bind(
     args.add("--rename")
     args.add(binder_cwd_name + ".ads")
     args.add(binder_ads)
+    args.add("--rename")
+    args.add(binder_cwd_name + ".o")
+    args.add(binder_obj)
     args.add("--")
 
     # Command 1: gnatbind
@@ -202,14 +205,16 @@ def _bind(
     args.add(binder_cwd_name + ".adb")
     args.add(main_ali)
 
-    # Command 2: compile the binder output
+    # Command 2: compile the binder output.
+    # GNAT requires the object filename to match the compilation unit name,
+    # so we output to the CWD-relative name and let process_wrapper rename.
     args.add("++")
     args.add(compiler)
     args.add("-c")
     args.add("-I.")
     args.add(binder_cwd_name + ".adb")
     args.add("-o")
-    args.add(binder_obj)
+    args.add(binder_cwd_name + ".o")
 
     actions.run(
         executable = process_wrapper,

ada/runfiles/BUILD.bazel

@@ -0,0 +1,10 @@
+load("//ada:defs.bzl", "ada_library")
+
+ada_library(
+    name = "runfiles",
+    srcs = [
+        "runfiles.adb",
+        "runfiles.ads",
+    ],
+    visibility = ["//visibility:public"],
+)

ada/runfiles/README.md

@@ -0,0 +1,115 @@
+# Ada Runfiles Library
+
+Resolve [Bazel runfile](https://bazel.build/extending/rules#runfiles) paths at
+runtime from Ada binaries and tests.
+
+## Setup
+
+Add `@rules_ada//ada/runfiles` as a dependency and list any runtime data files
+in the `data` attribute:
+
+```python
+load("@rules_ada//ada:defs.bzl", "ada_binary")
+
+ada_binary(
+    name = "my_binary",
+    srcs = ["main.adb"],
+    data = ["//path/to:data.txt"],
+    deps = ["@rules_ada//ada/runfiles"],
+)
+```
+
+## Usage
+
+```ada
+with Ada.Text_IO;
+with Runfiles;
+
+procedure Main is
+   R    : constant Runfiles.Context := Runfiles.Create;
+   Path : constant String :=
+     R.Rlocation ("my_workspace/path/to/data.txt");
+begin
+   Ada.Text_IO.Put_Line ("File is at: " & Path);
+end Main;
+```
+
+### Bzlmod repo mapping
+
+When using [Bzlmod](https://bazel.build/external/overview#bzlmod), repository
+names seen at build time (apparent names) may differ from the canonical names
+used in the runfiles tree. Use the `Rlocation` overload with `Source_Repo` to
+apply the `_repo_mapping` translations automatically:
+
+```ada
+Path : constant String :=
+  R.Rlocation ("my_dep/data/config.json",
+                Source_Repo => "");
+```
+
+`Source_Repo` identifies the repository that is performing the lookup. For the
+root module this is `""` (empty string). The library reads the `_repo_mapping`
+file produced by Bazel and translates the apparent repo name (first path
+component) to its canonical name before resolving.
+
+## API reference
+
+### `Runfiles.Create`
+
+```ada
+function Create return Context;
+```
+
+Creates a runfiles context by examining, in order:
+
+1. `RUNFILES_MANIFEST_FILE` environment variable (manifest mode)
+2. `RUNFILES_DIR` environment variable (directory mode)
+3. `TEST_SRCDIR` environment variable (directory mode, set by Bazel test runner)
+4. `argv[0].runfiles` sibling directory
+5. Ancestor directories ending in `.runfiles`
+
+If a `MANIFEST` file exists inside the discovered directory, manifest mode is
+used instead of directory mode.
+
+Raises `Runfiles_Error` if no runfiles can be located.
+
+### `Runfiles.Rlocation`
+
+```ada
+function Rlocation (Self : Context; Path : String) return String;
+```
+
+Resolves an rlocation path (e.g. `"my_repo/path/to/file"`) to a real filesystem
+path. Absolute paths are returned unchanged.
+
+- **Manifest mode**: looks up the path in the parsed manifest. Raises
+  `Runfiles_Error` if not found.
+- **Directory mode**: joins the runfiles directory with the path. Does not check
+  whether the file exists on disk.
+
+### `Runfiles.Rlocation` (bzlmod-aware)
+
+```ada
+function Rlocation
+  (Self        : Context;
+   Path        : String;
+   Source_Repo : String) return String;
+```
+
+Same as above, but first applies the `_repo_mapping` to translate the apparent
+repository name (first path component) using the given `Source_Repo` as the
+lookup key. Falls back to the unmapped path if no mapping entry exists.
+
+Supports both the standard and compact repo mapping formats, including the
+wildcard prefix entries from
+[`--incompatible_compact_repo_mapping_manifest`](https://github.com/bazelbuild/bazel/issues/26262)
+(Bazel 9+).
+
+### `Runfiles_Error`
+
+```ada
+Runfiles_Error : exception;
+```
+
+Raised when runfiles cannot be located (`Create`) or a specific path cannot be
+resolved in manifest mode (`Rlocation`).