Support negative matches

This adds support for != and !~ operators
giving more flexibility in comparing values

changelogs/unreleased/support-negative-matches.yml

+---
+title: Support negative matches
+merge_request:
+author:
+type: added

doc/ci/variables/README.md

@@ -434,8 +434,9 @@ Below you can find supported syntax reference:
 1. Equality matching using a string
 
     > Example: `$VARIABLE == "some value"`
+    > Example: `$VARIABLE != "some value"` _(added in 11.11)_
 
-    You can use equality operator `==` to compare a variable content to a
+    You can use equality operator `==` or `!=` to compare a variable content to a
     string. We support both, double quotes and single quotes to define a string
     value, so both `$VARIABLE == "some value"` and `$VARIABLE == 'some value'`
     are supported. `"some value" == $VARIABLE` is correct too.
@@ -443,22 +444,26 @@ Below you can find supported syntax reference:
 1. Checking for an undefined value
 
     > Example: `$VARIABLE == null`
+    > Example: `$VARIABLE != null` _(added in 11.11)_
 
     It sometimes happens that you want to check whether a variable is defined
     or not. To do that, you can compare a variable to `null` keyword, like
     `$VARIABLE == null`. This expression is going to evaluate to truth if
-    variable is not defined.
+    variable is not defined when `==` is used, or to falsey if `!=` is used.
 
 1. Checking for an empty variable
 
     > Example: `$VARIABLE == ""`
+    > Example: `$VARIABLE != ""` _(added in 11.11)_
 
     If you want to check whether a variable is defined, but is empty, you can
-    simply compare it against an empty string, like `$VAR == ''`.
+    simply compare it against an empty string, like `$VAR == ''` or non-empty
+    string `$VARIABLE != ""`.
 
 1. Comparing two variables
 
     > Example: `$VARIABLE_1 == $VARIABLE_2`
+    > Example: `$VARIABLE_1 != $VARIABLE_2` _(added in 11.11)_
 
     It is possible to compare two variables. This is going to compare values
     of these variables.
@@ -477,9 +482,11 @@ Below you can find supported syntax reference:
 1. Pattern matching  _(added in 11.0)_
 
     > Example: `$VARIABLE =~ /^content.*/`
+    > Example: `$VARIABLE_1 !~ /^content.*/` _(added in 11.11)_
 
     It is possible perform pattern matching against a variable and regular
-    expression. Expression like this evaluates to truth if matches are found.
+    expression. Expression like this evaluates to truth if matches are found
+    when using `=~`. It evaluates to truth if matches are not found when `!~` is used.
 
     Pattern matching is case-sensitive by default. Use `i` flag modifier, like
     `/pattern/i` to make a pattern case-insensitive.

lib/gitlab/ci/pipeline/expression/lexeme/not_equals.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module Pipeline
+      module Expression
+        module Lexeme
+          class NotEquals < Lexeme::Operator
+            PATTERN = /!=/.freeze
+
+            def initialize(left, right)
+              @left = left
+              @right = right
+            end
+
+            def evaluate(variables = {})
+              @left.evaluate(variables) != @right.evaluate(variables)
+            end
+
+            def self.build(_value, behind, ahead)
+              new(behind, ahead)
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/gitlab/ci/pipeline/expression/lexeme/not_matches.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module Pipeline
+      module Expression
+        module Lexeme
+          class NotMatches < Lexeme::Operator
+            PATTERN = /\!~/.freeze
+
+            def initialize(left, right)
+              @left = left
+              @right = right
+            end
+
+            def evaluate(variables = {})
+              text = @left.evaluate(variables)
+              regexp = @right.evaluate(variables)
+
+              regexp.scan(text.to_s).none?
+            end
+
+            def self.build(_value, behind, ahead)
+              new(behind, ahead)
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/gitlab/ci/pipeline/expression/lexer.rb

@@ -15,7 +15,9 @@ module Gitlab
             Expression::Lexeme::Pattern,
             Expression::Lexeme::Null,
             Expression::Lexeme::Equals,
-            Expression::Lexeme::Matches
+            Expression::Lexeme::Matches,
+            Expression::Lexeme::NotEquals,
+            Expression::Lexeme::NotMatches
           ].freeze
 
           MAX_TOKENS = 100

lib/gitlab/ci/pipeline/expression/statement.rb

@@ -8,13 +8,24 @@ module Gitlab
           StatementError = Class.new(Expression::ExpressionError)
 
           GRAMMAR = [
+            # presence matchers
             %w[variable],
+
+            # positive matchers
             %w[variable equals string],
             %w[variable equals variable],
             %w[variable equals null],
             %w[string equals variable],
             %w[null equals variable],
-            %w[variable matches pattern]
+            %w[variable matches pattern],
+
+            # negative matchers
+            %w[variable notequals string],
+            %w[variable notequals variable],
+            %w[variable notequals null],
+            %w[string notequals variable],
+            %w[null notequals variable],
+            %w[variable notmatches pattern]
           ].freeze
 
           def initialize(statement, variables = {})

spec/lib/gitlab/ci/pipeline/expression/lexeme/not_equals_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Ci::Pipeline::Expression::Lexeme::NotEquals do
+  let(:left) { double('left') }
+  let(:right) { double('right') }
+
+  describe '.build' do
+    it 'creates a new instance of the token' do
+      expect(described_class.build('!=', left, right))
+        .to be_a(described_class)
+    end
+  end
+
+  describe '.type' do
+    it 'is an operator' do
+      expect(described_class.type).to eq :operator
+    end
+  end
+
+  describe '#evaluate' do
+    it 'returns true when left and right are not equal' do
+      allow(left).to receive(:evaluate).and_return(1)
+      allow(right).to receive(:evaluate).and_return(2)
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate(VARIABLE: 3)).to eq true
+    end
+
+    it 'returns false when left and right are equal' do
+      allow(left).to receive(:evaluate).and_return(1)
+      allow(right).to receive(:evaluate).and_return(1)
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate(VARIABLE: 3)).to eq false
+    end
+  end
+end

spec/lib/gitlab/ci/pipeline/expression/lexeme/not_matches_spec.rb

+require 'fast_spec_helper'
+require_dependency 're2'
+
+describe Gitlab::Ci::Pipeline::Expression::Lexeme::NotMatches do
+  let(:left) { double('left') }
+  let(:right) { double('right') }
+
+  describe '.build' do
+    it 'creates a new instance of the token' do
+      expect(described_class.build('!~', left, right))
+        .to be_a(described_class)
+    end
+  end
+
+  describe '.type' do
+    it 'is an operator' do
+      expect(described_class.type).to eq :operator
+    end
+  end
+
+  describe '#evaluate' do
+    it 'returns true when left and right do not match' do
+      allow(left).to receive(:evaluate).and_return('my-string')
+      allow(right).to receive(:evaluate)
+        .and_return(Gitlab::UntrustedRegexp.new('something'))
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate).to eq true
+    end
+
+    it 'returns false when left and right match' do
+      allow(left).to receive(:evaluate).and_return('my-awesome-string')
+      allow(right).to receive(:evaluate)
+        .and_return(Gitlab::UntrustedRegexp.new('awesome.string$'))
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate).to eq false
+    end
+
+    it 'supports matching against a nil value' do
+      allow(left).to receive(:evaluate).and_return(nil)
+      allow(right).to receive(:evaluate)
+        .and_return(Gitlab::UntrustedRegexp.new('pattern'))
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate).to eq true
+    end
+
+    it 'supports multiline strings' do
+      allow(left).to receive(:evaluate).and_return <<~TEXT
+        My awesome contents
+
+        My-text-string!
+      TEXT
+
+      allow(right).to receive(:evaluate)
+        .and_return(Gitlab::UntrustedRegexp.new('text-string'))
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate).to eq false
+    end
+
+    it 'supports regexp flags' do
+      allow(left).to receive(:evaluate).and_return <<~TEXT
+        My AWESOME content
+      TEXT
+
+      allow(right).to receive(:evaluate)
+        .and_return(Gitlab::UntrustedRegexp.new('(?i)awesome'))
+
+      operator = described_class.new(left, right)
+
+      expect(operator.evaluate).to eq false
+    end
+  end
+end

spec/lib/gitlab/ci/pipeline/expression/statement_spec.rb

@@ -101,6 +101,18 @@ describe Gitlab::Ci::Pipeline::Expression::Statement do
       "$EMPTY_VARIABLE =~ /var.*/"         | false
       "$UNDEFINED_VARIABLE =~ /var.*/"     | false
       "$PRESENT_VARIABLE =~ /VAR.*/i"      | true
+      '$PRESENT_VARIABLE != "my variable"' | false
+      '"my variable" != $PRESENT_VARIABLE' | false
+      '$PRESENT_VARIABLE != null'          | true
+      '$EMPTY_VARIABLE != null'            | true
+      '"" != $EMPTY_VARIABLE'              | false
+      '$UNDEFINED_VARIABLE != null'        | false
+      'null != $UNDEFINED_VARIABLE'        | false
+      "$PRESENT_VARIABLE !~ /var.*e$/"     | false
+      "$PRESENT_VARIABLE !~ /^var.*/"      | true
+      "$EMPTY_VARIABLE !~ /var.*/"         | true
+      "$UNDEFINED_VARIABLE !~ /var.*/"     | true
+      "$PRESENT_VARIABLE !~ /VAR.*/i"      | false
     end
 
     with_them do