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Find duplicate code

Recipe IDio.moderne.prethink.quality.FindDuplicateCode

Artifactio.moderne.recipe:rewrite-prethink

Detect duplicate and likely-duplicate code across the codebase by AST-subtree fingerprinting and MinHash/LSH method alignment (zero AI). Reports Type-1 (exact), Type-2 (renamed), and Type-3 (gapped: inserted/removed/edited statements) clone groups ranked by the volume of code that would collapse if the duplication were refactored away.

Single recipeOpenRewriteModerne Proprietary License

Try in PlatformTry this recipe in the Moderne platform. Not a user yet? You’ll get a no-setup demo environment, with nothing to install or configure.

Options

12 parameters

12 optional

Parameter	Example	Type	Required
detectSimilarMethods	true	Boolean	Optional
Whether to also detect gapped (Type-3) clones between whole methods that share no long run of identical statements, by aligning MinHash/LSH-similar method pairs. Catches copy-edited methods the statement-run detector misses because it needs a run of identical statements to anchor. Defaults to true.
detectStatementSequences	true	Boolean	Optional
Whether to detect duplicated runs of consecutive statements (in addition to whole-subtree clones). Defaults to true.
detectType2	true	Boolean	Optional
Whether to detect renamed (Type-2) clones in addition to exact (Type-1) clones. Defaults to true.
gapBudget	1	Integer	Optional
Maximum number of statement edits (insertions, deletions, or substitutions) tolerated inside a statement-sequence clone (Type-3). 0 detects only exact/renamed runs; 1 (the default) also catches copy-paste-then-edit/insert/remove-one-statement. Higher values catch more divergent copies.
includeTestSources	false	Boolean	Optional
Whether to include test sources (paths under src/test). Defaults to false.
maxOccurrencesPerGroup	200	Integer	Optional
Cap on the number of individual occurrences reported per clone group. The true count is always reported; only the enumerated locations/rows are capped. Defaults to 200.
minNodes	75	Integer	Optional
Minimum number of AST nodes a subtree must contain to be considered for exact (Type-1) duplication. Larger values reduce noise. Defaults to 75.
minNodesType2	110	Integer	Optional
Minimum number of AST nodes a subtree must contain to be considered for renamed (Type-2) duplication. Should be at least the Type-1 minimum because anonymization is noisier. Defaults to 110.
minOccurrences	2	Integer	Optional
Minimum number of occurrences for a fragment to be reported as a clone group. Defaults to 2.
minStatements	5	Integer	Optional
Minimum number of consecutive statements that must match to seed a statement-sequence clone. Defaults to 5.
snippetMaxLines	40	Integer	Optional
Maximum number of lines of the representative fragment to include in the snippet. Defaults to 40.
suppressBoilerplate	true	Boolean	Optional
Whether to structurally suppress low-value boilerplate: getters/setters, equals/hashCode/toString, runs or blocks composed entirely of trivial data statements (constant declarations, map/collection population), and subtrees dominated by a large string-literal concatenation (embedded doc/JSON/prompt blobs). Suppressed fragments are still descended into, so genuine clones nested inside them are still found. Defaults to true.

Usage

Run this recipe

This recipe has no required configuration options. Users of Moderne can run it via the Moderne CLI.

You will need to have configured the Moderne CLI on your machine before you can run the following command.

shell

mod run . --recipe FindDuplicateCode

If the recipe is not available locally, then you can install it using:

mod config recipes jar install io.moderne.recipe:rewrite-prethink:0.9.0

Data tables

Duplicate code

io.moderne.prethink.table.DuplicateCode

Groups of duplicated code detected across the codebase by AST-subtree fingerprinting. One row per clone group; sort by redundant volume to surface the highest-value refactoring targets.

