MISS_HIT 0.9.30-dev Code Metrics
MISS_HIT includes a simple code metric tool (mh_metric). It computes code metrics and complains if the metrics exceed acceptable levels.


Using MISS_HIT Metric

This tool works exactly the same as the style checker, and re-uses the same configuration files and mechanism.
To compute metrics on a set of files:
$ mh_metric my_file.m my_model.slx
MH Metric fully supports MATLAB code embedded inside Simulink models. (Unlike MH Style, there is no extra flag needed.)
To compute metrics for all files in a directory tree:
$ mh_metric src/
To produce metrics in the current directory tree:
$ mh_metric
Metrics are reported on standard out. You can also produce a JSON report, HTML report or write the metrics to a text-file:
$ mh_metrics src --text=metrics.txt
$ mh_metrics src --html=metrics.html
$ mh_metrics src --json=metrics.json
In a future release more formats (e.g. csv, etc.) will be supported.
Inside a CI environment, this produces too much output. Instead you can use the ci option for this:
$ mh_metrics src --ci
This mode will not produce an overall report, instead only report violations.

Enabling and disabling metrics

To turn off limit checking for a specific metric (the default for all metrics), you can use the report directive in the config files:
metric "npath": report
To completely disable a metric (it will not be measured, nor turn up in the final report), you can use the disable directive:
metric "npath": disable
To completely disable or enable all metrics (useful for large projects using complicated hierarchical configurations), you can use the wildcard directive with report and disable:
metric *: disable
metric *: report

Configuring and enforcing limits

As indicated above, by default metrics are just reported. However you canb also enforce limits on any metric. For example, to limit the number of paths for each function, you add this this to your configuration file:
metric "npath": limit 5
As with other configuration, these limits propagate to sub-directories. You can change these limits on a more local bases (just like with style rules).
In the description for each metric below, the name of the metric to use in config files is included in parenthesis.



Metrics can be justified by placing a justification pragma at the level of scope where the violation occurs. Please refer to MISS_HIT Pragmas for a full description of all pragmas understood by MISS_HIT.
For example:
%| pragma Justify (metric, "npath", "can't be refactored");
Longer justifications can be broken up into several lines:
%| pragma Justify (metric, "npath",
%|                 "this cannot be refactored " +
%|                 "and I am going to tell you " +
%|                 "why not...");
Justifications that are useless generate a warning.

Integration with issue-tracking systems

A special configuration directive regex_tickets can be placed in the MISS_HIT configuration file. When set, this allows MISS_HIT to extract ticket identifiers from justifications, which in turn appear in a special section in the report.
For example, this is how you can integrate with JIRA:
regex_tickets: "\b[A-Z]{3,}-[0-9]+\b"
Or GitHub issues:
regex_tickets: "\B#[0-9]+\b"
(Other regular expressions are left as an exercise to the reader.)
You can mention tickets freely in justification text, for example:
%| pragma Justify (metric, "cyc",
%|                 "to be fixed in POTATO-666 or KITTEN-42");
These then appear in the text or HTML report. This is helpful if you want to produce a report that mentions when things are going to be fixed.
The command-line option --ignore-justifications-with-tickets can be used to ignore any justifications that mention a ticket.


File metrics

These metrics are computed for each file.

Lines ("file_length")

The number of lines. Should be the equivalent to running the standard UNIX tool wc -l. This means comments and blank lines are counted.

Function metrics

These metrics are computed for each function, nested function, and method.

McCabe Cyclomatic Complexity ("cyc")

This measures the McCabe cyclomatic complexity. We have aimed for mlint compatibility, instead of doing it "right". Specifically this means:
  • Empty branches "count", even though they should not contribute, based on the original definition of the metric.
  • Exceptions are generally ignored. Specifically a try-catch block is treated like on flat block + one branch. This is not correct since every statement in a try block may create a jump.

Lines in function ("function_length")

The number of lines for each function. Note that adding together all lines of all functions will likely not add up to file_length due to blank lines and comments between functions.

Path count ("npath")

This approximates the number of paths through a function. This metric is based on NPATH and should be similar what other popular metric tools compute.
Note that this number can grow very large, very quickly, especially if you have a lot of sequential if blocks. Further note that this metric is neither an under-approximate or over-approximate, but a reasonable compromise.
Since the MATLAB language supports raising and catching exceptions (including exceptions further down the call tree) a safe over-approximate cannot be reasonably computed since every single line may raise multiple exceptions.

Maximum nesting of control structures ("cnest")

This measures the maximum level of nesting of control. Statements that are considered control statements are:
  • If statement
  • Switch statement
  • For loops
  • While loops
  • Exception handlers

Number of function parameters ("parameters")

This counts the number of parameters for each function. Both inputs and outputs are considered.

Number of direct globals ("globals")

This counts the number direct non-transitive globals for each function. In other words, it counts how many distinct things are mentioned by all global statements in a function.
For example this function has exactly one direct global:
function result = f1()
    global x
    result = x;
This function also has exactly one direct global. There is another global dependency via the call to f1, but it is hidden. The metric to measure all globals (direct and hidden) will be implemented once we have basic flow analysis working.
function result = f2()
    global y
    result = f1() + y;

Number of persistent variables ("persistent")

This counts the number of persistent variables for each function. In other words, it counts how many distinct things are mentioned by all persistent statements in a function.
Persistent variables make testing extremely difficult in MATLAB, more so than globals; so it is a really good idea to not have too many of them.
JSON Schema

JSON Report Schema


The purpose of the JSON report (unlike the text or HTML report) is to be easily machine-parseable. It is not intended for human consumption. The report schema is guaranteed to be stable between minor releases: i.e. function processing a report from a.b.* should also be able to process a report from a.c.* as long as c > b.



The entire report is a single JSON object containing two members:
  • metrics
  • worst_case


The metric member is a JSON object one member per file. The value of each member is another JSON object with the following members:
  • file_metrics
  • function_metrics


A file_metrics member is a JSON object containing members for each file metric (e.g. "file_length"). Each value is a metrics_result object described below.


A function_metrics member is a JSON object containing members for each function, which in turn are JSON objects containing members for each function metric (e.g. "cyc"). Each value is a metrics_result object described below.


A metrics_result is a JSON object containing the following members:
  • status - will be one of the following strings:
    • "measured only" - this metric was measured, but no limit was enforced
    • "checked: ok" - this metric was measured, and is equal to or below the configured limit
    • "checked: justified" - this metric was measured, and was above the configured limit; but a justification was supplied
    • "checked: fail" - this metric was measured, and was above the configured limit
  • measure - an integer indicating the measured value of the metric
  • limit - (only for checked metrics) - an integer indicating the configured limit
  • justification - (only for checked: justified metrics) - a string containing the justification supplied


The worst case table is JSON object where each member described a metric (function or file). The value of each is a list with augmented metric_result objects.

augmented metric_result

As metric_result (see above), but with on or two additional members:
  • file - a string indicating the file where the metric was measured
  • function - (only for function metrics) - a string indicating the function where the metric was measured