mir

Configuration

mir can be configured through CLI flags and an optional XML config file (mir.xml). There is no required config file — mir works out of the box with sensible defaults.

Config file (`mir.xml`)

When run, mir searches upward from the current directory for mir.xml. If no mir.xml is found, it falls back to psalm.xml (Psalm compatibility). You can also point to a config file explicitly with -c.

Example `mir.xml`

<?xml version="1.0"?>
<mir xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" errorLevel="3">
  <projectFiles>
    <directory name="src" />
    <directory name="lib" />
  </projectFiles>

  <ignoreFiles>
    <directory name="vendor" />
  </ignoreFiles>

  <issueHandlers>
    <UndefinedVariable errorLevel="suppress" />
    <PossiblyNullReference errorLevel="warning" />
  </issueHandlers>

  <phpVersion>8.2</phpVersion>
  <findUnusedCode>true</findUnusedCode>
  <findUnusedVariables>true</findUnusedVariables>
</mir>

Config file fields

Field	Description
`errorLevel` attribute	Global strictness: `1` (errors only) to `8` (lenient). Default: `2`.
`<projectFiles>`	Source directories to analyze.
`<ignoreFiles>`	Directories or files to exclude (e.g. `vendor/`).
`<issueHandlers>`	Per-issue-kind severity overrides (see below).
`<phpVersion>`	Target PHP version string, e.g. `8.2`.
`<findUnusedCode>`	Enable dead-code detection (`true`/`false`). Default: `false`.
`<findUnusedVariables>`	Enable unused-variable checking (`true`/`false`). Default: `false`.

Issue handlers

Each child element of <issueHandlers> is an issue kind name with an errorLevel attribute:

Level	Effect
`error`	Treat as error (exit code 1)
`warning`	Treat as warning
`info`	Treat as info (only shown with `--show-info` or `errorLevel >= 7`)
`suppress`	Silence the issue entirely

<issueHandlers>
  <UndefinedMethod errorLevel="suppress" />
  <InvalidArgument errorLevel="warning" />
</issueHandlers>

CLI flags

CLI flags always override values from the config file.

Flag	Default	Description
`-c, --config <FILE>`	auto	Config file path. Auto-discovers `mir.xml` / `psalm.xml` if omitted.
`--baseline <FILE>`	auto	Suppress known issues from a baseline XML. Auto-discovers `psalm-baseline.xml`.
`--set-baseline [FILE]`	`psalm-baseline.xml`	Write all current issues to a baseline file and exit.
`--update-baseline`	off	Remove resolved issues from the baseline.
`--ignore-baseline`	off	Report all issues, ignoring the baseline.
`--error-level <1-8>`	from config	Override global error level.
`--php-version <X.Y>`	from config	Target PHP version (e.g. `8.2`).
`--format <FORMAT>`	`text`	Output format: `text`, `json`, `github`, `junit`, `sarif`.
`--show-info`	off	Include info-level issues (redundancies, style).
`-j, --threads <N>`	CPU count	Parallelism.
`--cache-dir <DIR>`	off	Enable incremental cache in `DIR`.
`--stats`	off	Print file count, error/warning totals, elapsed time.
`-v, --verbose`	off	Print per-file issue counts.
`-q, --quiet`	off	Suppress all output; use exit code only.
`--no-progress`	off	Disable the progress bar.

Baselines

A baseline file records known issues so that they are suppressed on future runs. This lets you adopt mir incrementally — silence pre-existing issues and focus on new ones as they are introduced.

Baseline files use Psalm’s XML format, so an existing psalm-baseline.xml works directly.

Baseline workflow

# 1. Generate a baseline from the current issues (first adoption)
mir --set-baseline psalm-baseline.xml src/

# 2. Subsequent runs suppress baselined issues automatically
#    (psalm-baseline.xml in the cwd is picked up automatically)
mir src/

# 3. Explicitly point to a baseline in a non-standard location
mir --baseline path/to/my-baseline.xml src/

# 4. After fixing issues, shrink the baseline (removes resolved entries)
mir --update-baseline src/

# 5. Temporarily ignore the baseline to see all issues
mir --ignore-baseline src/

Common configurations

Basic project with vendor exclusion

<?xml version="1.0"?>
<mir errorLevel="3">
  <projectFiles>
    <directory name="src" />
  </projectFiles>
  <ignoreFiles>
    <directory name="vendor" />
  </ignoreFiles>
</mir>

CI pipeline (GitHub Actions)

# In .github/workflows/mir.yml:
mir --format github --no-progress --baseline psalm-baseline.xml src/

Strict analysis (errors only, no warnings)

mir --error-level 1 src/

Target a specific PHP version

mir --php-version 8.1 src/

Suppress a noisy issue kind project-wide

<issueHandlers>
  <UndefinedMethod errorLevel="suppress" />
</issueHandlers>

Incremental analysis with caching

mir --cache-dir .mir-cache src/

mir