Highlight documentation

Syntax tests

Input files whose filenames start with syntax_test_ can contain column and state indicators in comment sections to test the highlight syntax recognition of the previous line. If such a test fails, highlight will print an error message and exit with FAILURE return value.

For UTF-8 encoded input, you need to set `--encoding=utf-8`. Otherwise the state indicator positions will not be calculated correctly.
Only the last 100 states of each input line are being tracked.

Test case notation

A test case is defined by two entities: column and expected state. The column is defined by ^ ("here") or < ("comment start / first column"). The state is defined by one of the following identifiers:

std: standard / no recognition
str: string
num: number
slc: single line comment
com: multiline comment
esc: escape character
ppc: preprocessor
pps: preprocessor string
opt: operator
ipl: interpolation
ws:  whitespace
kwX: keyword group X (X: a..z)

The state identifiers match the corresponding HTML output CSS class names.

Since release 3.47, the whitespace indicator `ws` is no longer exclusive. A test will succeed at a position with whitespace if the enclosing state is matched or if `ws` is tested specifically.

Add a leading `~` to an indicator to match any other state as success.

Example

#include <iostream>
#include "myheader"
// ^ ppc ^^^^^^^^^^ pps       1)  

int main() {
//  ^^^^ kwd                  2)  
/* comment comment comment  
 * <  com ^ ws     ^ com      3)
 */

    int var =   0x1234;
/*      ^^^ std ^    ^ num */
    //< kwb ^ opt             4)
    std::cout << "whatever: " << var <<   "\n";
//               ^          ^ str    ^^opt ^^ esc
    return 0;
    /*  <   kwa               5) */
}

this line contains a test for preprocessor and a preprocessor string. The ^ indicators point at the tested string sections of the previous line.
the keyword group kwd is checked (functions are highlighted as kwd in C syntax)
The < points to column 0 as the comment starts there. ws tests for whitespace.
A source code line can be tested with various test comments. Here the opt test looks for the operator two lines before.
< points at column 4, the beginning of the comment.

Running highlight with this file will not produce any additional output, as all tests pass. The exit status will be 0.

If you change the kwa in 5) to kwb (or any other state), highlight will print an error like this, and exit with status 1:

highlight: Could not validate file:
syntax_test_1.c line 17, column 4: got kwa instead of kwb

The highlight GUI will show the error messages in an error summary prompt.