Add custom Credo check for conn shadowing in tests

Detects `conn = get(conn, ...)` patterns and directs to
refactor_conn_aliasing.sh for automatic fixing.
This commit is contained in:
Willem van den Ende 2026-03-20 21:17:42 +00:00
parent 9426582abc
commit 505a2d0bd6
2 changed files with 270 additions and 0 deletions

226
app/.credo.exs Normal file
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# This file contains the configuration for Credo and you are probably reading
# this after creating it with `mix credo.gen.config`.
#
# If you find anything wrong or unclear in this file, please report an
# issue on GitHub: https://github.com/rrrene/credo/issues
#
%{
#
# You can have as many configs as you like in the `configs:` field.
configs: [
%{
#
# Run any config using `mix credo -C <name>`. If no config name is given
# "default" is used.
#
name: "default",
#
# These are the files included in the analysis:
files: %{
#
# You can give explicit globs or simply directories.
# In the latter case `**/*.{ex,exs}` will be used.
#
included: [
"lib/",
"src/",
"test/",
"web/",
"apps/*/lib/",
"apps/*/src/",
"apps/*/test/",
"apps/*/web/"
],
excluded: [~r"/_build/", ~r"/deps/", ~r"/node_modules/"]
},
#
# Load and configure plugins here:
#
plugins: [],
#
# If you create your own checks, you must specify the source files for
# them here, so they can be loaded by Credo before running the analysis.
#
requires: ["lib/firehose/checks/"],
#
# If you want to enforce a style guide and need a more traditional linting
# experience, you can change `strict` to `true` below:
#
strict: false,
#
# To modify the timeout for parsing files, change this value:
#
parse_timeout: 5000,
#
# If you want to use uncolored output by default, you can change `color`
# to `false` below:
#
color: true,
#
# You can customize the parameters of any check by adding a second element
# to the tuple.
#
# To disable a check put `false` as second element:
#
# {Credo.Check.Design.DuplicatedCode, false}
#
checks: %{
enabled: [
#
## Consistency Checks
#
{Credo.Check.Consistency.ExceptionNames, []},
{Credo.Check.Consistency.LineEndings, []},
{Credo.Check.Consistency.ParameterPatternMatching, []},
{Credo.Check.Consistency.SpaceAroundOperators, []},
{Credo.Check.Consistency.SpaceInParentheses, []},
{Credo.Check.Consistency.TabsOrSpaces, []},
#
## Design Checks
#
# You can customize the priority of any check
# Priority values are: `low, normal, high, higher`
#
{Credo.Check.Design.AliasUsage,
[priority: :low, if_nested_deeper_than: 2, if_called_more_often_than: 0]},
{Credo.Check.Design.TagFIXME, []},
# You can also customize the exit_status of each check.
# If you don't want TODO comments to cause `mix credo` to fail, just
# set this value to 0 (zero).
#
{Credo.Check.Design.TagTODO, [exit_status: 2]},
#
## Readability Checks
#
{Credo.Check.Readability.AliasOrder, []},
{Credo.Check.Readability.FunctionNames, []},
{Credo.Check.Readability.LargeNumbers, []},
{Credo.Check.Readability.MaxLineLength, [priority: :low, max_length: 120]},
{Credo.Check.Readability.ModuleAttributeNames, []},
{Credo.Check.Readability.ModuleDoc, []},
{Credo.Check.Readability.ModuleNames, []},
{Credo.Check.Readability.ParenthesesInCondition, []},
{Credo.Check.Readability.ParenthesesOnZeroArityDefs, []},
{Credo.Check.Readability.PipeIntoAnonymousFunctions, []},
{Credo.Check.Readability.PredicateFunctionNames, []},
{Credo.Check.Readability.PreferImplicitTry, []},
{Credo.Check.Readability.RedundantBlankLines, []},
{Credo.Check.Readability.Semicolons, []},
{Credo.Check.Readability.SpaceAfterCommas, []},
{Credo.Check.Readability.StringSigils, []},
{Credo.Check.Readability.TrailingBlankLine, []},
{Credo.Check.Readability.TrailingWhiteSpace, []},
{Credo.Check.Readability.UnnecessaryAliasExpansion, []},
{Credo.Check.Readability.VariableNames, []},
{Credo.Check.Readability.WithSingleClause, []},
#
## Refactoring Opportunities
#
{Credo.Check.Refactor.Apply, []},
{Credo.Check.Refactor.CondStatements, []},
{Credo.Check.Refactor.CyclomaticComplexity, []},
{Credo.Check.Refactor.FilterCount, []},
{Credo.Check.Refactor.FilterFilter, []},
{Credo.Check.Refactor.FunctionArity, []},
{Credo.Check.Refactor.LongQuoteBlocks, []},
{Credo.Check.Refactor.MapJoin, []},
{Credo.Check.Refactor.MatchInCondition, []},
{Credo.Check.Refactor.NegatedConditionsInUnless, []},
{Credo.Check.Refactor.NegatedConditionsWithElse, []},
{Credo.Check.Refactor.Nesting, []},
{Credo.Check.Refactor.RedundantWithClauseResult, []},
{Credo.Check.Refactor.RejectReject, []},
{Credo.Check.Refactor.UnlessWithElse, []},
{Credo.Check.Refactor.WithClauses, []},
#
## Warnings
#
{Credo.Check.Warning.ApplicationConfigInModuleAttribute, []},
{Credo.Check.Warning.BoolOperationOnSameValues, []},
{Credo.Check.Warning.Dbg, []},
{Credo.Check.Warning.ExpensiveEmptyEnumCheck, []},
{Credo.Check.Warning.IExPry, []},
{Credo.Check.Warning.IoInspect, []},
{Credo.Check.Warning.MissedMetadataKeyInLoggerConfig, []},
{Credo.Check.Warning.OperationOnSameValues, []},
{Credo.Check.Warning.OperationWithConstantResult, []},
{Credo.Check.Warning.RaiseInsideRescue, []},
{Credo.Check.Warning.SpecWithStruct, []},
{Credo.Check.Warning.StructFieldAmount, []},
{Credo.Check.Warning.UnsafeExec, []},
{Credo.Check.Warning.UnusedEnumOperation, []},
{Credo.Check.Warning.UnusedFileOperation, []},
{Credo.Check.Warning.UnusedKeywordOperation, []},
{Credo.Check.Warning.UnusedListOperation, []},
{Credo.Check.Warning.UnusedMapOperation, []},
{Credo.Check.Warning.UnusedPathOperation, []},
{Credo.Check.Warning.UnusedRegexOperation, []},
{Credo.Check.Warning.UnusedStringOperation, []},
{Credo.Check.Warning.UnusedTupleOperation, []},
{Credo.Check.Warning.WrongTestFilename, []},
#
## Custom Checks
#
{Firehose.Checks.NoConnShadowing, []}
],
disabled: [
#
# Checks scheduled for next check update (opt-in for now)
{Credo.Check.Refactor.UtcNowTruncate, []},
#
# Controversial and experimental checks (opt-in, just move the check to `:enabled`
# and be sure to use `mix credo --strict` to see low priority checks)
#
{Credo.Check.Consistency.MultiAliasImportRequireUse, []},
{Credo.Check.Consistency.UnusedVariableNames, []},
{Credo.Check.Design.DuplicatedCode, []},
{Credo.Check.Design.SkipTestWithoutComment, []},
{Credo.Check.Readability.AliasAs, []},
{Credo.Check.Readability.BlockPipe, []},
{Credo.Check.Readability.ImplTrue, []},
{Credo.Check.Readability.MultiAlias, []},
{Credo.Check.Readability.NestedFunctionCalls, []},
{Credo.Check.Readability.OneArityFunctionInPipe, []},
{Credo.Check.Readability.OnePipePerLine, []},
{Credo.Check.Readability.SeparateAliasRequire, []},
{Credo.Check.Readability.SingleFunctionToBlockPipe, []},
{Credo.Check.Readability.SinglePipe, []},
{Credo.Check.Readability.Specs, []},
{Credo.Check.Readability.StrictModuleLayout, []},
{Credo.Check.Readability.WithCustomTaggedTuple, []},
{Credo.Check.Refactor.ABCSize, []},
{Credo.Check.Refactor.AppendSingleItem, []},
{Credo.Check.Refactor.CondInsteadOfIfElse, []},
{Credo.Check.Refactor.DoubleBooleanNegation, []},
{Credo.Check.Refactor.FilterReject, []},
{Credo.Check.Refactor.IoPuts, []},
{Credo.Check.Refactor.MapMap, []},
{Credo.Check.Refactor.ModuleDependencies, []},
{Credo.Check.Refactor.NegatedIsNil, []},
{Credo.Check.Refactor.PassAsyncInTestCases, []},
{Credo.Check.Refactor.PipeChainStart, []},
{Credo.Check.Refactor.RejectFilter, []},
{Credo.Check.Refactor.VariableRebinding, []},
{Credo.Check.Warning.LazyLogging, []},
{Credo.Check.Warning.LeakyEnvironment, []},
{Credo.Check.Warning.MapGetUnsafePass, []},
{Credo.Check.Warning.MixEnv, []},
{Credo.Check.Warning.UnsafeToAtom, []}
# {Credo.Check.Warning.UnusedOperation, [{MyMagicModule, [:fun1, :fun2]}]}
# {Credo.Check.Refactor.MapInto, []},
#
# Custom checks can be created using `mix credo.gen.check`.
#
]
}
}
]
}

