From e2989901c21010d86f531354b1b39f932dbf2772 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Wed, 5 Feb 2025 22:22:09 +0100
Subject: [PATCH] gdal vector pipeline steps in standalone mode: allow
 --of=stream

---
 apps/gdalalg_vector_pipeline.cpp | 18 +++++++++++++-----
 gcore/gdalalgorithm.cpp          | 27 ++++++++++++++++++---------
 gcore/gdalalgorithm.h            |  5 +++--
 3 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/apps/gdalalg_vector_pipeline.cpp b/apps/gdalalg_vector_pipeline.cpp
index eba4c0ae10ab..dc26d831f9d9 100644
--- a/apps/gdalalg_vector_pipeline.cpp
+++ b/apps/gdalalg_vector_pipeline.cpp
@@ -72,7 +72,7 @@ void GDALVectorPipelineStepAlgorithm::AddInputArgs(bool hiddenForCLI)
 void GDALVectorPipelineStepAlgorithm::AddOutputArgs(
     bool hiddenForCLI, bool shortNameOutputLayerAllowed)
 {
-    AddOutputFormatArg(&m_format)
+    AddOutputFormatArg(&m_format, true)
         .AddMetadataItem(GAAMDI_REQUIRED_CAPABILITIES,
                          {GDAL_DCAP_VECTOR, GDAL_DCAP_CREATE})
         .SetHiddenForCLI(hiddenForCLI);
@@ -138,13 +138,21 @@ bool GDALVectorPipelineStepAlgorithm::RunImpl(GDALProgressFunc pfnProgress,
             m_outputDataset.Set(nullptr);
             if (RunStep(nullptr, nullptr))
             {
-                writeAlg.m_inputDataset.Set(m_outputDataset.GetDatasetRef());
-                if (writeAlg.Run(pfnProgress, pProgressData))
+                if (m_format == "stream")
                 {
-                    m_outputDataset.Set(
-                        writeAlg.m_outputDataset.GetDatasetRef());
                     ret = true;
                 }
+                else
+                {
+                    writeAlg.m_inputDataset.Set(
+                        m_outputDataset.GetDatasetRef());
+                    if (writeAlg.Run(pfnProgress, pProgressData))
+                    {
+                        m_outputDataset.Set(
+                            writeAlg.m_outputDataset.GetDatasetRef());
+                        ret = true;
+                    }
+                }
             }
         }
 
diff --git a/gcore/gdalalgorithm.cpp b/gcore/gdalalgorithm.cpp
index 0ddf208f13f8..5d47ad0f14fc 100644
--- a/gcore/gdalalgorithm.cpp
+++ b/gcore/gdalalgorithm.cpp
@@ -2328,12 +2328,17 @@ GDALAlgorithm::AddOpenOptionsArg(std::vector<std::string> *pValue)
 /*                            ValidateFormat()                          */
 /************************************************************************/
 
-bool GDALAlgorithm::ValidateFormat(const GDALAlgorithmArg &arg) const
+bool GDALAlgorithm::ValidateFormat(const GDALAlgorithmArg &arg,
+                                   bool bStreamAllowed) const
 {
     if (arg.GetChoices().empty())
     {
-        const auto Validate = [this, &arg](const std::string &val)
+        const auto Validate =
+            [this, &arg, bStreamAllowed](const std::string &val)
         {
+            if (bStreamAllowed && val == "stream")
+                return true;
+
             auto hDriver = GDALGetDriverByName(val.c_str());
             if (!hDriver)
             {
@@ -2451,7 +2456,8 @@ GDALAlgorithm::AddInputFormatsArg(std::vector<std::string> *pValue)
         AddArg(GDAL_ARG_NAME_INPUT_FORMAT, 0, _("Input formats"), pValue)
             .AddAlias("if")
             .SetCategory(GAAC_ADVANCED);
-    arg.AddValidationAction([this, &arg]() { return ValidateFormat(arg); });
+    arg.AddValidationAction([this, &arg]()
+                            { return ValidateFormat(arg, false); });
     arg.SetAutoCompleteFunction([&arg](const std::string &)
                                 { return FormatAutoCompleteFunction(arg); });
     return arg;
@@ -2462,13 +2468,16 @@ GDALAlgorithm::AddInputFormatsArg(std::vector<std::string> *pValue)
 /************************************************************************/
 
 GDALInConstructionAlgorithmArg &
-GDALAlgorithm::AddOutputFormatArg(std::string *pValue)
+GDALAlgorithm::AddOutputFormatArg(std::string *pValue, bool bStreamAllowed)
 {
-    auto &arg =
-        AddArg(GDAL_ARG_NAME_OUTPUT_FORMAT, 'f', _("Output format"), pValue)
-            .AddAlias("of")
-            .AddAlias("format");
-    arg.AddValidationAction([this, &arg]() { return ValidateFormat(arg); });
+    auto &arg = AddArg(GDAL_ARG_NAME_OUTPUT_FORMAT, 'f',
+                       bStreamAllowed ? _("Output format (\"stream\" allowed)")
+                                      : _("Output format"),
+                       pValue)
+                    .AddAlias("of")
+                    .AddAlias("format");
+    arg.AddValidationAction([this, &arg, bStreamAllowed]()
+                            { return ValidateFormat(arg, bStreamAllowed); });
     arg.SetAutoCompleteFunction([&arg](const std::string &)
                                 { return FormatAutoCompleteFunction(arg); });
     return arg;
diff --git a/gcore/gdalalgorithm.h b/gcore/gdalalgorithm.h
index be7019bbf297..0399e8e9f409 100644
--- a/gcore/gdalalgorithm.h
+++ b/gcore/gdalalgorithm.h
@@ -2153,7 +2153,8 @@ class CPL_DLL GDALAlgorithmRegistry
     GDALInConstructionAlgorithmArg &AddOutputStringArg(std::string *pValue);
 
     /** Add output format argument. */
-    GDALInConstructionAlgorithmArg &AddOutputFormatArg(std::string *pValue);
+    GDALInConstructionAlgorithmArg &
+    AddOutputFormatArg(std::string *pValue, bool bStreamAllowed = false);
 
     /** Add creation option(s) argument. */
     GDALInConstructionAlgorithmArg &
@@ -2241,7 +2242,7 @@ class CPL_DLL GDALAlgorithmRegistry
                          std::vector<double>, std::vector<GDALArgDatasetValue>>>
             &inConstructionValues);
 
-    bool ValidateFormat(const GDALAlgorithmArg &arg) const;
+    bool ValidateFormat(const GDALAlgorithmArg &arg, bool bStreamAllowed) const;
 
     virtual bool RunImpl(GDALProgressFunc pfnProgress, void *pProgressData) = 0;