Column	Description
Clone group id	Stable identifier for the clone group (hex of the anonymized structural fingerprint). Join key to the duplicate code occurrences data table.
Clone type	TYPE_1 (identical modulo whitespace and comments) or TYPE_2 (identical structure with renamed identifiers and literals).
Duplicate count	Total number of occurrences of this fragment across the codebase.
Source path	Path of the representative (lexicographically-first) occurrence of the clone group.
Snippet	The duplicated code, printed from the representative occurrence and truncated for large fragments.
Lines	Line count of the representative fragment.
Node mass	Number of AST nodes in the representative fragment; the internal precision gate.
Redundant volume	Lines multiplied by (duplicate count minus one): the number of lines that would collapse if the duplication were refactored to a single copy. Sort by this to surface the highest-value targets.
Duplicate locations	Newline-separated list of every occurrence's source path with enclosing type and member. Capped for very large groups, with a true-count line.

Duplicate code occurrences

io.moderne.prethink.table.DuplicateCodeOccurrences

One row per individual occurrence of a duplicated fragment, with the machine coordinates a remediation recipe needs to locate and converge each clone. Join to the duplicate code data table on clone group id.

Column	Description
Clone group id	Identifier of the clone group this occurrence belongs to. Join key to the duplicate code data table.
Clone type	TYPE_1 or TYPE_2.
Occurrence role	REPRESENTATIVE (the canonical copy reported in the duplicate code table) or DUPLICATE.
Source path	Path of the source file containing this occurrence.
Enclosing type	Fully qualified name of the class enclosing this occurrence, if any.
Enclosing member	Name of the method enclosing this occurrence, if any.
Node id	The AST node's stable identifier (UUID). The primary machine coordinate a remediation recipe uses to locate this occurrence within the LST.
Start line	Best-effort absolute start line of the occurrence; -1 when not available.
End line	Best-effort absolute end line of the occurrence; -1 when not available.
Line count	Number of lines in the occurrence fragment.
Node mass	Number of AST nodes in the occurrence fragment.
Strict fingerprint	Hex of the 128-bit exact (Type-1) structural fingerprint.
Anon fingerprint	Hex of the 128-bit anonymized (Type-2) structural fingerprint.

Source files that had results

org.openrewrite.table.SourcesFileResults

Source files that were modified by the recipe run.

Column	Description
Source path before the run	The source path of the file before the run. null when a source file was created during the run.
Source path after the run	A recipe may modify the source path. This is the path after the run. null when a source file was deleted during the run.
Parent of the recipe that made changes	In a hierarchical recipe, the parent of the recipe that made a change. Empty if this is the root of a hierarchy or if the recipe is not hierarchical at all.
Recipe that made changes	The specific recipe that made a change.
Estimated time saving	An estimated effort that a developer to fix manually instead of using this recipe, in unit of seconds.
Cycle	The recipe cycle in which the change was made.

Source files that had search results

org.openrewrite.table.SearchResults

Search results that were found during the recipe run.

Column	Description
Source path of search result before the run	The source path of the file with the search result markers present.
Source path of search result after run the run	A recipe may modify the source path. This is the path after the run. null when a source file was deleted during the run.
Result	The trimmed printed tree of the LST element that the marker is attached to.
Description	The content of the description of the marker.
Recipe that added the search marker	The specific recipe that added the Search marker.

Source files that errored on a recipe

org.openrewrite.table.SourcesFileErrors

The details of all errors produced by a recipe run.

Column	Description
Source path	The file that failed to parse.
Recipe that made changes	The specific recipe that made a change.
Stack trace	The stack trace of the failure.

Recipe performance

org.openrewrite.table.RecipeRunStats

Statistics used in analyzing the performance of recipes.

Column	Description
The recipe	The recipe whose stats are being measured both individually and cumulatively.
Source file count	The number of source files the recipe ran over.
Source file changed count	The number of source files which were changed in the recipe run. Includes files created, deleted, and edited.
Cumulative scanning time (ns)	The total time spent across the scanning phase of this recipe.
Max scanning time (ns)	The max time scanning any one source file.
Cumulative edit time (ns)	The total time spent across the editing phase of this recipe.
Max edit time (ns)	The max time editing any one source file.