I have created new Gradle project, added
apply plugin: 'antlr'
and
dependencies {
antlr "org.antlr:antlr4:4.5.3"
to build.gradle
.
Created src/main/antlr/test.g4
file with the following content
grammar test;
r : 'hello' ID;
ID : [a-z]+ ;
WS : [ \t\r\n]+ -> skip ;
But it doesn't work. No java source files generated (and no error occurred).
What I missed?
Project is here: https://github.com/dims12/AntlrGradlePluginTest2
UPDATE
I found my sample is actually works, but it put code into \build\generated-src
which I was not expecting :shame:
I will add onto other answers here.
Issue 1: Generated source files are placed in build/generated-src
folder.
I found this discussion, but the solution there (setting outputDirectory
property) is a bad idea. If you do gradle clean build
command, this will clear out your entire source directory. The discussion there gives a good explanation as to why you should not
the antlr generated sources are generated into a subdirectory of the "build" folder like all other artifacts, which are generated during the build. Furthermore your generated directory projectRoot/build/generated-src/antlr/main is added to the java sourceset definition to be sure its considered compileJava task. If you write the antlr generated source directly to the src/main/java folder you're polluting your source folder with output of your build process. ... Polluting your source folder during your build is an antipattern I think.
However, if you want to do this, you can add a gradle task to copy the generated files to the build directory.
generateGrammarSource << {
println "Copying generated grammar lexer/parser files to main directory."
copy {
from "${buildDir}/generated-src/antlr/main"
into "src/main/java"
}
}
Issue 2: Generated source files do not have package attribute set.
To solve this issue, add something like the following near the top of the grammar file:
@header {
package com.example.my.package;
}
What helped me is two things:
@header{ package com.example.something.antlrparser; }
to the grammar file directly after the grammar test;
declaration.src/main/antlr/com/example/something/antlrparser/grammar.g4
Now when I run the generateGrammarSource
gradle task, .java
files are generated in /build/generated-src/antlr/main/com/example/something/antlrparser/*.java
and they are automatically picked up by IntelliJ as well as compilable by gradle.
The build.gradle
file is just:
group 'com.example.something'
version '1.0-SNAPSHOT'
apply plugin: 'java'
apply plugin: 'antlr'
apply plugin: 'idea'
sourceCompatibility = 1.8
repositories {
mavenCentral()
}
dependencies {
testCompile group: 'junit', name: 'junit', version: '4.12'
antlr "org.antlr:antlr4:4.5" // use ANTLR version 4
}
Add this to your build.gradle
generateGrammarSource {
outputDirectory = file("src/main/java/com/example/parser")
}
add this to your grammar after your "grammar ";
@header {
package com.example.parser;
}
Tested and working with Java8 grammar from antlr example grammars
Additional Link(s):
Here is a short guide of the Antlr plugin from docs.gradle.org
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