Adds inline ignore functionality and unit tests. Updates the README.md file to describe how to use the new functionality. (#132)

Author: ralph-saunders

README.md

@@ -121,6 +121,15 @@ Note the (optional) `inverse_rule` attribute - this is just a convinient way to
 ## Required Instruction Section
 This section includes a list of instructions that must exist in the dockerfile in order for it to be considered valid.
 
+## Inline Ignore Instructions
+The user can tell dockerfile_lint to ignore a specific comand line inside a Dockerfile by placing a comment containing the word "dockerfile_lint" followed by the word "ignore", separated by a space, or a space and a dash/equals sign, above the command in the Dockerfile to be ignored. 
+```
+# Add is required <for some previously approved reason documented here>
+# dockerfile_lint - ignore
+ADD http://example.com/big.tar.xz /usr/src/things/
+```
+The above inline ignore would cause dockerfile_lint to skip processing the ADD command that follows it.  This allows the writing of strict rules in order to catch when best practices are not followed, while still being able to explicitly override the check on a case by case basis if a valid reason exists.  
+
 # Library Usage
 
 ## Node.js application use

lib/parser.js

@@ -9,6 +9,8 @@
 var TOKEN_WHITESPACE = RegExp(/[\t\v\f\r ]+/);
 var TOKEN_LINE_CONTINUATION = RegExp(/\\[ \t]*$/);
 var TOKEN_COMMENT = RegExp(/^#.*$/);
+// # dockerfile_lint  ignore | # dockerfile_lint  -  ignore  | # dockerfile_lint = ignore
+var TOKEN_INLINE_IGNORE = RegExp(/^#.*dockerfile_lint[ ]*\W[ ]*ignore.*$/);
 var errDockerfileNotStringArray = new Error('When using JSON array syntax, ' + 'arrays must be comprised of strings only.');
 
 
@@ -444,6 +446,7 @@ function parse(contents, options) {
     var parseResult;
     var partialLine = '';
     var includeComments = options && options['includeComments'];
+    var ignoreNextCommand = false;
 
     for (i = 0; i < lines.length; i++) {
         //LDMOD
@@ -470,9 +473,30 @@ function parse(contents, options) {
             lineno = i + 1;
         }
         parseResult = parseLine(line, lineno);
-        if (parseResult.command) {
-            if (parseResult.command.name !== 'COMMENT' || includeComments) {
-                commands.push(parseResult.command);
+        //
+        // Implement and inline ignore functionality
+        // Add a check to see if the comment contains dockerfile_lint and ignore,
+        // if it does, ignore the next command by setting a flag that we check
+        // right after calling parseLine().
+        //
+        if(parseResult.command) {
+            if (lines[i].match(TOKEN_INLINE_IGNORE)) {
+                ignoreNextCommand = true;
+            }
+            else {
+                if(parseResult.command.name !== 'COMMENT' || includeComments) {
+                    //
+                    // If an "ignore the next command comment" (i.e. an inline ignore) was found
+                    // then skip checking this command and reset the flag.
+                    //
+                    if(ignoreNextCommand === false) {
+                        commands.push(parseResult.command);
+                    }
+                    else {
+                        console.log("IGNORING STATEMENT:   " + parseResult.command.raw)
+                        ignoreNextCommand = false;
+                    }
+                }
             }
         }
         partialLine = parseResult.partialLine;

package-lock.json

@@ -50,6 +50,38 @@ describe('parse function', function () {
 
     });
 
+    it('should correctly ignore commands preceeded by an inline ignore', function () {
+        var options = {
+            includeComments: false
+        };
+        var contents = 'FROM ubuntu:latest\n'
+            + '#Comment1\n'
+            + '# dockerfile_lint - ignore\n'
+            + 'RUN echo done\n'
+            + "LABEL two=3 'one two'=4 three="
+            + '#Comment2\n'
+            + '#Comment3 \n';
+        var commands = parser.parse(contents, options);
+        commands.length.should.eql(2);
+
+    });
+
+    it('should not ignore commands preceeded by an comment about the inline ignore functionality', function () {
+        var options = {
+            includeComments: false
+        };
+        var contents = 'FROM ubuntu:latest\n'
+            + '#Comment1\n'
+            + '# dockerfile_lint comment about inline ignore\n'
+            + 'RUN echo done\n'
+            + "LABEL two=3 'one two'=4 three="
+            + '#Comment2\n'
+            + '#Comment3 \n';
+        var commands = parser.parse(contents, options);
+        commands.length.should.eql(3);
+
+    });
+
     it('should correctly report errors', function () {
         var options = {
             includeComments: false