(arrow) branch main updated: MINOR: [Docs][C++] Clarify ARROW_TEST_DATA requirement for tests (#48789)

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The following commit(s) were added to refs/heads/main by this push:
     new 287c749468 MINOR: [Docs][C++] Clarify ARROW_TEST_DATA requirement for tests (#48789)
287c749468 is described below

commit 287c749468bb0254ca910a9053efd04834ec32d6
Author: meher745 <75...@users.noreply.github.com>
AuthorDate: Fri Sep 4 17:30:30 2026 +0530

    MINOR: [Docs][C++] Clarify ARROW_TEST_DATA requirement for tests (#48789)
    
    
    ### Rationale for this change
    
    While setting up the C++ build on macOS, I encountered an IOError during testing because ARROW_TEST_DATA and PARQUET_TEST_DATA were not set. The current documentation lacks a clear warning that these exports are mandatory for a successful test pass.
    
    ### What changes are included in this PR?
    
    I added a .. note:: block to building.rst clarifying the need to initialize submodules and export absolute paths for test data folders.
    
    ### Are these changes tested?
    
    Yes, I built the documentation locally using Sphinx (make html) to verify the formatting renders correctly.
    
    ### Are there any user-facing changes?
    
    Yes, this updates the developer-facing documentation for C++ building.
    
    Authored-by: Meher <me...@gmail.com>
    Signed-off-by: Nic Crane <th...@gmail.com>
---
 docs/source/developers/cpp/building.rst | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/docs/source/developers/cpp/building.rst b/docs/source/developers/cpp/building.rst
index 33530779f5..fb68152287 100644
--- a/docs/source/developers/cpp/building.rst
+++ b/docs/source/developers/cpp/building.rst
@@ -314,6 +314,25 @@ The unit tests are not built by default. After building, one can also invoke
 the unit tests using the ``ctest`` tool provided by CMake (note that ``test``
 depends on ``python`` being available).
 
+.. note::
+   If you are building with tests (``-DARROW_BUILD_TESTS=ON``), you must ensure
+   the test data submodules are initialized and the environment variables
+   ``ARROW_TEST_DATA`` and ``PARQUET_TEST_DATA`` are set. Without these, several
+   tests (especially IPC and Parquet tests) will fail with an ``IOError``.
+
+   To initialize submodules, run:
+
+   .. code-block:: shell
+
+      $ git submodule update --init --recursive
+
+   Then set the variables to the absolute paths of your testing data folders:
+
+   .. code-block:: shell
+
+      $ export ARROW_TEST_DATA="<absolute_path_to_arrow>/testing/data"
+      $ export PARQUET_TEST_DATA="<absolute_path_to_arrow>/cpp/submodules/parquet-testing/data"
+
 On some Linux distributions, running the test suite might require setting an
 explicit locale. If you see any locale-related errors, try setting the
 environment variable (which requires the ``locales`` package or equivalent):