Fix Shape operator specification: correct range bounds and document start > end behavior (onnx#7132)

The Shape operator specification incorrectly stated that axes are
clamped to the range `[0, r-1]`, but since the `end` parameter is
exclusive in slicing operations, the correct range should be `[0, r]`.
Additionally, the spec was missing documentation for the `start > end`
case.

## Changes Made

### Documentation Fixes
- **Corrected range specification**: Changed from `[0, r-1]` to `[0, r]`
in all Shape operator documentation
- **Added start > end behavior**: Added "If start > end, the result will
be an empty shape." to clarify edge case behavior

### Affected Versions
Updated documentation for all Shape operator versions that support
`start` and `end` attributes:
- `Shape_ver24_doc` (current version)
- `Shape_ver23_doc` 
- `Shape_ver19_doc`
- `Shape_ver15_doc`

Note: Older versions (ver13, ver1) don't have `start`/`end` attributes
so no changes were needed.

### Test Coverage
- Added test case `test_shape("_start_greater_than_end", x, start=2,
end=1)` to validate the documented behavior
- Verified that the reference implementation correctly returns an empty
array when `start > end`

## Implementation Verification

The underlying C++ implementation was already correct - it properly
clamps both `start` and `end` to `[0, rank]` and handles the `start >
end` case by returning an empty shape:

```cpp
start = (start < 0) ? 0 : (start > rank) ? rank : start;
end = (end < 0) ? 0 : (end > rank) ? rank : end;
output_length->set_dim_value((end - start) < 0 ? 0 : (end - start));
```

This fix ensures the documentation accurately reflects the actual
behavior, making it consistent with how ONNX Runtime handles these edge
cases.

Fixes onnx#6862.

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---------

Signed-off-by: Justin Chu <justinchuby@users.noreply.github.com>
Signed-off-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: justinchuby <11205048+justinchuby@users.noreply.github.com>
Co-authored-by: Justin Chu <justinchuby@users.noreply.github.com>

Author: Copilot

docs/Changelog.md

@@ -19866,11 +19866,11 @@ This version of the operator has been available since version 15 of the default
   The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
   If the end axis is omitted, the axes upto the last one will be included.
   Negative axes indicate counting back from the last axis.
-  Note that axes will be clamped to the range [0, r-1], where r is the
+  Note that axes will be clamped to the range [0, r], where r is the
   rank of the input tensor if they are out-of-range (after adding r in the case of
   negative axis). Thus, specifying any end value > r is equivalent to specifying an end
   value of r, and specifying any start value < -r is equivalent to specifying a start
-  value of 0.
+  value of 0. If start > end, the result will be an empty shape.
 
   Examples:
 
@@ -23815,11 +23815,11 @@ This version of the operator has been available since version 19 of the default
   The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
   If the end axis is omitted, the axes upto the last one will be included.
   Negative axes indicate counting back from the last axis.
-  Note that axes will be clamped to the range [0, r-1], where r is the
+  Note that axes will be clamped to the range [0, r], where r is the
   rank of the input tensor if they are out-of-range (after adding r in the case of
   negative axis). Thus, specifying any end value > r is equivalent to specifying an end
   value of r, and specifying any start value < -r is equivalent to specifying a start
-  value of 0.
+  value of 0. If start > end, the result will be an empty shape.
 
   Examples:
 
@@ -25660,11 +25660,11 @@ This version of the operator has been available since version 21 of the default
   The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
   If the end axis is omitted, the axes upto the last one will be included.
   Negative axes indicate counting back from the last axis.
-  Note that axes will be clamped to the range [0, r-1], where r is the
+  Note that axes will be clamped to the range [0, r], where r is the
   rank of the input tensor if they are out-of-range (after adding r in the case of
   negative axis). Thus, specifying any end value > r is equivalent to specifying an end
   value of r, and specifying any start value < -r is equivalent to specifying a start
-  value of 0.
+  value of 0. If start > end, the result will be an empty shape.
 
   Examples:
 
@@ -29557,11 +29557,11 @@ This version of the operator has been available since version 23 of the default
   The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
   If the end axis is omitted, the axes upto the last one will be included.
   Negative axes indicate counting back from the last axis.
-  Note that axes will be clamped to the range [0, r-1], where r is the
+  Note that axes will be clamped to the range [0, r], where r is the
   rank of the input tensor if they are out-of-range (after adding r in the case of
   negative axis). Thus, specifying any end value > r is equivalent to specifying an end
   value of r, and specifying any start value < -r is equivalent to specifying a start
-  value of 0.
+  value of 0. If start > end, the result will be an empty shape.
 
   Examples:
 
@@ -30811,11 +30811,11 @@ This version of the operator has been available since version 24 of the default
   The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
   If the end axis is omitted, the axes upto the last one will be included.
   Negative axes indicate counting back from the last axis.
-  Note that axes will be clamped to the range [0, r-1], where r is the
+  Note that axes will be clamped to the range [0, r], where r is the
   rank of the input tensor if they are out-of-range (after adding r in the case of
   negative axis). Thus, specifying any end value > r is equivalent to specifying an end
   value of r, and specifying any start value < -r is equivalent to specifying a start
-  value of 0.
+  value of 0. If start > end, the result will be an empty shape.
 
