Fix #1576 max width in qasm (#1653)

* fix maxwidth

* reduce testcase

* clean up

* Add  to  to changelog

pytket/docs/changelog.rst

@@ -14,6 +14,8 @@ Fixes:
 * Fix `symbol_substitution` not preserving opgroups.
 * Remove hardware inefficient circuit construction in `_tk1_to_rzsx`
 * Support converting conditional `RangePredicate`s to QASM.
+* Fix `maxwidth` parameter of `circuit_from_qasm_str`
+* Add `scratch_reg_resize_pass` to `circuit_from_qasm_str`
 
 1.34.0 (October 2024)
 ---------------------

pytket/pytket/qasm/qasm.py

@@ -88,7 +88,12 @@
     create_logic_exp,
 )
 from pytket.qasm.grammar import grammar
-from pytket.passes import AutoRebase, DecomposeBoxes, RemoveRedundancies
+from pytket.passes import (
+    AutoRebase,
+    DecomposeBoxes,
+    RemoveRedundancies,
+    scratch_reg_resize_pass,
+)
 from pytket.wasm import WasmFileHandler
 
 
@@ -1028,7 +1033,11 @@ def circuit_from_qasm_str(
     cast(CircuitTransformer, g_parser.options.transformer)._reset_context(
         reset_wasm=False
     )
-    return Circuit.from_dict(g_parser.parse(qasm_str))  # type: ignore[arg-type]
+
+    circ = Circuit.from_dict(g_parser.parse(qasm_str))  # type: ignore[arg-type]
+    cpass = scratch_reg_resize_pass(maxwidth)
+    cpass.apply(circ)
+    return circ
 
 
 def circuit_from_qasm_io(

pytket/tests/qasm_test.py

@@ -94,6 +94,26 @@ def test_qasm_correct() -> None:
     assert str(coms3) == correct_str3
 
 
+def test_long_registers() -> None:
+    fname = str(curr_file_path / "qasm_test_files/longreg.qasm")
+    c = circuit_from_qasm(fname, maxwidth=64)
+    assert c.n_qubits == 0
+    assert c.n_bits == 79
+    assert len(c.c_registers) == 5
+    for creg in c.c_registers:
+        assert creg.size <= 64
+
+
+def test_long_registers_2() -> None:
+    fname = str(curr_file_path / "qasm_test_files/longreg.qasm")
+    c = circuit_from_qasm(fname, maxwidth=100)
+    assert c.n_qubits == 0
+    assert c.n_bits == 79
+    assert len(c.c_registers) == 4
+    for creg in c.c_registers:
+        assert creg.size <= 100
+
+
 def test_qasm_qubit() -> None:
     with pytest.raises(RuntimeError) as errorinfo:
         fname = str(curr_file_path / "qasm_test_files/test2.qasm")
@@ -602,7 +622,8 @@ def test_scratch_bits_filtering() -> None:
     creg {_TEMP_BIT_NAME}_1[32];
     {_TEMP_BIT_NAME}[0] = (a[0] ^ b[0]);
     if({_TEMP_BIT_NAME}[0]==1) x q[0];
-    """
+    """,
+        maxwidth=64,
     )
     assert c.get_c_register(_TEMP_BIT_NAME)
     assert c.get_c_register(f"{_TEMP_BIT_NAME}_1")

pytket/tests/qasm_test_files/longreg.qasm

@@ -0,0 +1,83 @@
+OPENQASM 2.0;
+include "hqslib1.inc";
+
+creg a[1];
+creg b[1];
+creg c[1];
+
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;
+if(c!=0) a = b;