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defmodule Firehose.Checks.NoConnShadowing do
use Credo.Check,
base_priority: :normal,
category: :readability,
explanations: [
check: """
Conn shadowing (`conn = get(conn, ...)`) makes Phoenix controller tests
noisy. Use pipe chains instead:
body = conn |> get("/path") |> html_response(200)
Run `./refactor_conn_aliasing.sh <file>` to fix automatically.
"""
]
@http_verbs ~w(get post put patch delete head options)a
@impl true
def run(%SourceFile{} = source_file, params) do
issue_meta = IssueMeta.for(source_file, params)
source_file
|> Credo.Code.prewalk(&traverse(&1, &2, issue_meta))
|> Enum.reverse()
end
defp traverse({:=, meta, [{:conn, _, _}, {verb, _, [{:conn, _, _} | _]}]} = ast, issues, issue_meta)
when verb in @http_verbs do
issue = issue_for(issue_meta, meta[:line], verb)
{ast, [issue | issues]}
end
defp traverse(ast, issues, _issue_meta) do
{ast, issues}
end
defp issue_for(issue_meta, line_no, verb) do
format_issue(
issue_meta,
message: "Conn shadowing detected (`conn = #{verb}(conn, ...)`). Run `./refactor_conn_aliasing.sh <file>` to fix.",
line_no: line_no
)
end
end