Move sdf anonymous layer default file format to usda. Introduces SDF_LEGACY_FILE_FORMAT_IMPORT, which currently allows the legacy "#sdf 1.4.32" cookie to be ingested as "#usda 1.0".

See PixarAnimationStudios#3012

(Internal change: 2366602)

Author: anwang2009

pxr/usd/sdf/CMakeLists.txt

@@ -204,6 +204,7 @@ pxr_test_scripts(
     testenv/testSdfFileFormat.py
     testenv/testSdfLayer.py
     testenv/testSdfLayerMuting.py
+    testenv/testSdfLegacyFileFormat.py
     testenv/testSdfListOp.py
     testenv/testSdfParsing.py
     testenv/testSdfPath.py
@@ -536,6 +537,20 @@ pxr_register_test(testSdfLayerMuting
     COMMAND "${CMAKE_INSTALL_PREFIX}/tests/testSdfLayerMuting"
 )
 
+pxr_register_test(testSdfLegacyFileFormat
+    PYTHON
+    ENV
+        SDF_FILE_FORMAT_LEGACY_IMPORT=allow
+    COMMAND "${CMAKE_INSTALL_PREFIX}/tests/testSdfLegacyFileFormat"
+)
+
+pxr_register_test(testSdfLegacyFileFormat_Error
+    PYTHON
+    ENV
+        SDF_FILE_FORMAT_LEGACY_IMPORT=error
+    COMMAND "${CMAKE_INSTALL_PREFIX}/tests/testSdfLegacyFileFormat"
+)
+
 pxr_register_test(testSdfListOp
     PYTHON
     COMMAND "${CMAKE_INSTALL_PREFIX}/tests/testSdfListOp"

pxr/usd/sdf/layer.cpp

@@ -27,9 +27,9 @@
 #include "pxr/usd/sdf/relationshipSpec.h"
 #include "pxr/usd/sdf/schema.h"
 #include "pxr/usd/sdf/specType.h"
-#include "pxr/usd/sdf/textFileFormat.h"
-#include "pxr/usd/sdf/types.h"
 #include "pxr/usd/sdf/subLayerListEditor.h"
+#include "pxr/usd/sdf/types.h"
+#include "pxr/usd/sdf/usdaFileFormat.h"
 #include "pxr/usd/sdf/variantSetSpec.h"
 #include "pxr/usd/sdf/variantSpec.h"
 
@@ -335,7 +335,7 @@ SdfLayer::CreateAnonymous(
     }
 
     if (!fileFormat) {
-        fileFormat = SdfFileFormat::FindById(SdfTextFileFormatTokens->Id);
+        fileFormat = SdfFileFormat::FindById(SdfUsdaFileFormatTokens->Id);
     }
 
     if (!fileFormat) {

pxr/usd/sdf/testenv/testSdfLegacyFileFormat.py

@@ -0,0 +1,29 @@
+#!/pxrpythonsubst
+#
+# Copyright 2025 Pixar
+#
+# Licensed under the terms set forth in the LICENSE.txt file available at
+# https://openusd.org/license.
+
+from pxr import Sdf, Tf
+import os
+import unittest
+
+class TestSdfLegacyFileFormat(unittest.TestCase):
+    def test_ReadLegacySdfFileFormat(self):
+        legacyRead = Tf.GetEnvSetting("SDF_FILE_FORMAT_LEGACY_IMPORT")
+
+        layer = Sdf.Layer.CreateAnonymous()
+        importStr = """#sdf 1.4.32
+            def "Prim" {}
+        """
+
+        if legacyRead == "allow" or legacyRead == "warn":
+            success = layer.ImportFromString(importStr)
+            self.assertTrue(success)
+        elif legacyRead == "error":
+            with self.assertRaises(Tf.ErrorException):
+                layer.ImportFromString(importStr)
+
+if __name__ == "__main__":
+    unittest.main()

pxr/usd/sdf/usdaFileFormat.cpp

@@ -36,6 +36,24 @@ TF_DEFINE_ENV_SETTING(
     "Warn when reading a text file (.usda or .usda derived) larger than this "
     "number of MB (no warnings if set to 0)");
 
+TF_DEFINE_ENV_SETTING(SDF_FILE_FORMAT_LEGACY_IMPORT, "allow",
+    "By default, we allow imported strings with the legacy `#sdf 1.4.32` "
+    "header format to be read as .usda version 1.0. When this is set to "
+    "'warn,' a warning will be emitted when the usda file format attempts "
+    "to import a string with header `#sdf 1.4.32`. When this is set to "
+    "'error', strings imported with the sdf header will no longer be ingested "
+    "and an error will be emitted.");
+
+TF_DEFINE_PRIVATE_TOKENS(
+    _tokens,
+
+    (allow)
+    (warn)
+    (error)
+    ((legacyCookie, "#sdf 1.4.32"))
+    ((modernCookie, "#usda 1.0"))
+);
+
 // Our interface to the parser for parsing to SdfData.
 extern bool Sdf_ParseLayer(
     const string& context, 
@@ -365,8 +383,34 @@ SdfUsdaFileFormat::ReadFromString(
     // code will eventually be removed, it's being put in place so as to provide 
     // backward compatibility for in-code layer constructs to work with pegtl 
     // parser also. This code should be removed when (USD-9838) gets worked on.
-    const std::string trimmedStr = TfStringTrimLeft(str);
+    std::string trimmedStr = TfStringTrimLeft(str);
 
+    // The legacy sdf format is deprecated in favor of the usda format.
+    // Since `sdf 1.4.32` is equivalent in content to `usda 1.0`, allow
+    // imported strings headed with the former to be read by the latter.
+    if (TfStringStartsWith(trimmedStr, _tokens->legacyCookie)) {
+        static const std::string readSdf =
+            TfGetEnvSetting(SDF_FILE_FORMAT_LEGACY_IMPORT);
+
+        if (_tokens->allow == readSdf || _tokens->warn == readSdf) {
+            trimmedStr = _tokens->modernCookie.GetString() + 
+                trimmedStr.substr((_tokens->legacyCookie).size());
+
+            if (_tokens->warn == readSdf) {
+                TF_WARN("'%s' is a deprecated format for reading. "
+                        "Use '%s' instead.",
+                        _tokens->legacyCookie.GetText(),
+                        _tokens->modernCookie.GetText());
+            }
+        } else {
+            TF_RUNTIME_ERROR("'%s' is not a supported format for reading. "
+                             "Use '%s' instead.",
+                             _tokens->legacyCookie.GetText(),
+                             _tokens->modernCookie.GetText());
+            return false;
+        }
+    }
+
     if (!Sdf_ParseLayerFromString(
             trimmedStr, GetFormatId(), GetVersionString(),
             TfDynamic_cast<SdfDataRefPtr>(data), &hints)) {