Config parser (and loader)

docs/config.md

@@ -1943,3 +1943,52 @@ Some features can be enabled using the `nextflow.enable` and `nextflow.preview`
 : *Experimental: may change in a future release.*
 
 : When `true`, enables {ref}`topic channels <channel-topic>` feature.
+
+## Strict config mode
+
+:::{versionadded} 24.10.0
+:::
+
+Strict config mode is an alternative implementation of the config parser in Nextflow which enforces a stricter syntax. Whereas the existing parser interprets config files as Groovy scripts, which makes it overly powerful and error-prone, the strict config mode allows only a strict subset of Groovy syntax which is relevant to configuration.
+
+Strict config mode can be enabled by setting `NXF_ENABLE_STRICT_CONFIG=true`.
+
+The following statements are allowed in strict config mode:
+
+- Assignment (e.g. `foo.bar = '3'`)
+- Block (e.g. `foo { bar { ... } }`)
+- Include (e.g. `includeConfig 'foo.config'`)
+
+When assigning a config option, the right-hand side can be any Groovy expression, including closures which may include Groovy statements. However, only a subset of Groovy is supported within this context.
+
+Notable syntax that is supported:
+
+- numbers
+- strings
+- lists
+- maps
+- function calls
+- closures
+- variables (within closures)
+- if-else statements (within closures)
+
+Notable syntax that is not supported:
+
+- function definitions
+- class definitions
+- try-catch statements
+- lambdas (use closures instead)
+
+Other syntax restrictions:
+
+- The implicit use of environment variables is no longer supported:
+  ```groovy
+  env.MY_VAR = "$MY_VAR"                // incorrect
+  env.MY_VAR = System.getenv('MY_VAR')  // correct
+  ```
+
+- The implicit `it` variable in closures is no longer supported:
+  ```groovy
+  foo.bar = ['foo', 'bar'].collect { "--$it" }.join(' ')        // incorrect
+  foo.bar = ['foo', 'bar'].collect { it -> "--$it" }.join(' ')  // correct
+  ```

modules/nextflow/build.gradle

@@ -1,8 +1,9 @@
 apply plugin: 'groovy'
 apply plugin: 'application'
+apply plugin: 'antlr'
 
 sourceSets {
-    main.java.srcDirs = []
+    main.java.srcDirs = ['build/generated-src/antlr/main', 'src/main/antlr']
     main.groovy.srcDirs = ['src/main/java', 'src/main/groovy']
     main.resources.srcDirs = ['src/main/resources']
     test.java.srcDirs = []
@@ -15,6 +16,7 @@ compileGroovy {
 }
 
 dependencies {
+    antlr 'org.antlr:antlr4:4.9.2'
     api(project(':nf-commons'))
     api(project(':nf-httpfs'))
     api "org.apache.groovy:groovy:4.0.18"

modules/nextflow/src/main/antlr/AbstractLexer.java

@@ -0,0 +1,33 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package nextflow.antlr;
+
+import org.antlr.v4.runtime.CharStream;
+import org.antlr.v4.runtime.Lexer;
+import org.apache.groovy.parser.antlr4.SyntaxErrorReportable;
+
+/**
+ * Because antlr4 does not support generating lexer with specified interface,
+ * we have to create a super class for it and implement the interface.
+ */
+public abstract class AbstractLexer extends Lexer implements SyntaxErrorReportable {
+    public AbstractLexer(CharStream input) {
+        super(input);
+    }
+}

modules/nextflow/src/main/antlr/AbstractParser.java

@@ -0,0 +1,33 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package nextflow.antlr;
+
+import org.antlr.v4.runtime.Parser;
+import org.antlr.v4.runtime.TokenStream;
+import org.apache.groovy.parser.antlr4.SyntaxErrorReportable;
+
+/**
+ * Because antlr4 does not support generating parser with specified interface,
+ * we have to create a super class for it and implement the interface.
+ */
+public abstract class AbstractParser extends Parser implements SyntaxErrorReportable {
+    public AbstractParser(TokenStream input) {
+        super(input);
+    }
+}