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Remove `ImportNameless` bytecode by ShaharNaveh · Pull Request #6325 · RustPython/RustPython

youknowone

Walkthrough

The changes remove the ImportNameless instruction variant from the import handling pipeline. The codegen module now unconditionally emits ImportName with an empty string for the module name when no module is present, eliminating the previous conditional branching between ImportName and ImportNameless.

Changes

Cohort / File(s) Summary
Import Instruction Removal
crates/compiler-core/src/bytecode.rs		 Removed ImportNameless enum variant from Instruction and deleted related branches in stack_effect and fmt_dis functions.
Codegen Compilation Update
crates/codegen/src/compile.rs		 Replaced conditional emission of ImportName or ImportNameless with uniform ImportName emission; uses empty string as module name when module is absent.
VM Execution Path Removal
crates/vm/src/frame.rs		 Removed ImportNameless instruction branch from ExecutingFrame::execute_instruction.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

  • Verify that empty string module names in the codegen change are correctly handled throughout the runtime execution
  • Confirm all references to ImportNameless have been removed across the codebase
  • Validate that the uniform ImportName approach with empty module strings doesn't introduce edge case regressions

Possibly related PRs

Suggested reviewers

  • youknowone

Poem

🐰 A nameless import hops away,
One path remains, no more the fray,
Empty strings now do the trick,
Clean and simple, very slick!
The code flows smooth, no branches tangled,
Import logic, nicely wrangled. ✨

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title 'Remove ImportNameless bytecode' directly and specifically summarizes the main change: removing the ImportNameless bytecode variant and its associated handling across three files.
Docstring Coverage ✅ Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
✨ Finishing touches
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📥 Commits

Reviewing files that changed from the base of the PR and between d287d1e and a8a489e.

📒 Files selected for processing (3)
  • crates/codegen/src/compile.rs (1 hunks)
  • crates/compiler-core/src/bytecode.rs (1 hunks)
  • crates/vm/src/frame.rs (0 hunks)
💤 Files with no reviewable changes (1)
  • crates/vm/src/frame.rs
🧰 Additional context used
📓 Path-based instructions (1)
**/*.rs

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

**/*.rs: Follow the default rustfmt code style by running cargo fmt to format Rust code
Always run clippy to lint Rust code (cargo clippy) before completing tasks and fix any warnings or lints introduced by changes
Follow Rust best practices for error handling and memory management
Use the macro system (pyclass, pymodule, pyfunction, etc.) when implementing Python functionality in Rust

Files:

  • crates/compiler-core/src/bytecode.rs
  • crates/codegen/src/compile.rs
🧬 Code graph analysis (1)
crates/codegen/src/compile.rs (3)
crates/derive-impl/src/pymodule.rs (1)
  • module_name (437-439)
crates/derive-impl/src/util.rs (1)
  • module (428-457)
crates/codegen/src/ir.rs (1)
  • idx (35-37)
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🔇 Additional comments (2)
crates/codegen/src/compile.rs (1)

1354-1365: Unified ImportName handling for nameless from imports looks correct

Using module.as_ref().map_or("", |s| s.as_str()) and always emitting ImportName keeps the stack contract identical to CPython: level and from_list are consumed and the module object is pushed, with nameless from-imports represented by an empty-string entry in co_names. This removes the need for a separate ImportNameless opcode while preserving observable behavior, assuming the VM’s ImportName now treats "" the same way the old nameless variant did.

Please double‑check that the updated ImportName execution path in crates/vm/src/frame.rs explicitly handles the empty‑string name in the same way the removed ImportNameless variant did, and that there are tests (or disassembly snapshots) covering from . import x / from ... import x cases.

crates/compiler-core/src/bytecode.rs (1)

1604-1611: ImportName stack effect -1 matches its two-arg import usage

Defining ImportName { .. } => -1 is consistent with the compiler pushing level and from_list before the opcode and expecting a single module object afterward (net 2 pops, 1 push). Combined with ImportFrom { .. } => 1, this keeps the import stack discipline coherent after removing ImportNameless.

If you have a stack‑effect test or disassembly snapshot suite for import opcodes, it’s worth re‑running/expanding it to confirm the computed effects for import x and from ... import y still match CPython’s behavior.

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