Python bindings: make alg['datatype'] accept a GDT_ constant

autotest/utilities/test_gdalalg_raster_astype.py

@@ -15,23 +15,32 @@
 
 
 def get_astype_alg():
-    reg = gdal.GetGlobalAlgorithmRegistry()
-    raster = reg.InstantiateAlg("raster")
-    return raster.InstantiateSubAlgorithm("astype")
+    return gdal.GetGlobalAlgorithmRegistry()["raster"]["astype"]
 
 
 def test_gdalalg_raster_astype(tmp_vsimem):
 
     out_filename = str(tmp_vsimem / "out.tif")
 
     alg = get_astype_alg()
-    assert alg.ParseRunAndFinalize(
-        [
-            "--datatype=UInt16",
-            "../gcore/data/rgbsmall.tif",
-            out_filename,
-        ],
-    )
+    alg["datatype"] = "UInt16"
+    alg["input"] = "../gcore/data/rgbsmall.tif"
+    alg["output"] = out_filename
+    assert alg.Run() and alg.Finalize()
+
+    with gdal.OpenEx(out_filename) as ds:
+        assert ds.GetRasterBand(1).DataType == gdal.GDT_UInt16
+
+
+def test_gdalalg_raster_astype_as_gdt(tmp_vsimem):
+
+    out_filename = str(tmp_vsimem / "out.tif")
+
+    alg = get_astype_alg()
+    alg["datatype"] = gdal.GDT_UInt16
+    alg["input"] = "../gcore/data/rgbsmall.tif"
+    alg["output"] = out_filename
+    assert alg.Run() and alg.Finalize()
 
     with gdal.OpenEx(out_filename) as ds:
         assert ds.GetRasterBand(1).DataType == gdal.GDT_UInt16

gcore/gdalalgorithm.cpp

@@ -2914,13 +2914,15 @@ GDALInConstructionAlgorithmArg &
 GDALAlgorithm::AddOutputDataTypeArg(std::string *pValue,
                                     const char *helpMessage)
 {
-    auto &arg = AddArg(GDAL_ARG_NAME_OUTPUT_DATA_TYPE, 0,
-                       MsgOrDefault(helpMessage, _("Output data type")), pValue)
-                    .AddAlias("ot")
-                    .AddAlias("datatype")
-                    .SetChoices("Byte", "Int8", "UInt16", "Int16", "UInt32",
-                                "Int32", "UInt64", "Int64", "CInt16", "CInt32",
-                                "Float32", "Float64", "CFloat32", "CFloat64");
+    auto &arg =
+        AddArg(GDAL_ARG_NAME_OUTPUT_DATA_TYPE, 0,
+               MsgOrDefault(helpMessage, _("Output data type")), pValue)
+            .AddAlias("ot")
+            .AddAlias("datatype")
+            .AddMetadataItem("type", {"GDALDataType"})
+            .SetChoices("Byte", "Int8", "UInt16", "Int16", "UInt32", "Int32",
+                        "UInt64", "Int64", "CInt16", "CInt32", "Float16",
+                        "Float32", "Float64", "CFloat32", "CFloat64");
     return arg;
 }
 
@@ -4911,6 +4913,28 @@ char **GDALAlgorithmArgGetChoices(GDALAlgorithmArgH hArg)
     return CPLStringList(hArg->ptr->GetChoices()).StealList();
 }
 
+/************************************************************************/
+/*                  GDALAlgorithmArgGetMetadataItem()                   */
+/************************************************************************/
+
+/** Return the values of the metadata item of an argument.
+ *
+ * @param hArg Handle to an argument. Must NOT be null.
+ * @param pszItem Name of the item. Must NOT be null.
+ * @return a NULL terminated list of values, which must be destroyed with
+ * CSLDestroy()
+
+ * @since 3.11
+ */
+char **GDALAlgorithmArgGetMetadataItem(GDALAlgorithmArgH hArg,
+                                       const char *pszItem)
+{
+    VALIDATE_POINTER1(hArg, __func__, nullptr);
+    VALIDATE_POINTER1(pszItem, __func__, nullptr);
+    const auto pVecOfStrings = hArg->ptr->GetMetadataItem(pszItem);
+    return pVecOfStrings ? CPLStringList(*pVecOfStrings).StealList() : nullptr;
+}
+
 /************************************************************************/
 /*                   GDALAlgorithmArgIsExplicitlySet()                  */
 /************************************************************************/

gcore/gdalalgorithm.h

@@ -152,6 +152,8 @@ bool CPL_DLL GDALAlgorithmArgGetRepeatedArgAllowed(GDALAlgorithmArgH);
 
 char CPL_DLL **GDALAlgorithmArgGetChoices(GDALAlgorithmArgH);
 
+char CPL_DLL **GDALAlgorithmArgGetMetadataItem(GDALAlgorithmArgH, const char *);
+
 bool CPL_DLL GDALAlgorithmArgIsExplicitlySet(GDALAlgorithmArgH);
 
 bool CPL_DLL GDALAlgorithmArgHasDefaultValue(GDALAlgorithmArgH);

swig/include/Algorithm.i

@@ -118,6 +118,12 @@ public:
   }
 %clear char **;
 
+%apply (char **CSL) {char **};
+  char **GetMetadataItem(const char* item) {
+    return GDALAlgorithmArgGetMetadataItem( self, item );
+  }
+%clear char **;
+
   bool IsExplicitlySet() {
     return GDALAlgorithmArgIsExplicitlySet(self);
   }

swig/include/python/gdal_python.i

@@ -5557,7 +5557,12 @@ class VSIFile(BytesIO):
         if type == GAAT_BOOLEAN:
             return self.SetAsBoolean(value)
         if type == GAAT_STRING:
-            if isinstance(value, str) or isinstance(value, int) or isinstance(value, float):
+            if isinstance(value, int):
+                if "GDALDataType" in self.GetMetadataItem("type") and value >= GDT_Byte and value < GDT_TypeCount:
+                    return self.SetAsString(GetDataTypeName(value))
+                else:
+                    return self.SetAsString(str(value))
+            elif isinstance(value, str) or isinstance(value, float):
                 return self.SetAsString(str(value))
             else:
                 raise "Unexpected value type %s for an argument of type String" % str(type(value))