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A developer hit the seam between Ruff's speed and Pylint's R0801 and wrote a single-purpose checker called Arid rather than keep waiting. No benchmarks published.
The Engineer · Build desk
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A developer working on a large Python project called Polaris reports that Ruff, which handles most of his linting and handles it quickly, does not detect duplicated blocks of code, and has released a single-purpose tool called Arid to cover that one job [1][2][3][9]. The consequence is worth stating plainly: according to the post, this is not a configuration you forgot to enable, because Ruff does not support project-wide duplicate-code detection today [4].
What does support it is Pylint. Its R0801 checker has been finding similar code for years, and the same capability ships as a standalone tool called symilar [5][6]. It can ignore comments, docstrings, imports, and function signatures while looking for repeated blocks [7]. It is also, on the author's project, slow enough that he stopped waiting for it [8]. That is the whole shape of the problem: the fast tool most teams now reach for has no duplicate detector, and the tool that has one is the general-purpose static-analysis system people moved away from for speed reasons. A rule category can disappear from a pipeline without anything turning red.
The reason this is not a weekend patch to Ruff is that duplicate detection on Python source is not text comparison. The post walks through two functions, save_customer and save_account, whose executable logic is identical but whose names and comments differ, and argues that if comments and signatures are excluded from the comparison they probably should count as duplicates [10]. Then the confounders stack up: docstrings, imports, blank lines, decorators, multiline function signatures, parenthesized expressions, different physical source ranges, and same-file duplicates that overlap one another [11]. Arid takes Pylint's R0801 as its definition of intent, finding repeated Python source while allowing those elements to be excluded, but explicitly does not reproduce Pylint's implementation [12].
The scope discipline is the interesting part for anyone maintaining a tool. Arid has one production responsibility, finding duplicated Python source code, and the author lists what it therefore does not do: no formatting, import sorting, type checking, complexity analysis, security scanning, or dead-code detection [13]. His stated rule is that if a feature naturally belongs in Ruff, it probably does not belong in Arid [14]. That flows through to structure. One language, so no generic language abstraction; one detector, so no detector hierarchy; no plugin system, no reporter registry, no dependency-injection framework, no async runtime, and no parser abstraction held in reserve for a parser swap that may never happen [15][16]. Parser-specific knowledge stays in the Python frontend, and everything downstream works on Arid-owned data structures rather than parser AST or token types [17]. The author frames this not as an argument against abstraction but as an argument for paying for it when a requirement exists [18].
What to watch. The post contains no runtime figures, no version numbers, and no measured comparison against symilar, so "Pylint was too slow" remains a qualitative claim from one project [19]. Anyone considering the swap should time symilar and Arid on their own tree before believing either. Also watch the author's own word choice: Ruff lacks this capability "today" [4], and a single-detector tool built to mirror R0801's intent is exactly the sort of thing that becomes redundant if the fast linter ever grows a duplicate checker of its own.
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Ranked by verification strength, evidence, and original report placement.
The author of the post was working on Polaris, described as a fairly large Python project, and running code-quality tools against it.
Ruff does not detect duplicated blocks of code, and the author says this is not an oversight in his configuration.
The author states that Ruff simply does not support project-wide duplicate-code detection today.
Pylint's R0801 checker has been finding similar code for years.
Pylint exposes the same duplicate-detection capability through a standalone tool called symilar.
Pylint's duplicate detection can ignore comments, docstrings, imports, and function signatures while looking for repeated blocks.
Evidence-backed comparisons of source perspectives and observed adoption signals. Read the methodology
Which Builder, Operator, and Investor concerns the observed source mix emphasized—not a truth score.
Evidence, demonstrated adoption, hype gap, incentives, and confidence are assessed independently, each on its own current evidence. How these are measured.
Single self-authored account, no measurements
All claims trace to one first-person dev.to post by the tool's author. Descriptive claims about Ruff's missing duplicate detection, Pylint's R0801/symilar, and Arid's own architecture are internally coherent and checkable in principle, but nothing in the cluster is independently corroborated and the central performance premise carries no numbers, versions, or datasets.
No adoption signal in cluster
The post announces that the author built Arid but supplies no repository, package, version, licence, download or user count, and no third-party deployment or usage disclosure. There is no basis to score adoption without inferring facts the source does not provide.
Performance premise outruns published proof
The framing — Pylint was too slow, so a new tool exists — is a comparative performance claim presented without a single measurement, and Arid's advantages are argued from scope and architecture rather than results. The overstatement is moderate rather than severe because the author is explicit about what Arid does not do, does not claim benchmark superiority, and concedes that judgment about duplicates remains the user's.
Author is the tool's creator, publishing on his own platform
The only source is written by Arid's author, on a self-publishing developer platform, and the narrative's purpose is to justify building and using his own tool at the expense of an incumbent (Pylint). That is a strong promotional and self-justification incentive with no editorial counterweight or independent voice in the cluster.
Low: one self-interested source, no verification path
Claims about Arid's own design can be taken at face value as statements of intent, and the Ruff/Pylint capability contrast is plausible and specific. But with a single self-authored source, no measurements, and no adoption evidence, confidence in anything beyond the author's description of his own choices stays low.
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1 article · August 16, 2026