Warn instead of aborting when get_property is given an empty collection

[akashlevy]

Reapplies #80, which was reverted in #81 because it dropped the diagnostic entirely. Same fix,
except the empty-collection case now warns rather than going silent.

Problem

get_property aborts with Error 2200: get_property object is null. whenever its object
argument is an empty collection. Every get_*/all_* command encodes "nothing matched" as
the empty string, in both list mode and collections mode, so this fires on ordinary code:

set outnets [get_nets -quiet [get_property [all_outputs] name]]

That line is the first line of Preqorsor's power-characterization SDC. On a carved-out block
with no output ports, [all_outputs] is empty and the error killed the interpreter. In one
production run all 16 STA shards died there, losing the timing/power data for ~4100 of 4630
cells about 6.5 hours in.

Fix

Warn and return an empty list. The branch immediately below already maps the property over
every element of a collection, and an empty collection is simply the zero-element case of
that: no objects, no property values. An unmatched lookup is worth telling the user about,
but it should not take the script down with it.

Three details worth reviewing:

• The warning reuses id 2200, the id this used to error with, so anyone already running
  suppress_msg 2200 keeps the behavior they asked for.
• -quiet silences it per call. The flag was already parsed and already suppressed the
  sibling "not found" diagnostic on the -object_type path; it is now documented, which it
  previously was not.
• Non-empty behavior is untouched: one object still yields a bare value, many still yield a
  list.

Test

New test/get_property_empty.tcl links a design whose ports are all inputs and walks the
paths that used to abort: [all_outputs], empty get_ports/get_pins/get_cells/
get_clocks/get_lib_cells, a literal {} and "", the -object_type name-lookup path,
and the get_nets idiom from the SDC above. It pins one warning per call site, covers both
-quiet and suppress_msg 2200, and pins the unchanged non-empty results. Output is
identical with and without sta_enable_collections.

Test plan

• ./regression -j 12 fast — 110/110 pass
• ./regression -j 12 -collections fast — the same 4 tests fail before and after this
  change (all_inputs_filters, user_properties, vcd_begin_end_time,
  verilog_port_bundle_find_pin); collections mode is beta and CI does not run it
• The power SDC prologue that triggered the outage now warns once and runs to completion

Made with Cursor

[greptile-apps]

Greptile Summary

The PR changes get_property so an empty object collection emits suppressible warning 2200 and returns an empty list instead of aborting.

• Documents the existing -quiet option and applies it to the empty-object warning.
• Adds regression coverage for empty query results, literal empty arguments, warning suppression, collection mode, and unchanged non-empty behavior.
• Registers a small input-only Verilog fixture and its expected output in the public regression suite.

Confidence Score: 5/5

The PR appears safe to merge; no actionable correctness, compatibility, or security issues were identified.

The empty-object path initializes warning suppression correctly, returns the expected Tcl empty value, retains diagnostic ID compatibility, and is covered across both ordinary and collection modes without changing non-empty behavior.

Important Files Changed

Filename	Overview
tcl/Property.tcl	Converts the empty-object error into a suppressible warning and empty result while preserving non-empty property behavior.
test/get_property_empty.tcl	Exercises empty results across supported object types, suppression mechanisms, the motivating nested-command case, and non-empty results.
test/get_property_empty.ok	Pins warning counts and returned values for the new regression coverage.
test/get_property_empty.v	Provides an input-only linked design whose output-port collection is empty.
test/regression_vars.tcl	Adds the new test to the public regression suite.

_{Reviews (1): Last reviewed commit: "Warn instead of aborting when get_proper..." | Re-trigger Greptile}