   Examples:
 

docs/Operators.md

@@ -32527,11 +32527,11 @@ expect(
   The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
   If the end axis is omitted, the axes upto the last one will be included.
   Negative axes indicate counting back from the last axis.
-  Note that axes will be clamped to the range [0, r-1], where r is the
+  Note that axes will be clamped to the range [0, r], where r is the
   rank of the input tensor if they are out-of-range (after adding r in the case of
   negative axis). Thus, specifying any end value > r is equivalent to specifying an end
   value of r, and specifying any start value < -r is equivalent to specifying a start
-  value of 0.
+  value of 0. If start > end, the result will be an empty shape.
 
   Examples:
 
@@ -32632,6 +32632,8 @@ test_shape("_start_1_end_2", x, start=1, end=2)
 test_shape("_clip_start", x, start=-10)
 
 test_shape("_clip_end", x, end=10)
+
+test_shape("_start_greater_than_end", x, start=2, end=1)
 ```
 
 </details>

docs/TestCoverage.md

@@ -23046,6 +23046,8 @@ test_shape("_start_1_end_2", x, start=1, end=2)
 test_shape("_clip_start", x, start=-10)
 
 test_shape("_clip_end", x, end=10)
+
+test_shape("_start_greater_than_end", x, start=2, end=1)
 ```
 
 </details>

onnx/backend/test/case/node/shape.py

@@ -56,3 +56,5 @@ def export() -> None:
         test_shape("_clip_start", x, start=-10)
 
         test_shape("_clip_end", x, end=10)
+
+        test_shape("_start_greater_than_end", x, start=2, end=1)

onnx/backend/test/data/node/test_shape_start_greater_than_end/model.onnx

@@ -0,0 +1 @@
+
B
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onnx/backend/test/data/node/test_shape_start_greater_than_end/test_data_set_0/input_0.pb

@@ -402,11 +402,11 @@ If start axis is omitted, the slice starts from axis 0.
 The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
 If the end axis is omitted, the axes upto the last one will be included.
 Negative axes indicate counting back from the last axis.
-Note that axes will be clamped to the range [0, r-1], where r is the
+Note that axes will be clamped to the range [0, r], where r is the
 rank of the input tensor if they are out-of-range (after adding r in the case of
 negative axis). Thus, specifying any end value > r is equivalent to specifying an end
 value of r, and specifying any start value < -r is equivalent to specifying a start
-value of 0.
+value of 0. If start > end, the result will be an empty shape.
 
 Examples:
 

onnx/backend/test/data/node/test_shape_start_greater_than_end/test_data_set_0/output_0.pb

@@ -1752,11 +1752,11 @@ If start axis is omitted, the slice starts from axis 0.
 The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
 If the end axis is omitted, the axes upto the last one will be included.
 Negative axes indicate counting back from the last axis.
-Note that axes will be clamped to the range [0, r-1], where r is the
+Note that axes will be clamped to the range [0, r], where r is the
 rank of the input tensor if they are out-of-range (after adding r in the case of
 negative axis). Thus, specifying any end value > r is equivalent to specifying an end
 value of r, and specifying any start value < -r is equivalent to specifying a start
-value of 0.
+value of 0. If start > end, the result will be an empty shape.
 
 Examples:
 
@@ -7553,11 +7553,11 @@ If start axis is omitted, the slice starts from axis 0.
 The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
 If the end axis is omitted, the axes upto the last one will be included.
 Negative axes indicate counting back from the last axis.
-Note that axes will be clamped to the range [0, r-1], where r is the
+Note that axes will be clamped to the range [0, r], where r is the
 rank of the input tensor if they are out-of-range (after adding r in the case of
 negative axis). Thus, specifying any end value > r is equivalent to specifying an end
 value of r, and specifying any start value < -r is equivalent to specifying a start
-value of 0.
+value of 0. If start > end, the result will be an empty shape.
 
 Examples:
 
@@ -7656,11 +7656,11 @@ If start axis is omitted, the slice starts from axis 0.
 The end axis, if specified, is exclusive (and the returned value will not include the size of that axis).
 If the end axis is omitted, the axes upto the last one will be included.
 Negative axes indicate counting back from the last axis.
-Note that axes will be clamped to the range [0, r-1], where r is the
+Note that axes will be clamped to the range [0, r], where r is the
 rank of the input tensor if they are out-of-range (after adding r in the case of
 negative axis). Thus, specifying any end value > r is equivalent to specifying an end
 value of r, and specifying any start value < -r is equivalent to specifying a start
-value of 0.
+value of 0. If start > end, the result will be an empty shape.
 
 Examples: